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Acquisition of polarized-light orientation in salmonids under laboratory conditions
Abstract
We examined orientation responses of juvenile salmonids to a polarized-light stimulus under laboratory conditions. Juvenile rainbow trout, Oncorhynchus mykiss, steelhead (anadromous), O. mykiss, and brook char, Salvelinus fontinalis, were trained using an operant conditioning methodology to orient relative to the axis of a linear-polarized light field. On average, rainbow trout responded correctly relative to the orientation of the light stimulus approximately 70% of the time within five training sessions. The proportion of correct responses increased further under an intermittent reinforcement schedule. We released trained and untrained fish individually in a circular tank and quantified orientation responses using a digital image-tracking system. Experimentally naı̈ve rainbow trout had no directional tendency, in contrast to trained rainbow trout, steelhead and brook char, which oriented relative to the plane of polarized light. Trained fish showed no orientation response when a diffuser was used to depolarize the light source. Rainbow trout trained to orient parallel to a polarization axis in the laboratory were tested under natural skylight before sunset. These fish oriented parallel to the bearing of maximally polarized light in the celestial hemisphere. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.
... (c) Spatial orientation Hawryshyn and co-workers trained fish to perform a goal-oriented behaviour using polarization cues [24,39]. Fishes actively navigate during the spatial orientation response by adjusting ongoing movements in response to polarized light cues. ...
... Fishes actively navigate during the spatial orientation response by adjusting ongoing movements in response to polarized light cues. Recent work on the spatial orientation of rainbow trout used video recording to examine the angular responses of fishes to imposed polarized light cues [39]. These recordings show that the spontaneous orientation of fishes to e-vector is highly dynamic. ...
... Trout circle and scan the overhead polarization with side-to-side head movements (up to 1808) and dynamically change their body axis relative to the polarization cue. Trout that have been trained in the laboratory and tested outdoors using natural polarization cues show very robust spatial orientation responses, illustrating that this behaviour generalizes well to natural polarization cues [39]. It has been suggested that the cues they use are polarization cues present in the celestial hemisphere [24,39,40]. ...
In this review, we will discuss the recent literature on fish polarization vision and we will present a model on how the retina processes polarization signals. The model is based on a general retinal-processing scheme and will be compared with the available electrophysiological data on polarization processing in the retina. The results of this model will help illustrate the functional significance of polarization vision for both feeding behaviour and navigation. First, we examine the linkage between structure and function in polarization vision in general.
... The overall sensitivity to the background light field is probably adjusted through the SWS cones (moderating spectral brightness differences), in a manner comparable to the polarizationinsensitive long UV receptor (twisted) of honeybees (Bernard and Wehner, 1977), thus permitting the vertical and horizontal polarization detector mechanisms to operate at a higher signalto noise ratio. Our experimental work on spatial orientation behavior in Pacific salmonids shows that the SWS cones in addition to the UVS cones must be stimulated to achieve high fidelity spatial orientation responses Parkyn et al., 2003). ...
... Fish have been shown to use UV reflectance patterns in intraspecific communication most notably mate choice (Macias Garcia and Burt de Perera, 2002;Rick et al., 2006;Siebeck et al., 2010;White et al., 2003), so it probable that UV PS plays an important role in enhancing these body patterns. Salmonids use UV polarization sensitivity to guide spatial orientation to polarized light fields Hawryshyn and Bolger, 1990;Parkyn et al., 2003). We also know that when anadromy evolved in the Salmoninae, the ancestor had UV PS, an attribute known to guide spatial orientation. ...
... We also know that when anadromy evolved in the Salmoninae, the ancestor had UV PS, an attribute known to guide spatial orientation. We do not claim that UV PS and anadromy are dependent on one another but we note that there is strong evidence for polarization-guided spatial orientation in salmonid fishes Parkyn et al., 2003), which is important for navigation in migrating salmonids. Other taxa that possess UV PS probably share the capacity to use UV polarization in local or more global spatial orientation tasks. ...
We were interested in comparing the characteristics of polarization sensitivity in Atlantic salmon to those in Pacific salmon. Here we show that the common ancestor to the clade containing Salmo salar, Oncorhynchus mykiss, O. nerka, O. clarkii and Salvelinus fontinalis has the trait of ultraviolet polarization sensitivity. We examined spectral and polarization sensitivity of juvenile Atlantic salmon (Salmo salar) using both optic nerve compound action potential (CAP) and electroretinogram (ERG) recordings. Our experiments employed photic manipulation to adjust the sensitivity of the four cone mechanisms of Atlantic salmon. A spectrally broad background was used to ensure a contribution of all cone mechanisms to both spectral and polarization sensitivity. Chromatic adaptation was used to isolate the sensitivity of each of the four cone mechanisms for both spectral and polarization sensitivity. Under spectrally broad conditions, UV sensitive (UVS), mid wavelength sensitive (MWS) and long wavelength sensitive (LWS) cone mechanisms contributed to polarization sensitivity. CAP recordings produced the typical 'W' shaped polarization sensitivity curve reflecting two active polarization detectors with peaks at e-vector orientations of 0 deg, 90 deg and 180 deg, and troughs at 30 deg and 150 deg. ERG recordings produced a four-peaked polarization sensitivity curve reflecting two active polarization detectors and negative feedback activity, with peaks at e-vectors 0 deg, 45 deg, 90 deg, 135 deg and 180 deg, and troughs at 30 deg, 60 deg, 120 deg and 150 deg. Polarization-sensitivity measurements of isolated cone mechanisms revealed two orthogonal polarization detector mechanisms in Atlantic salmon, identical to that found in rainbow trout and other Pacific salmonid fishes. Moreover, under spectrally broad background conditions, CAP and ERG polarization sensitivity of Atlantic salmon did not differ significantly from that reported in Pacific salmonids.
... But do these studies provide meaningful information about the spatial orientation behavior of fish to polarized light in the visual environment? Recent work on the spatial orientation of rainbow trout (Oncorhynchus mykiss) used video recording to examine the angular responses of fish to imposed polarized light cues [Parkyn et al., 2003]. These recordings show that the spontaneous orientation of fish to e-vector is highly dynamic. ...
... These recordings show that the spontaneous orientation of fish to e-vector is highly dynamic. Fish typically circle and scan the overhead polarization with side to side head movements (up to 180°) and dynamically change their body axis relative to the polarization cue [Parkyn et al., 2003]. Therefore, the observation that Zenarchopterus spp. ...
... Orientation of Naïve Fish . Although trained trout demonstrated the ability to orient relative to the imposed e-vector, untrained rainbow trout lacked a common directional response [Parkyn et al., 2003]. There was no alignment of trout to the imposed e-vector, which may be a result of the innate spontaneous orientation seen in other species of fish [e.g. ...
Teleost fishes are capable of detecting and behaviorally responding to linearly polarized light. Fish exhibit free-swimming spatial orientation to imposed and natural polarized light fields, and the fidelity of this spatial orientation depends heavily on UV and short wavelength content of the polarization field. Fish make fine-scale behavioral discriminations between stimuli that differ in e-vector orientation, independent of brightness. The detection of polarized light by photoreceptors is based on specializations of the disk membrane in the outer segment of cones that permit preferential absorption of axial and transverse polarized light. Differential polarization detectors that have overlapping spectral sensitivity in the UV short wavelength spectrum mediate polarization sensitivity. These differential detectors are based on cone photoreceptors that share spectral sensitivity in the UV short wavelength spectrum: the alpha-band of UV-sensitive cone mechanism as the vertical detector, and the beta-band of mid- and long-wavelength sensitive cone mechanisms as the horizontal detector. Negative feedback of horizontal cells on cones govern opponent interactions between differentially sensitive polarization detectors. Polarization opponency functions to enhance e-vector contrast under conditions that vary in degree of polarization and ambient intensity. Ontogenetic changes in the cone mosaic, resulting from programmed cell death and regeneration of UV-sensitive cones, alter the retinal location of polarization sensitivity. These developmental changes greatly influence behavioral responses to polarized light.
... The visual world of fish is a complex environment, where colour, intensity and polarization of light are available to guide behaviours (Cronin and Shashar, 2001;Parkyn et al., 2003;Novales Flamarique and Hawryshyn, 1997;McFarland and Munz, 1975a;Pomozi et al., 2001). The complexity of the underwater photic environment is mirrored by the diversity of visual adaptations that have evolved to perceive these qualities of light (Barry and Hawryshyn, 1999;McFarland and Munz, 1975b;Novales Flamarique and Hawryshyn, 1993). ...
... The complexity of the underwater photic environment is mirrored by the diversity of visual adaptations that have evolved to perceive these qualities of light (Barry and Hawryshyn, 1999;McFarland and Munz, 1975b;Novales Flamarique and Hawryshyn, 1993). Many species of fish have evolved visual mechanisms for the perception of linearly polarized light and behaviours based on this perception, such as spatial orientation behaviour for either laboratory or natural illumination experiments (Hawryshyn and McFarland, 1987;Hawryshyn et al., 2003;Parkyn and Hawryshyn, 2000;Parkyn et al., 2003;Mussi et al., 2005;Shashar and Cronin, 1996;Shashar et al., 1998;Shashar et al., 2001;Shashar and Hanlon, 1997;Waterman and Hashimoto, 1974). ...
... A number of techniques have been used to examine polarization sensitivity (PS) in several teleost species including: heart rate conditioning (Hawryshyn and McFarland, 1987), single unit recording from the torus semicircularis (Coughlin and Hawryshyn, 1995) and the optic tectum (Waterman and Hashimoto, 1974), compound action potential (CAP) recordings from the optic nerve Retinal processing and polarization sensitivity (Parkyn and Hawryshyn, 1993;Parkyn and Hawryshyn, 2000), electroretinograms (ERGs) and behavioural orientation and discrimination paradigms (Hawryshyn et al., 1990;Parkyn et al., 2003;Degner and Hawryshyn, 2001;Mussi et al., 2005). However, examinations of the neuronal pathways underlying PS have been restricted to several species of cyprinids and salmonids. ...
