Figure - available from: Journal of Comparative Physiology A
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Schematic representations of the holding method for electrophysiological recording. a The animal cut the second abdominal segment was introduced into the plastic tube and the head was glued by beeswax and resin to separate electrically. b A part of the compound eye was pained and the tip of the electrode was placed just below the cornea at the centre of an unpainted area. (PA) preamplifier. c, d Sandhoppers with the dorsal 1/3 region or 2/3 ventral region of their eyes painted, respectively. e Transmittance curve of the Blue gelatine filter
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We investigated the eye regionalization in Talitrus saltator by morphological, electrophysiological and behavioural experiments. Each ommatidium possesses five radially arranged retinular cells producing a square fused rhabdom by R1–R4 cells; the smaller R5 exists between R1 and R4. The size of R5 rhabdomere is larger in the dorsal part and becomes...
Citations
... Although it is well established that skylight polarization is perceived and used as a celestial orientation factor by many crustaceans [6,8,9,21,22], T. saltator does not use of the e-vector to orient to the correct sea-land direction of the home beach [17,23]. On the other hand, the ability to perceive polarized light has been suggested in some supralittoral amphipods such as T. saltator and Platorchestia platensis [12,23,24], and it is notable also that T. saltator possesses an arrangement of the rhabdomeres that might enable e-vector interpretation and utilization [17,23,25]. Therefore, we carried out some behavioral tests aimed to clarify the role of the skylight polarization perception in the zonal recovery of T. saltator. ...
... The bowl was covered with an opaline Plexiglas dome (diameter = 30 cm, Fig. 1) to diffuse the incoming artificial light on the bowl and obscure any potential external visual cues. Since previous experiments showed that some celestial cues used in the orientation of this species are perceived in the UV -blue range [26] and three different peaks of ERG spectral sensitivity curves were observed at 390, 430, and 450 nm [24,25] we used a blue gelatin filter (no. 118 Light Blue, λmax = 450 nm). ...
... The comparison between the number of radially oriented individuals registered in previous releases made under natural sky with the sun screened out (data from [17,25]) and the number of radially oriented sandhoppers registered under the control condition of this study (125 out of 179 = 70%, G = 2.310, df = 1, P = NS, G tests) and the experimental one (155 out of 239 = 65%; G = 1.148, df = 1, P = NS, G test) does not reach statistical significance. ...
It is well known that the celestial polarization is used as a compass cue by many species of insects and crustaceans. Although it has been shown that the sandhopper Talitrus saltator perceives polarized light and possesses an arrangement of the rhabdomeres that could allow e-vector interpretation and utilization, T. saltator does not use the e-vector of the skylight polarization as a compass cue when making excursions along the sea–land axis of sandy shores. We performed tests in confined conditions to clarify if skylight polarization is somehow involved in the zonal recovery of T. saltator . We observed the directional responses of sandhoppers in a transparent bowl under an artificial sky (an opaline Plexiglas dome). The bowl was covered by a blue gelatin filter with a grey filter (control condition) and a linear polarizing filter (experimental conditions) positioned under the blue one in such a way as to occupy half of the upper surface of the Plexiglas bowl so as to create a linear polarization gradient. Our experiments confirm that T. saltator perceives polarized light and highlight that this visual capability determines the perception, or perhaps the increase, of the radiance and/or spectral gradient and their use as compass cues in the zonal orientation. Moreover, our findings confirm that the radiance gradient is used as a chronometric compass orienting reference in the absence of other celestial orienting cues.
... From seven to eight replicas were carried out for each treatment. The amount of paper -dry fish food and bioplastic sheets was established on the basis of previous studies on the same species, preventing them from running out of food (Ciofini et al., 2020). Before the beginning of the experiment, individuals were fasted for 2 days. ...
Talitrid amphipods are an important component of detritus web, playing a key role in the fragmentation of organic matters of marine and terrestrial origin, and it is well known that sandhoppers ingest microplastics. To assess the effective consumption of bioplastics and their effects on survival rate and on pollutants transfer (i.e. phthalates) on supralittoral arthropods, laboratory experiments were conducted by feeding adult T. saltator with two different types of bioplastic commonly used in the production of shopping bags. Groups of about 20 individuals were fed with 10 × 10 cm sample sheets of the two types of bioplastic for four weeks. The results show that amphipods ingest bioplastics even in the absence of microbial film and that ingestion of bioplastic can have effects on talitrid amphipods. Microtomographic analyses of faecal pellets seem consistent with this finding. The high phthalate concentrations in freshly collected individuals suggest the presence in the environment of these compounds, and the ability of amphipods to assimilate them, while the decrease in phthalate concentrations in bioplastic-fed individuals could be attributed to the scavenging effect of virgin plastic, as already observed in a previous study. In summary, the results indicate that different bioplastics may have effects on T. saltator (i.e. survival rate and faecal pellets structure) and confirm a potential role of amphipods in the degradation of bioplastics in supralittoral zone of marine sandy beaches, even when bioplastics are not colonized by bacterial biofilm that seems to improve palatability.
