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Electron micrographs of nervous tissue in adipose fin. ( a ) Nerve (Ne) containing dense nuclei (N) of neurons and several myelinated (MA) and unmyelinated (UA) axons, are suspended from a collagen cable (CC). More than one ALC is connected to the nerve (arrows). Scale bar, 5 m m. ( b ) Cross section of a nerve with three myelinated axons (MA) and unmyelinated axons (UA), which are surrounded by processes of glial cells (GC). Scale bar, 1 m m. ( c ) Nerve containing UA and a GC. Scale bar, 0.5 m m. ( d ) Close up of ( b ) showing neurotubules in GC outside myelin sheath (My) of axon and neurofilaments (NF) inside axon. Scale bar, 0.2 m m.
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A wide variety of rudimentary and apparently non-functional traits have persisted over extended evolutionary time. Recent evidence has shown that some of these traits may be maintained as a result of developmental constraints or neutral energetic cost, but for others their true function was not recognized. The adipose fin is small, fleshy, non-raye...
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Context 1
... Our results show for the first time to our knowledge, unambiguous evidence of nervous tissue revealing a neural network throughout the fin which is consistent with a sensory function of the adipose fin. The adipose fin of juvenile brown trout ( S. trutta ) (figure 1 a,b ) comprises four main layers: epidermis, dermis, hypodermis and subdermal space. The first three of these are continuous with the layers of the integument of the trout (figure 1 c ). The combined epidermis and dermis taper in thickness from base to apex of the fin, measuring about 95 m m at the base and 65 m m at the apex (figure 1 c ). The subdermal space is a region of loose connective tissue bridged by roughly 2 m m thick collagen cables spanning the two sides of the fin (figure 1 d ). In the intervening space, one finds numerous astrocyte-like cells (ALCs), fibroblasts, a few small blood vessels (figure 1 d ), nerves and groups of collagen fibres often in bundles, but no adipose tissue. ( a ) Nervous tissue in the subdermal space TEM revealed several nerves in the subdermal space, often associated with the collagen cables that linked the two sides of the fin as well as ALCs (figure 2 a ). These nerves sometimes contained both myelinated and unmyelinated axons (figure 2 a,b ), or just unmyelinated ones (figure 2 c ), surrounded by neuroglial cells. Within the axons, we observed neurofibrils (about 12 nm diameter) and outside the axons, in the cytoplasm of a neuroglial supporting cell, there were many neurotubules (about 24 nm diameter; figure 2 d ). Serial 1 m m long sections of the fin stained with toluidine blue revealed in the subdermal space a network of ALCs in close association with nerves (figure 3 a,b ). At the caudal free edge of the fin, numerous rod-like actinotrichia were seen (figure 3 a ). Silver-stained tissue observed in the SEM with a back- scatter electron detector, revealed that both nerves and ALCs and their radiating processes were impregnated with silver but not some nearby fibroblasts and pigment cells. The network of ALCs was readily apparent, present- ing as bright cells against a dark background (figure 3 c ). Nerves were observed in both long and cross section, often more than one axon was visible and some with ALC processes connected to them (figure 3 d ). Prelimi- nary evidence obtained from adipose fins that had been stained with zn-12 antibody, revealed six to eight nerves entering the cut surface of the fin and anastomizing inside the fin to form a neural network (figure 3 e , micrograph courtesy of Dr Roger Croll, Dalhousie University). ( b ) Structure of ALCs and the subdermal space There was no adipose tissue inside the ‘adipose’ fin. A few lipid droplets were observed beneath the fin (figure 1 c ...