A number of teleost fishes have photoreceptor mechanisms to detect linearly polarized light. We studied the neuronal mechanism underlying this ability. It was found that a polarized signal could be detected in rainbow trout (Oncorhynchus mykiss) both in the electroretinogram (ERG) and in the compound action potential (CAP) measured in the optic nerve, indicating a strong retinal contribution to the processing of polarized light. The CAP recordings showed a W-shaped sensitivity curve, with a peak at 0 degrees , 90 degrees and 180 degrees , consistent with processes for both vertical and horizontal orientation. By contrast, the ERG recordings reveal a more complex pattern. In addition to the peaks at 0 degrees , 90 degrees and 180 degrees , two additional peaks appeared at 45 degrees and 135 degrees . This result suggests a specialized contribution of the outer retina in the processing of polarized light. The spectral sensitivity of the mechanisms responsible for these intermediate peaks was studied using chromatic adaptation. Here we show that long wavelength-sensitive (LWS) cone mechanism adaptation shifted the intermediate peaks towards 90 degrees , whereas ultraviolet-sensitive (UVS) cone mechanism adaptation shifted the peaks away from 90 degrees towards either 0 degrees or 180 degrees . These results provide further confirmation that the 90 degrees peak is dominated by the LWS cone mechanism and the 0 degrees and 180 degrees peaks are dominated by the UVS cone mechanism. In addition, a pharmacological approach was used to examine the retinal neural mechanisms underlying polarization sensitivity. The effect of blocking negative feedback from horizontal cells to cones on the ERG was studied by making intraocular injections of low doses of cobalt, known to block this feedback pathway. It was found that the intermediate peaks seen in the ERG polarization sensitivity curves were eliminated after application of cobalt, suggesting that these peaks are due to outer retinal inhibition derived from feedback of horizontal cells onto cones. A simple computational model was developed to evaluate these results. The model consists of opponent and non-opponent processing elements for the two polarization detectors. This model provides a first approximation analysis suggesting that opponent processing occurs in the outer retina for polarization vision. Although it seems that polarization vision uses a slightly more complicated coding scheme than colour vision, the results presented in this paper suggest that opponent and non-opponent channels process polarization information.
... A bioinspired underwater navigation technology, named artificial lateral line system, is proposed in [9], where the 3-D motion can be estimated by solving the pressure variation model of the surrounding flow field. Aquatic animals, such as mantis shrimps [10], [11] and rainbow trouts [12], have been found to use the underwater polarization field to determine their body orientation. The navigational means by using the underwater natural light fields [13] is also fully autonomous. ...
... The zenith vector is used to calculate horizontal attitude angles of pitch and roll, as shown in (14). Afterward, pitch and roll can be used to represent the ATM from h-frame to b-frame by (12). Its transposed matrix (16). ...
Underwater autonomous navigation has long been a challenging problem due to the scarcity of information sources. The polarization navigation offers a feasible solution to this problem. The existing polarization navigation schemes, however, require that the horizontal attitude is known, which can only be used for two-dimensional orientation. To address the limitation, a three-dimensional (3D) attitude determination strategy is developed in this article by exploiting the underwater downwelling radiance fields (light intensity and polarization). In particular, the horizontal attitude information contained in the Snell's window, a unique underwater optical phenomenon induced by refraction, is extracted via an improved edge recognition method. On this basis, underwater polarization is exploited to calculate solar position for orientation. By this means, the 3D attitude is acquired independently using underwater downwelling radiance fields. The effectiveness of the proposed strategy is validated via experiments in both water tank and open sea environments.
... A test of foraging and prey-selection under polarized light by rainbow trout found prey were detected at greater distances under polarized light compared to unpolarized lights (Novales-Flamarique and Browman 2001). In another study, juvenile rainbow trout, steelhead, and brook trout were trained to orient relative to the axis of polarized light (Parkyn et al. 2003); however, untrained fish showed no orientation response. ...
... All species were sensitive to UV radiation. Parkyn DC, JD Austin, and CW Hawryshyn (2003) To test whether hatcheryreared rainbow trout would orient to a plane-polarized light; to compare orientation responses of potamodromous vs. anadromous salmonids; and to examine the orientation response of laboratorytrained rainbow trout relative to natural polarized light Rainbow trout, steelhead, brook char ...
The goal of the study described in this report is to provide U.S. Army Corps of Engineers (USACE) biologists and engineers with general design guidelines for using artificial lighting to enhance the passage of juvenile salmonids into the collection channel at the Bonneville Dam second powerhouse (B2). During fall 2007, Pacific Northwest National Laboratory (PNNL) researchers measured light levels in the field at one powerhouse orifice through which fish must pass to reach the collection channel. Two light types were evaluatedlight-emitting diode (LED) lights and halogen spot lights. Additional measurements with mercury lamps were made at the PNNL Aquatic Research Laboratory to determine baseline intensity of the current lighting. A separate chapter synthesizes the relevant literature related to light and fish guidance for both field and laboratory studies. PNNL will also review the Corps plans for existing lighting protocol at all of the Portland District projects and help develop a uniform lighting scheme which could be implemented. The specific objectives for this study are to 1. Create a synthesis report of existing lighting data for juvenile salmonid attraction and deterrence and how the data are used at fish bypass facilities. 2. Evaluate current B2 orifice lighting conditions with both LED and halogen sources. 3. Make recommendations as to what lighting intensity, source, and configuration would improve passage at the B2 orifices. 4. Review USACE plans for retrofit of existing systems (to be assessed at a later date).
... Similar to Section V-C, analyzing the noise sensitivity yields the noise STD of the recovered distance as (45) Equation (45) indicates that this noise is greatly amplified if . Recall that the illumination of scenes at deeper water typically suffers from low energy in the red portion of the spectrum, thus . ...
... Similar to Section V-C, analyzing the noise sensitivity yields the noise STD of the recovered distance as (45) Equation (45) indicates that this noise is greatly amplified if . Recall that the illumination of scenes at deeper water typically suffers from low energy in the red portion of the spectrum, thus . ...
Underwater imaging is important for scientific research and technology as well as for popular activities, yet it is plagued by poor visibility conditions. In this paper, we present a computer vision approach that removes degradation effects in underwater vision. We analyze the physical effects of visibility degradation. It is shown that the main degradation effects can be associated with partial polarization of light. Then, an algorithm is presented, which inverts the image formation process for recovering good visibility in images of scenes. The algorithm is based on a couple of images taken through a polarizer at different orientations. As a by-product, a distance map of the scene is also derived. In addition, this paper analyzes the noise sensitivity of the recovery. We successfully demonstrated our approach in experiments conducted in the sea. Great improvements of scene contrast and color correction were obtained, nearly doubling the underwater visibility range.
... This migratory behavior (especially upon entering estuaries and near shore regions in anadromous populations) would benefit from the ability to orient relative to natural polarized light patterns, an ability seemingly lacking in smolts. Interestingly, previous studies measured the orientation responses of trout to polarized light stimuli that arrived from above and mainly illuminated the ventral retina (Hawryshyn and Bolger, 1990;Hawryshyn et al., 1990;Degner and Hawryshyn, 2001;Parkyn et al., 2003), suggesting no PS in the ventral retina of smolts. Is it possible that smolts are capable of PS via their dorsal rather than the ventral retina and, if so, what mechanism would allow such an ontogenetic change in PS? ...
... The shallow-swimming parr are able to orient relative to polarized light patterns that are incident from above and illuminate the ventral retina (Hawryshyn and Bolger, 1990;Degner and Hawryshyn, 2001;Parkyn et al., 2003), suggesting that parr may use the celestial polarization pattern for orientation. In contrast, smolts reside in deeper water, where the celestial polarization pattern becomes distorted and unreliable due to polarization decay when celestial light is transmitted through water. ...
Polarization sensitivity (PS) in vertebrate vision is controversial, perhaps because its underlying mechanism has remained obscure. An issue that might have added to the controversy is that rainbow trout (Oncorhynchus mykiss), which have served as the primary model system for polarization-based orientation, lose their ability to orient relative to celestial polarized-light patterns when parr (fry) transform into migratory smolts (juveniles), which would benefit most from polarization-based orientation. Here we addressed two key questions: (1) what is the mechanism underling PS?, and (2) how can the paradoxical loss of PS in trout smolts be reconciled? We assessed PS from optic nerve recordings in parr and smolts and found that the retinal region with enhanced PS shifted from the ventral retina in parr to the dorsal retina in smolts. This adaptation may allow fish to use the most reliable polarization field encountered at each life stage, the celestial polarization field in the shallow-swimming parr and the depth-insensitive underwater polarization field in the deep-swimming smolts. In addition, we assessed spectral sensitivity across the retina and during ontogeny and fit a cascade retinal model to PS data. We found that differential contribution of two cone detectors with orthogonal PS could drive the variation in PS and that feedback from horizontal cells to cones could explain the differential amplification of PS. This elegant arrangement, in which weak PS of cones is amplified and tuned by retinal networks, allows for PS without interfering with sampling of other visual information and illustrates how sensory systems may simultaneously process disparate aspects of physical environments.
... In fact, training began using 15 fish; six fish died and five fish failed to learn the task. Four fish were used in this study, which is typical in behavioural discrimination experiments, given the length of experimentation required to assess visual performance for an individual fish (Neumeyer, 1984(Neumeyer, , 2003Degner and Hawryshyn, 2001;Parkyn et al., 2003). ...
... The use of the 450·nm long-pass filter demonstrates the critical role played by the UV portion of the spectrum for polarization vision; when UVS cones were not stimulated, fish were incapable of discriminating between e-vectors. Similar conclusions were found in salmonids Degner and Hawryshyn, 2001;Parkyn et al., 2003). In Hawryshyn et al. (2003), a UV-transmitting filter (Shott; UG-11; Corion Spectra Physics) was used to produce UVS cone chromatic adaptation. ...
In this study, we demonstrate the capacity for damselfish (green chromis, Chromis viridis) to discriminate between different e-vector orientations of ultraviolet polarized light. We examined the ability of green chromis to resolve small differences in e-vector orientation of ultraviolet polarized light. Fish were successfully trained to swim towards an e-vector orientation of polarized light using a behavioural chamber. C. viridis was able to discriminate between the horizontal and the vertical plane of ultraviolet polarized light independent of brightness content of the stimuli. However, e-vector discrimination capability disappeared when the ultraviolet portion of the light stimuli was removed, indicating that the presence of ultraviolet light was critical for e-vector discrimination. Fish could also distinguish between relatively small e-vector orientations of ultraviolet polarized light. Functional implications for high e-vector discriminative capabilities could be used in functional domains such as feeding and communication.
... Among them, a grass shrimp named Palaemonetes vulgaris (Goddard and Forward, 1991;Horváth and Varjú, 1995) can perceive the underwater polarization pattern in Snell's window and uses this pattern as a direction cue to move away from the coastline predators. In the process of migration, rainbow trout (Hawryshyn and Bolger, 1990;Browman and Hawryshyn, 1994;Parkyn et al., 2003) can make use of underwater polarization patterns to realize navigation. The vision system of mantis shrimp (Bok et al., 2014;Gagnon et al., 2015) can detect and analyze visible light, ultraviolet light, linearly and circularly polarized light, which enables it to accurately capture prey, avoid natural enemies, and even navigate in the underwater environment with low illumination, strong scattering, and high turbidity. ...
Aiming at the requirement of autonomous navigation capability of the underwater unmanned vehicle (UUV), a novel bionic method for underwater navigation based on polarization pattern within Snell’s window is proposed. Inspired by creatures, polarization navigation is a satellite-free navigation scheme and has great potential to be used in the water. However, because of the complex underwater environment, whether UUV polarization navigation can be realized is doubtful. To illustrate the feasibility of underwater polarization navigation, we firstly establish the model of underwater polarization patterns to prove the stability and predictability of the underwater polarization pattern within Snell’s window. Then, we carry out static and dynamic experiments of underwater heading determination based on developed polarization information detection equipment. Finally, we obtain underwater polarization patterns and conduct the tracking experiment at different water depths. The experimental results of the underwater polarization patterns are consistent with the simulation, which proves the correctness of the proposed model. At the water depth of 5 m, the average angle and position error of the tracking experiment are 14.3508° and 4.0812 m, respectively. It is illustrated that underwater polarization navigation is realizable and the precision can meet the real-time navigation requirements of UUV. This study promotes the improvement of underwater navigation ability and the development of marine equipment.