... responding to gradients of light intensity and polarisation. Behavioural experiments in other talitrid amphipods support this notion (Ercolini and Scapini 1976, Forward et al. 2009, Cohen et al. 2010, Ugolini et al. 2012, Cohen and Putts 2013, Ugolini 2014, Ciofini et al. 2020. Simple behavioural experiments in Parhyale suggest that they have a phototactic response (Ramos et al. 2019). ...
Arthropods are the most abundant and diverse animals on earth. Among them, pancrustaceans are an ancient and morphologically diverse group, comprising a wide range of aquatic and semi-aquatic crustaceans as well as the insects, which emerged from crustacean ancestors to colonise most terrestrial habitats. Within insects, Drosophila stands out as one of the most powerful animal models, making major contributions to our understanding of development, physiology and behaviour. Given these attributes, crustaceans provide a fertile ground for exploring biological diversity through comparative studies. However, beyond insects, few crustaceans are developed sufficiently as experimental models to enable such studies. The marine amphipod Parhyale hawaiensis is currently the best established crustacean system, offering year-round accessibility to developmental stages, transgenic tools, genomic resources, and established genetics and imaging approaches. The Parhyale research community is small but diverse, investigating the evolution of development, regeneration, aspects of sensory biology, chronobiology, bioprocessing and ecotoxicology.
... According to this hypothesis, we reasoned that the ability of T. saltator to detect light in the UV range may be ecologically advantageous in that it renders its overall compass system more reliable. However, T. saltator perceives UVblue wavelengths mainly with the lower part of the eye, while the upper part presents photopigments both for UV-blue and for green wavelengths (Ciofini et al., 2020). Therefore, we can imagine that the radiance and spectral gradients are perceived with the upper (dorsal) part of the eye while the UV-blue sensitivity of the lower part is more related to the identification of the sea hemicycle, given the importance of the perception of the coloured landscape (Ugolini et al., 2006), and not only of the contrast between the sea and land hemicycle in the zonal recovery of T. saltator. ...
The sandhopper Talitrus saltator relies on both the sun and the moon compasses to return to the belt of damp sand of the beach in which it lives buried during the day. In addition to the sun, the gradient of radiance and the spectral distribution across the sky could provide directional information that T. saltator can potentially use to orient itself during the day even when the sun is not visible (e.g. cloudy sky). The scope of this work was 1) to determine the intensity levels of sky radiance that the sandhoppers use in their zonal recovery and 2) to investigate whether this species relies on the celestial spectral gradient in its zonal recovery. Sandhoppers were tested in the laboratory under artificial radiance or spectral gradients.
Our results show that under an artificial sky, simulating the natural radiance gradient on a cloudless day, sandhoppers orientated toward the correct seaward direction of their home beach, however, individuals lost their ability to use the intensity gradient as an orientation cue when the radiance was attenuated by at least 40%. Sandhoppers were also able to head in the correct seaward direction of their home beach at any time of the day by using the spectral gradient as their only source of visual orientation reference.
Arthropods are the most abundant and diverse animals on earth. Among them, pancrustaceans are an ancient and morphologically diverse group, comprising a wide range of aquatic and semi-aquatic crustaceans as well as the insects, which emerged from crustacean ancestors to colonize most terrestrial habitats. Within insects, Drosophila stands out as one of the most powerful animal models, making major contributions to our understanding of development, physiology and behavior. Given these attributes, crustaceans provide a fertile ground for exploring biological diversity through comparative studies. However, beyond insects, few crustaceans are developed sufficiently as experimental models to enable such studies. The marine amphipod Parhyale hawaiensis is currently the best established crustacean system, offering year-round accessibility to developmental stages, transgenic tools, genomic resources, and established genetics and imaging approaches. The Parhyale research community is small but diverse, investigating the evolution of development, regeneration, aspects of sensory biology, chronobiology, bioprocessing and ecotoxicology.