... olfactory cues alone are insufficient to influence migrations that can span upwards of 1000 km from the open ocean to near-coastal waters or vice versa(Lohmann & Lohmann, 2019). Long-distance migrations, such as those undertaken by various salmonids, thunnids, as well as anguillid eels, are presumably initiated by geomagnetic sense, as well as environmental cues, and are possibly further enhanced by the use of celestial and visual cues, such as the sun compass and the polarization of light(Hawryshyn, 1992;Parkyn et al., 2003;Naisbett-Jones et al., 2017). In relation to the lifetime of most fish, the Earth's geomagnetic field may serve as a reasonably constant and reliable source of directional and positional information(Formicki et al., 2019), which exists everywhere on Earth, is present day and night, and is largely unaffected by weather(Johnsen et al., 2020).Diverse mechanisms have been proposed as the basis for detecting magnetic fields: electromagnetic induction (possible in elasmobranchs via the ampullae of Lorenzini), magnetic-field-dependent chemical reactions (hypothesized in terrestrial vertebrates) and biogenic magnetite crystal-based magnetoreception (hypothesized in fishes in which magnetite crystals have been found, such as salmonids;Johnsen & Lohmann, 2005). ...
Movement of fishes in the aquatic realm is fundamental to their ecology and survival. Movement can be driven by a variety of biological, physiological and environmental factors occurring across all spatial and temporal scales. The intrinsic capacity of movement to impact fish individually (e.g., foraging) with potential knock‐on effects throughout the ecosystem (e.g., food web dynamics) has garnered considerable interest in the field of movement ecology. The advancement of technology in recent decades, in combination with ever‐growing threats to freshwater and marine systems, has further spurred empirical research and theoretical considerations. Given the rapid expansion within the field of movement ecology and its significant role in informing management and conservation efforts, a contemporary and multidisciplinary review about the various components influencing movement is outstanding. Using an established conceptual framework for movement ecology as a guide (i.e., Nathan et al., 2008: 19052), we synthesized the environmental and individual factors that affect the movement of fishes. Specifically, internal (e.g., energy acquisition, endocrinology, and homeostasis) and external (biotic and abiotic) environmental elements are discussed, as well as the different processes that influence individual‐level (or population) decisions, such as navigation cues, motion capacity, propagation characteristics and group behaviours. In addition to environmental drivers and individual movement factors, we also explored how associated strategies help survival by optimizing physiological and other biological states. Next, we identified how movement ecology is increasingly being incorporated into management and conservation by highlighting the inherent benefits that spatio‐temporal fish behaviour imbues into policy, regulatory, and remediation planning. Finally, we considered the future of movement ecology by evaluating ongoing technological innovations and both the challenges and opportunities that these advancements create for scientists and managers. As aquatic ecosystems continue to face alarming climate (and other human‐driven) issues that impact animal movements, the comprehensive and multidisciplinary assessment of movement ecology will be instrumental in developing plans to guide research and promote sustainability measures for aquatic resources.
... The northern anchovy is one of the only vertebrates for which there is a satisfying physiological explanation (Flamarique and Hárosi, 2002;Flamarique, 2019). However, behavioral evidence suggests the occurrence of widespread polarization sensitivity in vertebrates (Hawryshyn and McFarland, 1987;Coughlin and Hawryshyn, 1995;Kamermans and Hawryshyn, 2011;Parkyn et al., 2003;Calabrese et al., 2014;Horváth and Varju, 2004). Based on these studies, it is likely that at least some GZP predators have polarization visual sensitivity and how those organisms view plastic would have substantial impacts on plastic ingestion. ...
Plastic pollution in the ocean is an increasingly detrimental issue for marine organisms. As a form of polarized light pollution, transparent plastic debris may be more visible and pose additional threats to organisms that can detect and interpret polarized light. Plastic can mimic the visual features of common marine prey items, such as transparent gelatinous zooplankton, which may lead to more significant plastic ingestion. We measured, in situ, the polarization and radiance contrast between a transparent plastic bag and gelatinous zooplankton with an underwater video polarimeter. The plastic bag had significantly higher polarization contrast than the gelatinous zooplankton, yet both shared similar radiance contrasts. This higher polarization contrast may contribute to the observed high ingestion rates of transparent plastic by marine organisms. Further study into the connection between polarization-sensitive organisms and plastic ingestion is recommended.
... Similar to the on-land scenarios the information for underwater navigation is provided by the so-called Underwater Polarization Pattern (UPP) which describes the spatial distribution of polarized light and is highly correlated with the solar position 8 . In fact, it has been revealed that several aquatic animals can detect polarized light for underwater navigation 9,10 . Mantis shrimps can perceive polarized light and use them to navigate back to home after foraging 11,12 . ...
Underwater navigation system is an indispensable part for autonomous underwater vehicles. Due to the indiscernibility of satellite signal, however, the underwater navigation problem is quite challenging, and a satellite-free navigation scheme should be looked for. Polarization navigation, inspired by insects’ capability of autonomous homing and foraging, is an alternative solution to satellite navigation with great application potential. Underwater polarization provides an indirect sun compass to animals for orientation determination. However, it is difficult to apply terrestrial solar-tracking methodologies in underwater situations due to the refraction of polarized skylight at the air-water interface. To resolve this issue, an underwater solar-tracking algorithm is developed based on the underwater refraction-polarization pattern inside the Snell's window. By employing Snell's law and Fresnel refraction formula to decouple the refractive ray bending and polarization deflection, the celestial polarization pattern is obtained based on underwater measurement. To further improve the accuracy, the degree of polarization is employed as a weight factor for E-vector. A long-lasting underwater experiment was conducted to validate the effectiveness of the proposed approach, and the results showed the root-mean-square errors of solar zenith and azimuth employing this algorithm were 0.3° and 1.3°, respectively. Our experimental results show that the refraction-polarization pattern inside the Snell's window exhibits immense potential to improve the solar-tracking accuracy for underwater navigation.
... Polarised light may also provide information about more broad-field environmental cues than those mentioned above. The best studied example is the incorporation of information from polarised skylight into the celestial compass of many insect species (reviews: Wehner 2001; Horváth and Varjú 2004;Horváth et al. 2014), a capacity that has also been suggested in some crustacean (Bainbridge and Waterman 1957) and mollusc species (Jander et al. 1963), and even some vertebrates (Taylor and Adler 1973;Able and Able 1993;Parkyn et al. 2003). Since the pattern of polarised skylight indicates the sun's compass bearing (the solar azimuth), it may be used as a reference frame for geographic body-axis orientation when the sun is not visible. ...
In recent years, the study of polarization vision in animals has seen numerous breakthroughs, not just in terms of what is known about the function of this sensory ability, but also in the experimental methods by which polarization can be controlled, presented and measured. Once thought to be limited to only a few animal species, polarization sensitivity is now known to be widespread across many taxonomic groups, and advances in experimental techniques are, in part, responsible for these discoveries. Nevertheless, its study remains challenging, perhaps because of our own poor sensitivity to the polarization of light, but equally as a result of the slow spread of new practices and methodological innovations within the field. In this review, we introduce the most important steps in designing and calibrating polarized stimuli, within the broader context of areas of current research and the applications of new techniques to key questions. Our aim is to provide a constructive guide to help researchers, particularly those with no background in the physics of polarization, to design robust experiments that are free from confounding factors.
... While at sea, homing salmon navigate by an array of stimuli including magnetic field (Putman et al., 2013), polarized light (Parkyn, Austin, & Hawryshyn, 2003), and scent trails from conspecifics (Nordeng, 1971). When approaching coastal areas and once being in the freshwater system, navigation is based primarily on stream-specific scents that are picked up by the olfactory sense (Bett & Hinch, 2016). ...
Abstract The anadromous salmon life cycle includes two migratory events, downstream smolt migration and adult homing migration, during which they must navigate with high precision. During homing migration, olfactory cues are used for navigation in coastal and freshwater areas, and studies have suggested that the parr–smolt transformation has a sensitive period for imprinting. Accordingly, we hypothesized that there would be significant changes in gene expression in the olfactory epithelium specifically related to smoltification and sampled olfactory rosettes from hatchery‐reared upper growth modal juvenile Atlantic salmon at 3‐week intervals from January to June, using lower growth modal nonsmolting siblings as controls. A suite of olfactory receptors and receptor‐specific proteins involved in functional aspects of olfaction and peripheral odor memorization was analyzed by qPCR. Gene expression in juveniles was compared with mature adult salmon of the same genetic strain caught in the river Gudenaa. All mRNAs displayed significant variation over time in both modal groups. Furthermore, five receptor genes (olfc13.1, olfc15.1, sorb, ora2, and asor1) and four olfactory‐specific genes (soig, ependymin, gst, and omp2) were differentially regulated between modal groups, suggesting altered olfactory function during smoltification. Several genes were differentially regulated in mature salmon compared with juveniles, suggesting that homing and odor recollection involve a different set of genes than during imprinting. Thyroid hormone receptors thrα and thrβ mRNAs were elevated during smolting, suggesting increased sensitivity to thyroid hormones. Treatment of presmolts with triiodothyronine in vivo and ex vivo had, however, only subtle effects on the investigated olfactory targets, questioning the hypothesis that thyroid hormones directly regulate gene expression in the olfactory epithelium.
... In addition, several works have focused on how salmonids could use the polarization patterns of the sky for orientation (27). ...
With its never-ending blue color, the underwater environment often seems monotonic and featureless. However, to an animal with polarization-sensitive vision, it is anything but bland. The rich repertoire of underwater polarization patterns—a consequence of light’s air-to-water transmission and in-water scattering—can be exploited both as a compass and for geolocalization purposes. We demonstrate that, by using a bioinspired polarization-sensitive imager, we can determine the geolocation of an observer based on radial underwater polarization patterns. Our experimental data, recorded at various locations around the world, at different depths and times of day, indicate that the average accuracy of our geolocalization is 61 km, or 6 m of error for every 1 km traveled. This proof-of-concept study of our bioinspired technique opens new possibilities in long-distance underwater navigation and suggests additional mechanisms by which marine animals with polarization-sensitive vision might perform both local and long-distance navigation.
... Polarised light may also provide information about more broad-field environmental cues than those mentioned above. The best studied example is the incorporation of information from polarised skylight into the celestial compass of many insect species (reviews: Wehner 2001; Horváth and Varjú 2004;Horváth et al. 2014), a capacity that has also been suggested in some crustacean (Bainbridge and Waterman 1957) and mollusc species (Jander et al. 1963), and even some vertebrates (Taylor and Adler 1973;Able and Able 1993;Parkyn et al. 2003). Since the pattern of polarised skylight indicates the sun's compass bearing (the solar azimuth), it may be used as a reference frame for geographic body-axis orientation when the sun is not visible. ...
In recent years, the study of polarisation vision in animals has seen numerous breakthroughs, not just in terms of what is known about the function of this sensory ability, but also in the experimental methods by which polarisation can be controlled, presented and measured. Once thought to be limited to only a few animal species, polarisation sensitivity is now known to be widespread across many taxonomic groups, and advances in experimental techniques are, in part, responsible for these discoveries. Nevertheless, its study remains challenging, perhaps because of our own poor sensitivity to the polarisation of light, but equally as a result of the slow spread of new practices and methodological innovations within the field. In this review, we introduce the most important steps in designing and calibrating polarised stimuli, within the broader context of areas of current research and the applications of new techniques to key questions. Our aim is to provide a constructive guide to help researchers, particularly those with no background in the physics of polarisation, to design robust experiments that are free from confounding factors.
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... aspects, such as the structure of the sense organs, locomotion, and social behavior. Various methods of eliciting fish movement have been explored, including the use of sound, light, electrical/chemical stimuli, and water flow (Popper et al. 1998, Popper et al. 2004, Parkyn et al. 2003, Hodgson et al. 1971, Gardiner et al. 2007, Gardiner et al. 2010, Liao et al. 2006, Engelmann et al. 2000. Mechanosensory hair cells on the lateral line sensory organs allow fish to detect hydrodynamic pressure differences created by flow velocity gradients (Coombs et al. 1989, Dijkgraaf et al. 1963. ...
Fishes detect various sensory stimuli, which may be used to direct their behavior. Especially, the visual and water flow detection information are critical for locating prey, predators, and school formation. In this study, we examined the specific role of these two different type of stimulation (vision and vibration) during the obstacle avoidance behavior of carp, Cyprinus carpio. When a visual obstacle was presented, the carp efficiently turned and swam away in the opposite direction. In contrast, vibration stimulation of the left or right side with a vibrator did not induce strong turning behavior. The vibrator only regulated the direction of turning when presented in combination with the visual obstacle. Our results provide first evidence on the innate capacity that dynamically coordinates visual and vibration signals in fish and give insights on the novel modulation method of fish behavior without training.
... 33,34). Despite differences in mechanisms, there is ample behavioral evidence from behavioral and physiological training experiments (28,(35)(36)(37)(38)(39)(40), as well as direct cellular recordings in the retina (41,42), optic nerve (29,41,42), and optic tectum (43,44), that many nonmammalian vertebrates, particularly fish, have polarization sensitivity. However, there have been no studies to date of vertebrates relying on polarization cues to communicate. ...
Significance
Polarization, the alignment of light waves in a plane, is a property that many nonhuman animals can detect. Polarized body patterning on some animals has prompted research into polarization as a signaling modality, but experimental evidence is lacking. We found evidence for sexual selection on polarization ornamentation in a swordtail fish: sexually dimorphic polarization patterning with higher polarization contrast in males and females exhibiting a mate preference for this ornamentation. We manipulated male polarization properties in a mate choice experiment and found that females prefer males with polarized over depolarized ornamentation and that males may increase polarization contrast in social environments. Polarization signaling may provide enhanced display detection, along with privatized communication, due to the directional component of polarized light.
... Other sensory mechanisms and cues implicated in the migratory behaviour of fish include audition, chemotaxis, electrolocation, magnetic sense, rheotaxis, thermal gradients and vision (Parkyn et al., 2003). Although many sensory modalities may be needed to explain migration path selection at all scales, inclusion of only hydrodynamically based stimuli in the present form of the hypothesis is a reasonable first approximation for application at dams where high-energy flow fields frequently override or supersede emigrant responses to other stimuli (Popper and Carlson, 1998). ...
Understanding hydrodynamic cues used by outmigrating juvenile salmon (emigrants) to guide fine-scale swim path selection is critical to successful fish guidance and passage at man-made structures. We show how these cues can be inferred from channel features and complex flow fields of natural rivers through which emigrants pass. We then describe a new cue, ‘total hydraulic strain’, integrating properties of flow acceleration and turbulence through the spatial gradients in velocity to create a single flow field distortion metric amenable to the analysis of fish movement at the scale of large man-made structures. We explain how total hydraulic strain, together with the magnitude of velocity, provide sufficient information for any fish to distinguish between the two categories of channel features with their mechanosensory system. We demonstrate that total hydraulic strain, velocity magnitude and hydrostatic pressure can be integrated into rule-sets (the Strain–Velocity–Pressure (SVP) Hypothesis) to explain emigrant swim path selection near dams. To confirm the reasonableness of the SVP Hypothesis, we describe how its separate elements can be detected by different components of the fish mechanosensory system. We evaluate the SVP Hypothesis by (1) using it to explain the traces made by acoustically tagged emigrants overlaid on coincident total hydraulic strain and velocity magnitude fields, (2) using it to explain different passage efficiencies of competing bypass designs and (3) testing it via stepwise discriminant analysis to infer the relationship between hydrodynamic pattern and emigrant orientation. We conclude the SVP Hypothesis is a reasonable and useful approximation of the strategy used by emigrants to select their swim path through complex flow fields sufficient to serve as the basis of guidance and bypass system design.
... Whilst the mechanisms that bats might use to navigate are relatively unknown, some of the mechanisms that birds possess are also found to be used by many diverse animal taxa. Map and compass orientation is known in reptiles (Lohmann and Lohmann 1996), amphibians (Phillips 1996) and fish (Parkyn et al. 2003). Compass orientation is prevalent amongst arthropods (Wehner 1998). ...
Bats have been extensively studied with regard to their ability to orient, navigate and hunt prey by means of echolocation,
but almost nothing is known about how they orient and navigate in situations such as migration and homing outside the range
of their echolocation system. As volant animals, bats face many of the same problems and challenges as birds. Migrating bats
must relocate summer and winter home ranges over distances as far as 2,000km. Foraging bats must be able to relocate their
home roost if they range beyond a familiar area, and indeed circumstantial evidence suggests that these animals can home from
more than 600km. However, an extensive research program on homing and navigation in bats halted in the early 1970s. The field
of bird navigation has advanced greatly since that time and many of the mechanisms that birds are known to use for navigation
were not known or widely accepted at this time. In this paper I discuss what is known about orientation and navigation in
bats and use bird navigation as a model for future research in bat navigation. Technology is advancing such that previous
difficulties in studying orientation in bats in the field can be overcome and so that the mechanisms of navigation in this
highly mobile animal can finally be elucidated.
... Though these techniques have typically been restricted to domesticated birds, they may be applicable to C. alta (the predator), as various fish species have been shown to respond well to operant conditioning (e.g. Thompson, 1966; Gee et al., 1994; Sevenster et al., 1995; Parkyn et al., 2003). Numerous studies have also successfully employed video equipment as stimuli for fish behaviour studies (reviewed in Rowland, 1999; see also Kunzler and Bakker, 2001; Morris et al., 2003). ...
One of the key challenges of both ecology and evolutionary biology is to understand the mechanisms that maintain diversity. Negative frequency-dependent selection is a powerful mechanism for maintaining variation in the population as well as species diversity in the community. There are a number of studies showing that this type of selection, where individuals of a rare type (i.e. a rare morph or a rare species) experience higher survival than those of more common type(s). However, it is still not clear how frequency-dependent selection operates. Search image formation has been invoked as a possible, proximate explanation. Although the conceptual link between search image and frequency-dependent predation is often assumed in ecological and evolutionary studies, a review of the literature reveals a paucity of evidence demonstrating the occurrence of both in a natural predator-prey system. Advances in the field of psychology strongly support the existence of search image, yet these findings are not fully recognized in the realm of ecology and evolutionary biology, in part, we feel because of confusion and inconsistencies in terminology. Here we try to simplify the language, clarify the advances in the study of frequency-dependent predation and search image, and suggest avenues for future research. We feel that the investigations of both proximate (perceptual mechanisms) and ultimate (pattern of predation) processes are necessary to fully understand the importance of individual behavioural processes for mediating evolutionary and ecological diversity.
... Hence, it would be beneWcial to learn and memorize diVerent types of information and to orient according to the cues available under the speciWc environmental conditions. Many species of crustacean, Wsh, and sea turtles can rely on a large variety of spatial information to orient such as geomagnetic Weld, celestial and polarized light cues, ocean currents, olfactory, and other visual cues (Healy 1998;Odling-Smee and Braithwaite 2003;Parkyn et al. 2003;Horvath and Varju 2004;Lohmann et al. 2008;Shettleworth 2010). However, far fewer studies have investigated how diVerent kinds of spatial information interact in a controlled spatial task. ...
Cuttlefish are sensitive to linear polarization of light, a sensitivity that they use in predation and possibly in intraspecific communication. It has also been shown that cuttlefish are able to solve a maze using visual landmarks. In this study, cuttlefish were trained to solve a Y-maze with the e-vector of a polarized light and landmarks as redundant spatial information. The results showed that cuttlefish can use the e-vector orientation and landmarks in parallel to orient and that they are able to use either type of cue when the other one is missing. When they faced conflicting spatial information in the experimental apparatus, the majority of cuttlefish followed the e-vector rather than landmarks. Differences in response latencies in the different conditions of testing (training with both types of cue, tests with single cue or with conflicting information) were observed and discussed in terms of decision making. The ability to use near field and far field information may enable animals to interpret the partially occluded underwater light field.
... Fish use several cues for orientation during migration, e.g. olfactory cue (coho salmon O. kisutch, Nevitt et al. 1994; Wve-lined cardinalWsh C. quinquelineatus, Døving et al. 2006), the earth's magnetic Weld (blue shark Prionace glauca; stingray Urolophus halleri, Kalmijn 2000), and polarized light stimulus (juvenile rainbow trout Oncorhynchus mykiss, Parkyn et al. 2003). A magnetic cue is useful for long-distance cruising during ocean migration, while olfactory and visual cues provide migrators spatial information on local environments. ...
The ability to orient and navigate within a certain environment is essential for all animals, and spatial memory enables animals to remember the locations of such markers as predators, home, and food. Here we report that the migratory marine cardinalfish Apogon notatus has the potential to retain long-term spatial memory comparable to that of other animals. Female A. notatus establish a small territory on a shallow boulder bottom to pair and spawn with males. We carried out field research in two consecutive breeding seasons on territory settlement by individually marked females. Females maintained a territory at the same site throughout one breeding season. After overwintering in deep water, many of them (82.1%) returned to their breeding ground next spring and most occupied the same site as in the previous season, with only a 0.56 m shift on average. Our results suggest that female A. notatus have long-distance homing ability to pinpoint the exact location of their previous territory, and retain spatial memory for as long as 6 months.
... Twochannel PS systems enable more complex behaviors mediated by polarization vision. For instance, salmonids (Hawryshyn et al. 1990;Parkyn et al. 2003), like many insects and a wide range of other invertebrates (Wehner 2001), use celestial polarized light cues as a navigational mechanism. Furthermore, evidence from cephalopods suggests that polarization vision functions such as detection of transparent or reflective prey (Shashar et al. 1998(Shashar et al. , 2000 as well as a communication channel for interspecific and intraspecific interactions . ...
Using electroretinogram recording and microspectrophotometry we investigated spectral sensitivity and ultraviolet polarization sensitivity in three species of coral reef fishes commonly known as damselfishes. Here we show that three species of damselfishes (three-spot damselfish, Dascyllus trimaculatus; blacktail damselfish, D. melanurus; and blue-green chromis, Chromis viridis) have four classes of cone photoreceptors (lambda(max) ranges: ultraviolet 357-367 nm; short wavelength-sensitive 469-478 nm; medium wavelength-sensitive 482-493 nm; long wavelength-sensitive 512-524 nm; rods 499-500 nm). The three species shared similar combined spectral sensitivity but surprisingly complicated and varied polarization sensitivity. Damselfish examined in this study have three and four channel polarization sensitivity, the most complex polarization sensitivity recorded for any vertebrate. Such capacity could play an important role in mediating a conspecific visual communication network utilizing polarized light signals in the coral reef environment.
... Stomatopods, with the complex spectral and polarization sensitivity visual systems, have 4 prime axes for sensing polarization that may enable even finer discrimination ability (Marshall, Land, King, & Cronin, 1991;Marshall, Land, & Cronin, 1994) though so far only discrimination between orthogonal e-vectors within a single target has been demonstrated (Marshall, Cronin, Shashar, & Land, 1999). Rainbow trout, which possess a two-channel (horizontal vs. vertical) polarization sensitivity system (Hawryshyn, Arnold, Bowering, & Cole, 1990;Parkyn, Austin, & Hawryshyn, 2003), were shown to discriminate between two linearly polarized light patches only when the e-vector orientation differed by more than 45° (Degner & Hawryshyn, 2001). This low level of discrimination capability is expected to be insufficient for mediating contrast enhancement of objects. ...
Transparency is commonly used by zooplankton for camouflage in open waters. Polarization vision allows planktivorous animals to increase their prey's detectability. Polarization properties of zooplankton were analyzed by measuring changes in the transmitted light. The transmitted light was subjected to depolarization and phase retardance, resulting in a species-specific polarization contrast between animal and background; from 5% in Corycaeus sp. to 92% in Undinula vulgaris (Copepoda). This contrast diminishes exponentially with distance, reaching 50% of the inherent value at 1 and 2m, for moderately turbid and clear waters, respectively. However, at reactive distances of planktivorous fishes this contrast is reduced by less than 20%.
Since the first edition of this book, our understanding of vertebrate polarisation vision has increased significantly. Much of this work has concentrated on a number of species of fish, and the aim of this updated chapter is to highlight some of the new discoveries and new directions this area of animal polarisation vision has seen. Three distinctive research directions stand out and form the main sections of this chapter update: (1) mechanisms of polarisation sensitivity, (2) neural processing of polarisation information and (3) behavioural evidence of polarisation vision and associated visual ecology. The new additions to this chapter bring together work on molecular mechanisms of dichroism in cone photoreceptors and new evidence that questions the original measures of the levels of diffusion of the visual pigment in outer segment membranes. Advances in our understanding of how intra-retinal feedback influences the neural coding of polarisation information are also considered. Finally, several studies into the ability of fish to react to dynamic polarisation-based stimuli are also presented in conjunction with evidence that some fish also manipulate the degree of polarisation in the light that they reflect. However, it is still clear that this area of research lacks depth in much of the evidence, leaving many questions still wide open for future studies.
Although questions such as 'How do animals find their way, and how do they sense and process this information in the brain?' have been asked for centuries , the field of animal orientation and navigation has seen an immense leap forward in the past few decades. Moreover, our understanding has also expanded considerably regarding the molecular and physiological mechanisms of the different compasses and cues used by animals for orientation and navigation (Åkesson et al., Chapter 9, and Svensson et al., Chapter 11). Most notable are the advances made in our understanding of how animals can sense information provided by the geomagnetic field and use this information for behavioural tasks, for example for compass orientation during migration. But despite interdisciplinary and highly in-tegrative research over recent decades, we do not fully understand how animals perceive the Earth´s magnetic field. We know that animals use geomag-netic information for orientation tasks (see Åkesson et al., Chapter 9), but the receptor(s) remain to be identified. In this chapter, we review current knowledge in this area, outline challenges, and suggest future approaches to elucidate the sensory modalities used by animals for orientation and navigational tasks. 10.1 Magnetic sense Many hypotheses regarding how animals may sense the Earth's magnetic field have been proposed. Three principally different mechanisms to achieve this could theoretically be used to sense the strength of the Earth's magnetic field, including (1) induction , (2) magnetic particles, and (3) magnetically sensitive biochemical reactions. The latter two possibilities have emerged as the most promising candidate magnetoreceptor mechanisms: A light-dependent process is thought to detect the alignment of the geomagnetic field lines in space. This provides directional information that can be used for a magnetic compass (inclination compass, see Åkesson et al., Chapter 9). The other possibility is a detection process mediated by a ferromin-eral that reacts to very small changes in the direction and/or intensity of the magnetic field and, thereby, can be used as a magnetic compass and/or a magnetic positioning (map or signpost) sense (for reviews see Wiltschko and Wiltschko 1995a, 2005; Lohmann and Johnson 2000; Mouritsen and Ritz 2005). Both of the latter two mechanisms are supported by behav-ioural and physiological data in a broad range of organisms (see also Åkesson et al., Chapter 9). In some animals, like newts and birds, the presence of both mechanisms have independently been experimentally demonstrated to be present and used by the animals for different purposes, and thus are believed to be non-exclusive (Phil-lips 1986, Wiltschko and Wiltschko 1995b, and see 10.1.3). Here, we present the state-of-the-art knowledge of the sensory aspects of the two mag-netoreception mechanisms, and highlight recent advances and future challenges.
This book reviews all major models and hypotheses concerning the mechanisms supposed to underlie the process of navigation in vertebrates. It covers data on all major model groups of vertebrates studied in the context of animal navigation, such as migratory birds, homing pigeons, sea turtles, subterranean mammals and some migratory fish species. Some other - less studied - groups, e.g., whales, have also been touched. The first part of the book describes different sources of navigational information, with their specific navigational mechanisms known or supposed to be employed by animals for navigational goals. The second part discusses possible functions of these mechanisms in different vertebrates and in the context of different navigational tasks, ranging from short-range navigation, often performed by animals within as small an area as several square meters, to long-distance global-scale migrations performed by many birds and some sea turtles during their lifespan.
Abstract The underwater light field, which is nearly permanently and ubiquitously partially polarized, offers polarization sensitive animals special cues for mediatingva riousvisu alta sks. For the last fifty years, underwater polarization patterns have been studied with respect to their origin and their dependence on the optical properties of the medium, be it the atmosphere or the hydrosphere. Thisw as accomplished largely by in-situ measurements and ,analytical and numerical modeling of, underwater polarization patterns. The mechanisms involved in the sensitivity of Correspondence/Reprint request: Dr.N adav Shashar, The Inter UniversityInstitute for Marine Sciences in Eilat POBox 469,E ilat,88103, Israel. E -mail: nadavs@vms.huji.ac.il
Underwater, natural illumination typically varies strongly temporally and spatially. The reason is that waves on the water surface refract light into the water in a spatiotemporally varying manner. The resulting underwater illumination field forms a caustic network and is known as flicker. This work shows that caustics can be useful for stereoscopic vision, naturally leading to range mapping of the scene. Range triangulation by stereoscopic vision requires the determination of correspondence between image points in different viewpoints, which is often a difficult problem. We show that the spatiotemporal caustic pattern very effectively establishes stereo correspondences. Thus, we term the use of this effect as CauStereo. The temporal radiance variations due to flicker are unique to each object point, thus disambiguating the correspondence, with very simple calculations. Theoretical limitations of the method are analyzed using ray-tracing simulations. The method is demonstrated by underwater in situ experiments.
Polarized light (PL) sensitivity is relatively well studied in a large number of invertebrates and some fish species, but in most other vertebrate classes, including birds, the behavioural and physiological mechanism of PL sensitivity remains one of the big mysteries in sensory biology. Many organisms use the skylight polarization pattern as part of a sun compass for orientation, navigation and in spatial orientation tasks. In birds, the available evidence for an involvement of the skylight polarization pattern in sun-compass orientation is very weak. Instead, cue-conflict and cue-calibration experiments have shown that the skylight polarization pattern near the horizon at sunrise and sunset provides birds with a seasonally and latitudinally independent compass calibration reference. Despite convincing evidence that birds use PL cues for orientation, direct experimental evidence for PL sensitivity is still lacking. Avian double cones have been proposed as putative PL receptors, but detailed anatomical and physiological evidence will be needed to conclusively describe the avian PL receptor. Intriguing parallels between the functional and physiological properties of PL reception and light-dependent magnetoreception could point to a common receptor system.
Polarization may be sensed by imaging modules. This is done in various engineering systems as well as in biological systems, specifically by insects and some marine species. However, polarization per pixel is usually not the direct variable of interest. Rather, polarization-related data serve as a cue for recovering task-specific scene information. How should polarization-picture post-processing (P(4)) be done for the best scene understanding? Answering this question is not only helpful for advanced engineering (computer vision), but also to prompt hypotheses as to the processing occurring within biological systems. In various important cases, the answer is found by a principled expression of scene recovery as an inverse problem. Such an expression relies directly on a physics-based model of effects in the scene. The model includes analysis that depends on the different polarization components, thus facilitating the use of these components during the inversion, in a proper, even if non-trivial, manner. We describe several examples for this approach. These include automatic removal of path radiance in haze or underwater, overcoming partial semireflections and visual reverberations; three-dimensional recovery and distance-adaptive denoising. The resulting inversion algorithms rely on signal-processing methods, such as independent component analysis, deconvolution and optimization.
The effect of an induced salmonid parr-to-smolt metamorphosis ('smoltification') on the optical quality of the ocular lens was studied. In two separate experiments, rainbow trout (Oncorhynchus mykiss) parr were fed thyroxine in their diet to induce the metamorphosis. Lenses were excised at regular samplings during the treatment period and optically scanned using a custom scanning laser monitor. Radioimmunoassay was used to measure serum titers of thyroxine and 3,5,3'-triiodo-L: -thyronine. It was found that lens optical quality was consistently negatively correlated with 3,5,3'-triiodo-L: -thyronine levels, but not with thyroxine levels. To test if thyroid hormones are directly responsible for the change in optical quality, rainbow trout lenses were cultured for 72 h in a medium containing 3,5,3'-triiodo-L: -thyronine, but no effect was observed. The significance of these findings in the contexts of the fishes' visual capabilities and smolting physiology is discussed.
The retinas of many vertebrates have cone photoreceptors that express multiple visual pigments. In many of these animals, including humans, the original cones to appear in the retina (which express UV or blue opsin) may change opsin types, giving rise to new spectral phenotypes. Here we used microspectrophotometry and in situ hybridization with cDNA probes to study the distribution of UV and blue cones in the retinas of four species of Pacific salmon (coho, chum, chinook, and pink salmon), in the Atlantic salmon, and in the rainbow/steelhead trout. In Pacific salmon and in the trout, all single cones express a UV opsin at hatching (lambda(max) of the visual pigment approximately 365 nm), and these cones later transform into blue cones by opsin changeover (lambda(max) of the blue visual pigment approximately 434 nm). Cones undergoing UV opsin downregulation exhibit either of two spectral absorbance profiles. The first is characterized by UV and blue absorbance peaks, with blue absorbance dominating the base of the outer segment. The second shows UV absorbance diminishing from the outer segment tip to the base, with no sign of blue absorbance. The first absorbance profile indicates a transformation from UV to blue phenotype by opsin changeover, while the second type suggests that the cone is undergoing apoptosis. These two events (transformation and loss of corner cones) are closely associated in time and progress from ventral to dorsal retina. Each double cone member contains green (lambda(max) approximately 510 nm) or red (lambda(max) approximately 565 nm) visual pigment (double cones are green/red pairs), and, like the rods (lambda(max) approximately 508 nm), do not exhibit opsin changeover. Unlike Pacific salmonids, the Atlantic salmon shows a mixture of UV and blue cones and a partial loss of corner cones at hatching. This study establishes the UV-to-blue cone transformation as a general feature of retinal growth in Pacific salmonids (genus Oncorhynchus).
1. Visual orientation of the surface-living hemirhamphid teleost Zenarchopterus has been studied with individual fish swimming in an experimental vessel open to the air. Measurements of spontaneous heading preferences were made in the afternoon and morning respectively of two successive days, during which the sun's bearing differed by nearly 180°. Fish were tested under natural illumination of sun and sky as well as with six different e-vector directions of imposed linearly polarized light.2. Data were selected among other things on the criterion that maintenance of a given azimuth direction ± 20° for a 10 sec period counted as an oriented response. Comparison with the distributions of the total measurements justifies this selection.3. Zenarchopterus avoided the azimuth quadrant towards the sun. This suggests negative phototaxis but other explanations are possible.4. A strong southerly heading preference occurred on both days under natural illumination by sun and sky. The same marked preference is also ev...
Adult rainbow and purple parrot fishes (Scarus guacamaia and S. coelestius) on the south shore of Bermuda live in offshore caves at night. During the day they feed along the shoreline. These fish, caught over the feeding grounds, when released in areas apparently unfamiliar to them, move in a southeasterly direction (90° to 180° of north) regardless of underwater topographic or hydrographic features. This is the direction from their feeding grounds to their offshore caves. Circling, stopping and a lack of definite direction characterized the courses of fish released with cloud cover, at night, and with opaque eyecups. When a cumulus cloud partially obliterated the sun, fish swimming in a south-easterly direction either started to circle and/or stopped. After the cloud had passed by, the fish again swam in a southeasterly direction.
Orientation responses of juvenile rainbow trout (Oncorhynchus mykiss) to two linearly polarized light patches were examined under controlled laboratory conditions. Fish were trained to swim the length of the training tank under a polarized light field created by two linearly polarized stimuli that were oriented either parallel or perpendicular to the length of the tank. Trained fish were released in a circular tank and their angular responses were recorded. For each testing paradigm, the E-vector (electric vector) orientation of one of the two linearly polarized light patches was varied by 15 degrees between 0 degrees and 90 degrees. Each fish was therefore tested in seven different paradigms in which the two E-vector orientations differed by 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees. Rainbow trout oriented in a bimodal distribution when the two E-vector orientations differed by 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 90 degrees. These results suggest that rainbow trout perceived the two stimuli as being the same when the two E-vector orientations differed by 45 degrees or less. Conversely, rainbow trout did not significantly orient when the two E-vector orientations differed by 60 degrees and 75 degrees. Rainbow trout may be able to discriminate two E-vector orientations that differ between 60 degrees and 75 degrees, and therefore they do not significantly orient, since they perceive two distinct E-vectors to orient to instead of one. When rainbow trout were exposed to a depolarized light field, they did not exhibit significant orientation subsequent to the E-vector cue.
Summary Patterns of polarized light present in the clear dusk sky provide directional information relevant to the orientation behaviour of migratory birds. Experiments performed with white-throated sparrows (Zonotrichia albicollis) and American tree sparrows (Spizella arborea), North American night migrants, examined migratory orientation between the time of sunset and the first appearance of stars under several manipulations of skylight polarization patterns. Under clear skies, birds tested in Emlen funnel orientation cages oriented their hopping basically parallel to the E-vector of polarized light, with a bias towards the brightest part of the sky (sunset direction). Under solid, thick overcast conditions (no polarized light from the natural sky), birds showed axially bimodal hopping orientation parallel to an imposed E-vector. When birds were tested in cages covered with depolarizing material under a clear sky, their hopping orientation was seasonally appropriate and indistinguishable from controls viewing an unaltered clear sky. Skylight polarization patterns are not necessary for the occurrence of migratory orientation, but birds respond strongly to manipulations of the E-vector direction. The results reported here support the hypothesis that the relevant stimulus is the E-vector orientation rather than other parameters of skylight, e.g. intensity or colour patterns, degree of polarization. It appears that these night migrants are using skylight polarization at dusk as one of a set of multiple compass capabilities. Because of the necessarily artificial nature of the polarized light stimuli used in the experimental manipulations, it has not been possible to establish the relationship between this orientation cue and other known mechanisms (magnetic, sun and star compasses).
Orientation responses of juvenile rainbow trout (Oncorhynchus mykiss) to two linearly polarized light patches were examined under controlled laboratory conditions. Fish were trained to swim the length of the training tank under a polarized light field created by two linearly polarized stimuli that were oriented either parallel or perpendicular to the length of the tank. Trained fish were released in a circular tank and their angular responses were recorded. For each testing paradigm, the E-vector (electric vector) orientation of one of the two linearly polarized light patches was varied by 15° between 0° and 90°. Each fish was therefore tested in seven different paradigms in which the two E-vector orientations differed by 0°, 15°, 30°, 45°, 60°, 75°, and 90°. Rainbow trout oriented in a bimodal distribution when the two E-vector orientations differed by 0°, 15°, 30°, 45°, and 90°. These results suggest that rainbow trout perceived the two stimuli as being the same when the two E-vector orientations differed by 45° or less. Conversely, rainbow trout did not significantly orient when the two E-vector orientations differed by 60° and 75°. Rainbow trout may be able to discriminate two E-vector orientations that differ between 60° and 75°, and therefore they do not significantly orient, since they perceive two distinct E-vectors to orient to instead of one. When rainbow trout were exposed to a depolarized light field, they did not exhibit significant orientation subsequent to the E-vector cue.
The persistence of the embryonic (optic) fissure into adulthood and development of the falciform process in the eye varied among three fish species: Guppy Poecilia reticulata, Mozambique tilapia Tilapia mossambica, and brown trout Salmo trutta. The falciform process is a ridge of pigmented and vascular tissue associated with the embryonic fissure in teleosts. In guppies, the embryonic fissure closed during embryonic development, and no falciform process developed. In Mozambique tilapias, the embryonic fissure persisted into adulthood but was lined only with retinal pigment epithelium and lacked photoreceptive layers; it was associated with a partially formed falciform process. In brown trout, the embryonic fissure remained well defined with both retinal pigment epithelium and photoreceptor layers, and the falciform process was well developed. The temporal zone of the fissure in adult brown trout exhibited active growth and had a ventral area of high cone density. The well-developed fissure in brown trout and the oblique orientation of its ventrotemporal cones relative to incident light may be correlated with the species’ ability to locate prey above and in front of its body. This system also may allow brown trout to detect polarized light, which could assist in navigation during migration.
A system for the quantitative study of the learning capacity of rainbow trout and its application to the study of food preferences and of behaviour. Groups of trout were self-trained in about 10 days to actuate a trigger and feed themselves. This capacity was retained for 3 months without the stimulus of continuous reinforcement. Presented with a choice, conditioned populations showed a high degree of discriminatory ability towards a trigger that supplies food and one that does not. The choice system was used to examine preferences for the taste of pelleted foods. A trained population, under continuous illumination developed a feeding rhythm that occurred about every 8 h.
The demonstration of selective tidal stream transport in species as diverse as plaice, sole, cod, dogfish and eels suggests that the phenomenon may be of widespread significance in the migration of fishes on the European continental shelf. A computer simulation model has been written which interpolates the speed and direction of the tidal stream from the data given for the tidal diamonds on the appropriate British Admiralty Charts. The model allows for the cyclical change of current speed between neap and spring tides and includes three behavioural options for the fish: 1) semidiurnal vertical migration initiated at either slack water with a variable period of transport in midwater; 2) diurnal vertical migration with a variable ratio of time spent in midwater to time spent on the bottom; and 3) continuous transport (i.e. drift) in midwater. The aims of the model are to generate simulated tracks which: 1) taken individually, may lead to predictions about the behaviour of individual fish, which can be tested by further tracking experiments; and 2) taken collectively, may lead to predictions about the resulting distributions of whole populations, which can be tested by conventional tagging experiments. The first simulations have been concerned with the prespawning and postspawning migrations of plaice in the Southern Bight and English Channel and with the spawning migrations of silver European eels crossing the European shelf on their return to the Sargasso Sea. Some simulations have also been made of the tracks of plaice exhibiting diurnal vertical migrations on various feeding, spawning and staging grounds in the southern North Sea and English Channel.
If circular samples of equal size are reduced to their respective mean vectors, a sample of mean vectors is formed. This sample is referred to as a second-order sample. Kolmogorov’s test of goodness of fit may be used as a test for concentration. Since second-order samples are essentially bivariate, Hotelling’s T2 test (in case of normality) or a nonparametric competitor may be applied. Here a linear-circular correlation technique is recommended. Also studied is the comparison of two independent second-order samples.
The ability of teleosts to respond to the place of polarized light was determined by theri heart beat rate. When the plane of polarized light was changed, apparent cardiac deceleration was observed in tilapia, rainbow trout, and yellowtail, but there was no response in common carp and crimson sea-bream. To determine which organ perceives polarized light, the eye or the pineal organ, one or both were covered in some tests on tilapia and rainbow trout. The response disappeared when their eyes were covered. The fishes that respond posses polarized light vision, and polarized light is perceived by the eye.
Excerpt
I. THE PROBLEM
The ability to find compass directions with the help of the sun, and to keep the same compass direction despite the (apparent) movement of the sun during the day, has been known since 1950 [1, 2, 3]. During the last ten years this sun compass has been found to exist in many birds [3–7], several arthropods [8–14], in fishes [15, 16] of three families, and very recently in reptiles [17, 18]. In analyzing this behavior we encounter several interesting problems of modern biology. (Orientation, daily rhythm, seasonal periodicity, evolution.)
An essential prerequisite for this capacity is, besides sight of the sun, a clock furnishing the exact local time. Therefore, direction-finding has become a very useful method for studying this clock [19–25, 16]. Like the small hand of a mechanical clock, the compass animal changes its angle to the sun, or to an artificial light which it takes...
Adult sockeye salmon, Oncorhynchus nerka, return to the Fraser River via either of two routes: a northern route through Queen Charlotte Strait. Johnstone Strait, and the Strait of Georgia between the mainland and Vancouver Island, and a southern route along the west coast of Vancouver Island and through Juan de Fuca Strait. The proportions of the total run of sockeye salmon using the two routes varies substantially from year to year. Understanding the factors influencing the migratory routes of Fraser River sockeye salmon provides a basis for forecasting the coastal migrations of salmon as they make the transition between oceanic and riverine environments. Our analysis of west coast troll catch and high seas tag-recovery data indicates that the salmon make landfall in different coastal regions from year to year. If the majority of Fraser sockeye approach the coast of Vancouver Island, then most will migrate via the Strait of Juan de Fuca. However. when landfall occurs north of Vancouver Island in the Queen Charlotte Sound area. most homeward migrating Fraser sockeye will travel through Johnstone Strait. Northern diversion rates of Fraser River sockeye salmon for the period 1953-77 were positively correlated with Fraser River discharge. For the period 1978-85 a strong positive correlation was evident with sea surface temperature (SST) along the northwest coast of Vancouver Island (Kains Island lighthouse). We conclude that Fraser River discharge and SST in the vicinity of Kains Island do not guide sockeye salmon in any direct way during their coastal approach, but that they reflect oceanographic conditions that affect salmon migrations directly or indirectly by acting on the feeding distribution. distance. or direction they must travel to reach home. The Fraser River in British Columbia, Canada, is among the most important producers of sockeye salmon, Oncorhynchus nerka, in North America. Forty to sixty separate stocks, inhabiting the dif-ferent lakes of its watershed, produce 2 to 20 mil-lion adults yearly (IPSFC 1954-1985). Sockeye salmon from the Fraser River system generally spend 1 year in nursery lakes after emergence and then migrate to sea as smolts. Most spend two winters in the ocean, returning to spawn in their home river as 4-yr-olds. To reach the Fraser River from their ocean feeding grounds they can take either of two routes around Vancouver Island (Fig. 1). From 1953 until 1977, the majority homed via the southern route through the Strait of Juan de Fuca (average 84%, range 65-98%). Since 1978, a larger proportion of sockeye have migrated via the northern route through John-stone Strait (average through Juan de Fuca Strait 56%, range 20-78%) (IPSFC 1954-1986).
Eigenmannia, can shift its electric organ discharge (EOD) frequency in order to avoid jamming by signals originating from neighboring conspecifics. This jamming avoidance response (JAR) represents an ideal model system to study the neuronal implementation of behavior from the sensory periphery to the motor output. The neuronal mechanisms that guide this behavior on the sensory side clearly illustrate the processing of sensory information in separate but parallel channels, each specialized in computing different stimulus variables. Convergence at higher-order- level structures generates the emergence of pattern-specific neurons. It appears that also the motor side of the JAR is mediated by two separate pathways that function according to a push-pull principle. ·
The persistence of the embryonic (optic) fissure into adulthood and development of the falciform process in the eye varied among three fish species: guppy Poecilia reticulata, Mozambique tilapia Tilapia mossambica, and brown trout Salmo trutta. The falciform process is a ridge of pigmented and vascular tissue associated with the embryonic fissure in teleosts. In guppies, the embryonic fissure closed during embryonic development, and no falciform process developed. In Mozambique tilapias, the embryonic fissure persisted into adulthood but was lined only with retinal pigment epithelium and lacked photoreceptive layers; it was associated with a partially formed falciform process. In brown trout, the embryonic fissure remained well defined with both retinal pigment epithelium and photoreceptor layers, and the falciform process was well developed. The temporal zone of the fissure in adult brown trout exhibited active growth and had a ventral area of high cone density. The well-developed fissure in brown trout and the oblique orientation of its ventrotemporal cones relative to incident light may be correlated with the species' ability to locate prey above and in front of its body. This system also may allow brown trout to detect polarized light, which could assist in navigation during migration.
We review critically the Rayleigh test for uniformity as used by Curray. After discussing the test in Curray's form, we propose modifications: when the preferred orientation is known a priori, when the asymptotic formula must be corrected for small sample size, and when the natural range of angles is not 360° but 180°. When the preferred orientation is known, we use the statistic V', which is the component in the preferred direction of the vector sum used by Curray, and we discuss the circumstances under which a test based on V' may be regarded as unequivocally a best test for uniformity. We give formulas, a table, and charts for applying the Rayleigh test and the V-test to samples of all sizes that occur in practice. In an appendix we expose the relations between Rayleigh's test and a test proposed by Tukey.
The life cycle and homing migrations of salmon are defined within three distinct phases: (1) A sojourn in the inland stream beginning with the fertilized egg, through at least the larval and early fry stages, terminating with a short downstream migration of fry of pink or chum salmon or with a long downstream migration of smolts of sockeye, coho, Chinook, or Atlantic salmon to the sea, ( 2 ) a period of rapid growth and far ranging movement in the open sea, concluding at sexual maturity with an extensive homing migration of several hundred kilometers to the mouth of the home–river system, and ( 3 ) a strenuous upstream drive over barriers and waterfalls with rejection of tributary after tributary until the stream of origin is reached, where spawning takes place and the enervated salmon's lifecycle is ended. The fertilized eggs in the gravel-covered redds remain to perpetuate the cycle. This chapter focuses on the sensory mechanisms that the salmon possess and the environmental cues that they detect to find their way out of the river, around in the sea, and back to the river again with such remarkable accuracy. The chapter reviews and discusses some of the more credible theories that attempt to explain the salmon's return to its home river.
A connection between homing* behaviour and olfaction in fishes is now a well-established fact, but interpretations and concepts remain controversial. While speculations about a possible involvement of the olfactory sense with homing in fishes appeared at least a century ago (Buckland, 1880), direct scientific evidence for such a coupling has been obtained only during the course of the past four decades.
The locomotor orientation of eleven goldfish, 20–25 cm long, was monitored during periods varying between 24 hours and 8 1/2 days, to verify the response to a depolarized and polarized “sky”, 100 cm in diameter, and to abrupt 90 ° degree rotation of thee-vector. The monitor consisted of a cylindrical tank with 16 peripheral compartments (Fig. 1) to which the fish had free access. Entry into and exit from each compartment was electronically recorded. The distribution of entries, which had no cyclical relationship with the compartments in depolarized light, became significantly symmetrical and bimodal in polarized light with the “preferred” compartments oriented parallel with thee-vector. Abrupt 90 ° rotation of the vector counter clockwise maintained this relationship during the entire duration of the recordings (up to 17 hours) (Fig. 2). The mean of the orientation angles of the fish on leaving compartments aligned with thee-vector were significantly higher than those from the remaining compartments (Fig. 3). This behavior tended to keep the locomotor orientation parallel with thee-vector as the fish moved between compartments. A strong cyclical relationship between these orientation angles and the compartments of origin was present in polarized but absent in depolarized light. Counter clockwise 90 ° rotation of thee-vector maintained the cyclic behavior of angles but the relationship between the larger means and thee-vector shifted over one or two compartments. This shift disappeared in clockwise rotation. This phenomenon may be due to one of these directions being “unnatural”. The results demonstrate a pronounced sensitivity and response toe-vector orientation in the goldfish. The sensory mechanism remains unknown.
The evolution of elasmobranchs, which dates to at least Devonian time, reveals the early development of many of the characteristics present in living forms, including well-developed eyes. Although elasmobranchs occurred in both fresh and marine waters, modern species are common in most marine environments and rare in freshwater habitats. Consideration of visual adaptation in elasmobranchs, therefore, for the most part requires information of photic conditions in the sea. The classical studies of submarine light, e.g., attenuation due to scattering and absorption and its effect on the underwater spectrum, are reviewed. Most of these studies emphasize the static properties of underwater light and ignore changes in the time domain. They serve as a basis nevertheless to explain how the high absorption and the scattering of light by water molecules and included particles cause objects to become optically degraded over short distances. As a result, target detection is only useful over intermediate optical paths—meters rather than km. Elasmobranchs inhabit such different photic conditions that no single species can be considered representative. Thus, many forms possess a tapetum to enhance sensitivity at low light levels, while species living at depth have blue-shifted visual pigments. Most species, however, inhabit the upper photic regions of the sea where solar light during daylight is above photopic thresholds. Many of these species possess cones, presumably to enhance daytime vision. Consequently, emphasis is on light in the surface waters and the ecological problems of “seeing” targets in what is best described as a “dynamic light field”.
Salmonid fishes are famous for their tendency to home from feeding areas to spawn in their natal stream. In spite of considerable research effort, many aspects of homing are still poorly understood. This paper reviews four topics in the study of homing mechanisms which are presently unresolved or controversial. Pacific salmon (Oncorhynchus spp.) are emphasized but the issues apply widely within the family. The first topic is the migration from open ocean to coastal waters; tagging studies and correlations between ocean temperatures and migratory timing are in conflict regarding the possibility of true navigation by salmon. The second controversy involves homing through coastal waters and estuaries. These regions have physical characteristics which differ from both ocean and river environments and it is not clear how salmon make the transition from open water orientation to upstream migration. The third controversy concerns the process by which young salmon learn the chemical characteristics of their natal stream and the way in which adults use this information to return home. Specifically, do salmon imprint on the odors of their river only once, just prior to seaward migration, or sequentially during freshwater residence and migration? The fourth controversy concerns the role of species-specific and population- specific odors («pheromones») in homing. Salmon can distinguish between populations within their species and between full-sibling families within their population but the relevance of these olfactory responses to homing is not clear.
This study was concerned with the problem of how sockeye smolts (Oncorhynchus nerka) find their way out of lake systems during their migration from the nursery areas to the outlet. A general survey of the basic preferred directions and of the reference cues involved in direction finding is presented. /// Die vorliegende Arbeit behandelt die Frage, wie einjährige Sockeye-Lachse (Oncorhynchus nerka) ihren Weg von ihren Geburtsstätten zur Mündung des betreffenden Seensystems ins Meer finden. Es wird eine allgemeine Übersicht der bevorzugten Richtungen und der massgeblichen Richtmarken gegeben.
Hypopygus fires its electric organ in short pulses of less than 1 msec duration, at a variable rate between 60 and 100 Hz. While resting, the animal hovers near electrically detectable objects and follows their motions. This “electromotor” response is exploited to measure performance in electrolocation as a function of object size (Figs. 1, 2).Hypopygus pays particular attention to sensory feedback associated with its own discharges. It briefly raises its rate of discharge in response to sudden changes in feedback. Such changes, for example, are caused by extrinsic pulses which briefly precede or coincide with its own discharges (Figs. 3–5). In addition, electrolocation deteriorates when extrinsic pulses of sufficient intensity continually interfere with its own discharges in this manner, whereas non interfering pulses of comparable intensity have no adverse effect (Fig. 6). By modulating its frequency of discharge the animal avoids long sequences of coincidences between its discharges and trains of extrinsic pulses (Figs. 7,9). By only “listening” to sensations associated with its own discharges,Hypopygus appears to be able to electrolocate in the near presence of conspecifics. It remains unknown how the animal distinguishes feedback from its own discharges against sensations caused by extrinsic pulses.
The white bass, Roccus chrysops, has two principal spawning grounds 1.6 km apart on the northern shore of Lake Mendota. Fish displaced from these spawning grounds return faithfully to their respective spawning sites, and of 1366 fish marked and displaced to mid‐lake, a distance of 2.4 km, 181 were recaptured in fyke nets and less than 9% erred by being recaptured at the net on the other spawning ground. Fish released at the spawning ground were not recaptured in greater percentage than those displaced and released in mid‐lake.
Fish to which floats were attached for direct tracing moved generally north from the center of the lake when released on clear days. Moreover, fish released between the two spawning grounds also moved north on clear days. On cloudy days, however, or if blinded with eyecaps, they moved at random. Unexplained is how they differentiate between the two spawning areas; apparently it is by means other than with the aid of the sun.
A laboratory analysis of the sun‐compass mechanism was made. An immature specimen of Lepomis macrochirus was trained, at a specific time of day, to find cover in one of sixteen boxes of a circular tank. When trained, the fish entered the training box in a consistent compass‐direction at any time of day. Under an overcast sky the choices were completely unoriented. When tested under an artificial sun, (light bulb), this fish responded as though it were the real sun, at that time of day and sought cover in the “artificial” direction, reaffirming the presence of a biological clock. White bass were also successfully trained to a compass‐direction under the natural sun.
Lepomis gibbosus was tested with another method. It too has a sun‐compass mechanism.
These field and laboratory experiments suggest strongly that the sun serves as the point of reference, and that the animal compensates for its movement by a biological chronometer.
Adult sockeye salmon, Oncorhynchus nerka, return to the Fraser River via either of two routes: a northern route through Queen Charlotte Strait. Johnstone Strait, and the Strait of Georgia between the mainland and Vancouver Island, and a southern route along the west coast of Vancouver Island and through Juan de Fuca Strait. The proportions of the total run of sockeye salmon using the two routes varies substantially from year to year. Understanding the factors influencing the migratory routes of Fraser River sockeye salmon provides a basis for forecasting the coastal migrations of salmon as they make the transition between oceanic and riverine environments. Our analysis ofwest coast troll catch and high seas tag-recovery data indicates that the salmon make landfall in different coastal regions from year to year. If the majority ofFraser sockeye approach the coast of Vancouver Island, then most will migrate via the Strait ofJuan de Fuca. However. when landfall occurs north of Vancouver Island in the Queen Charlotte Sound area. most homeward migrating Fraser sockeye will travel through Johnstone Strait. Northern diversion rates ofFraser River sockeye salmon for the period 1953-77 were positively correlated with Fraser River discharge. For the period 1978-85 a strong positive correlation was evident with sea surface temperature (SST) along the northwest coast of Vancouver Island (Kains Island lighthouse). We conclude that Fraser River discharge and SST in the vicinity of Kains Island do not guide sockeye salmon in any direct way during their coastal approach, but that they reflect oceanographic conditions that affect salmon migrations directly or indirectly by acting on the feeding distribution. distance. or direction they must travel to reach home.
Food-conditioning experiments conducted in the laboratory demonstrated that groups of yearling sockeye salmon (Oncorhynchus nerka) can discriminate between vertical and horizontal planes of linearly polarized light. Removal of the adipose eyelid, a possible analyser of polarized light, did not abolish the response. The findings support the hypothesis that these fish can use polarization patterns for orientation during their seaward migration.
Sockeye salmon (Oncorhynchus nerka), pink salmon (O. gorbuscha), and chum salmon (O. keta) commonly return to their places of origin from distant high-seas areas. Maturing fish closely associated at high-seas localities travel in many different directions to their respective destinations. They also travel from many different high-seas localities to a common coastal area. Prior to their return to inshore waters, pink salmon perform ocean journeys which are associated with changes in temperature and which do not necessarily represent a direct approach to a spawning area. The ocean journeys of both juvenile and maturing salmon are largely independent of currents. Homing is not thought to be commonly accomplished by random or near-random ocean travel or by extensive searching of coastlines. It is suggested that ability to set a compass course, using a celestial feature, is insufficient to account for the indicated performance and that some form of bico-ordinate navigation may be required.
An examination of the modal salinity preferences of five Pacific salmon species showed the following pattern of temporal changes. The sequence began with a preference for fresh water, then changed gradually, in the direction of increasing seawater concentration. The terminal pattern indicated a preference for water of open ocean concentration. This temporal progression of salinity preference changes was shown to parallel closely the salinity gradients typical of river outflows through which young salmon pass on their way to the ocean. On the basis of this evidence the following orientation mechanism was proposed: that juvenile Pacific salmon are able to use estuarial salinity gradients as one of the directive cues in their seaward migration.
Silver salmon were captured in traps in Issaquah Creek and its East Fork. The olfactory pits of approximately one-half of the fish were occluded before all of them were displaced to the Issaquah about one mile below the junction of the two streams. The control salmon, unlike those with occluded olfactory pits, showed an excellent ability to repeat their original choice at the stream juncture. This is interpreted to mean that the operated fish were not able to differentiate between the two streams but were distributing themselves in a random fashion. The results, therefore, are in accord with those which would be expected if the fish were relying on their sense of smell in making this choice.
The literature on hearing in fish is reviewed. Experiments with Semotilus a. atromaculatus (Mitchill) showed perception over a range from 1 to 5,750 c.p.s. Fish from which the ears had been removed seemed to perceive frequencies from 20 to 200 c.p.s. Fish without the lateralis nerve behaved as normal fish. Normal fish could distinguish one-fifth of an octave in the range of 50 c.p.s. Trained on 50 c.p.s. they had absolute pitch for 70 c.p.s. A threshold curve over the range of 20 to 5,750 c.p.s. was established for this species.Highest sensitivity was at 280 c.p.s.; lowest at 20 c.p.s. and above 2,000 c.p.s. The movements of the fish in response to vibration stimuli were studied by means of motion pictures. The fish were able to locate the source of vibration, most likely oriented by fields of higher intensity in the experimental tank. In approaching the source the fish followed curved pathways. The relationships between length of pathway, direct distance from source of vibrations, and speed of locomotion were analysed. Measurements of sound intensity in the experimental rank indicated that intensity gradients existed along the pathways followed by the fish. Further measurements of low frequency vibrations in the water are in progress.
Behaviour patterns of juvenile sockeye salmon in fresh water are compared with those of chum and coho salmon. Both sockeye and chum fry are schooling fish, responding positively to currents and avoiding shallow waters. Of the two species, chums, however, form more active schools, travel more rapidly, have a less marked cover reaction and prefer stronger light and shallower water. Sockeye smolts, in contrast to coho smolts, are more active, show little thigmotactic and territorial behaviour and a more persistent response to current. The experimental findings are discussed in relation to the migratory behaviour of these fish. It is suggested that sockeye fry, emerging from cover as the light intensity falls are displaced downstream after dark. Moderate activity and a marked preference for deep water are mechanisms postulated for continued residence of sockeye fry in lakes. Further it is suggested that the smolt exodus is due to heightened general activity, both day and night, associated with strong response to current. This brings sockeye smolts into the outflow from the lake where they hold position during the day but are displaced down the river after dark. Coho smolts, responding less vigorously to currents and maintaining a measure of contact with specific objects in their environment, move seaward more slowly than sockeye.
Principles of Optics is one of the classic science books of the
twentieth century, and probably the most influential book in optics
published in the past forty years. This edition has been thoroughly
revised and updated, with new material covering the CAT scan,
interference with broad-band light and the so-called Rayleigh-Sommerfeld
diffraction theory. This edition also details scattering from
inhomogeneous media and presents an account of the principles of
diffraction tomography to which Emil Wolf has made a basic contribution.
Several new appendices are also included. This new edition will be
invaluable to advanced undergraduates, graduate students and researchers
working in most areas of optics.
Oriented responses to linearly polarized light have been quantitatively confirmed in the marine teleost Zenarchopterus studied in underwater field experiments with the aid of SCUBA. During six successive mornings 2485 heading measurements were made on 36 untrained fish. With natural illumination spontaneous azimuth orientation is mutiply dependent on the sun's bearing and apparently on the natural polarized light of blue sky or water as well as the direction of the interisland channel where the fish were collected. When a dichroic filter is placed over the fish polarotaxis is manifest as directional preferences mainly perpendicular and less strongly, parallel to the plane of polarization. This response is most intense when the imposed e-vector differs maximally (by 60°–90°) from that predominant in the natural illumination (90° to the sun's bearing). When the sun's disc is partly or wholly obscured by clouds polarotaxis is significantly weakened even though the polarization pattern visible to the fish through the dichroic filter would be virtually unchanged. More than moderate angular turning rates by the fish swimming in the experimental vessel also weaken their response to the e-vector. Individual fishes show different reactions: about one-third of those in full sunlight oriented strongly parallel and perpendicular to the imposed e-vector, another smaller group appears to orient obliquely to the polarization plane while the remainder respond weakly to the e-vector if at all. Continuing work is required to demonstrate the physiological mechanism and ecological significance of these behavioral patterns.
Two groups each of approximately 100 Moenkhausia dichroua, a schooling characid, showed a long–lasting, constant–oriented swimming when placed in a light–centred circular channel. This apparatus consists of a 1–m diameter circular channel illuminated by either a central or a peripheral light system, so that the light angle is constant all around the channel. With the central light at a fixed angle, fish swam for several months in one direction and reversed direction at a certain date. When the light angle was increased by 10° every other day between 0° (horizontal) and 90° (vertical), swimming direction was reversed at a particular angle in each experiment. This response to artificial light suggests that this small schooling fish uses the sun as an orientation clue in its seasonal migrations.
Of 12 homing pigeons tested, four could be trained to discriminate between a linearly polarized light source with a rotating axis of polarization and the same light source with a stationary axis of polarization. Initially, all 12 pigeons were trained to discriminate between rotating and nonrotating crosshairs. The crosshairs were gradually faded until only polarized light remained. The response was a classically conditioned increase in heart rate. An additional control series was performed using neutral density filters. This is the first evidence for polarized light detection in birds.