Context 2
... Our results show for the first time to our knowledge, unambiguous evidence of nervous tissue revealing a neural network throughout the fin which is consistent with a sensory function of the adipose fin. The adipose fin of juvenile brown trout ( S. trutta ) (figure 1 a,b ) comprises four main layers: epidermis, dermis, hypodermis and subdermal space. The first three of these are continuous with the layers of the integument of the trout (figure 1 c ). The combined epidermis and dermis taper in thickness from base to apex of the fin, measuring about 95 m m at the base and 65 m m at the apex (figure 1 c ). The subdermal space is a region of loose connective tissue bridged by roughly 2 m m thick collagen cables spanning the two sides of the fin (figure 1 d ). In the intervening space, one finds numerous astrocyte-like cells (ALCs), fibroblasts, a few small blood vessels (figure 1 d ), nerves and groups of collagen fibres often in bundles, but no adipose tissue. ( a ) Nervous tissue in the subdermal space TEM revealed several nerves in the subdermal space, often associated with the collagen cables that linked the two sides of the fin as well as ALCs (figure 2 a ). These nerves sometimes contained both myelinated and unmyelinated axons (figure 2 a,b ), or just unmyelinated ones (figure 2 c ), surrounded by neuroglial cells. Within the axons, we observed neurofibrils (about 12 nm diameter) and outside the axons, in the cytoplasm of a neuroglial supporting cell, there were many neurotubules (about 24 nm diameter; figure 2 d ). Serial 1 m m long sections of the fin stained with toluidine blue revealed in the subdermal space a network of ALCs in close association with nerves (figure 3 a,b ). At the caudal free edge of the fin, numerous rod-like actinotrichia were seen (figure 3 a ). Silver-stained tissue observed in the SEM with a back- scatter electron detector, revealed that both nerves and ALCs and their radiating processes were impregnated with silver but not some nearby fibroblasts and pigment cells. The network of ALCs was readily apparent, present- ing as bright cells against a dark background (figure 3 c ). Nerves were observed in both long and cross section, often more than one axon was visible and some with ALC processes connected to them (figure 3 d ). Prelimi- nary evidence obtained from adipose fins that had been stained with zn-12 antibody, revealed six to eight nerves entering the cut surface of the fin and anastomizing inside the fin to form a neural network (figure 3 e , micrograph courtesy of Dr Roger Croll, Dalhousie University). ( b ) Structure of ALCs and the subdermal space There was no adipose tissue inside the ‘adipose’ fin. A few lipid droplets were observed beneath the fin (figure 1 c ...
Context 3
... Our results show for the first time to our knowledge, unambiguous evidence of nervous tissue revealing a neural network throughout the fin which is consistent with a sensory function of the adipose fin. The adipose fin of juvenile brown trout ( S. trutta ) (figure 1 a,b ) comprises four main layers: epidermis, dermis, hypodermis and subdermal space. The first three of these are continuous with the layers of the integument of the trout (figure 1 c ). The combined epidermis and dermis taper in thickness from base to apex of the fin, measuring about 95 m m at the base and 65 m m at the apex (figure 1 c ). The subdermal space is a region of loose connective tissue bridged by roughly 2 m m thick collagen cables spanning the two sides of the fin (figure 1 d ). In the intervening space, one finds numerous astrocyte-like cells (ALCs), fibroblasts, a few small blood vessels (figure 1 d ), nerves and groups of collagen fibres often in bundles, but no adipose tissue. ( a ) Nervous tissue in the subdermal space TEM revealed several nerves in the subdermal space, often associated with the collagen cables that linked the two sides of the fin as well as ALCs (figure 2 a ). These nerves sometimes contained both myelinated and unmyelinated axons (figure 2 a,b ), or just unmyelinated ones (figure 2 c ), surrounded by neuroglial cells. Within the axons, we observed neurofibrils (about 12 nm diameter) and outside the axons, in the cytoplasm of a neuroglial supporting cell, there were many neurotubules (about 24 nm diameter; figure 2 d ). Serial 1 m m long sections of the fin stained with toluidine blue revealed in the subdermal space a network of ALCs in close association with nerves (figure 3 a,b ). At the caudal free edge of the fin, numerous rod-like actinotrichia were seen (figure 3 a ). Silver-stained tissue observed in the SEM with a back- scatter electron detector, revealed that both nerves and ALCs and their radiating processes were impregnated with silver but not some nearby fibroblasts and pigment cells. The network of ALCs was readily apparent, present- ing as bright cells against a dark background (figure 3 c ). Nerves were observed in both long and cross section, often more than one axon was visible and some with ALC processes connected to them (figure 3 d ). Prelimi- nary evidence obtained from adipose fins that had been stained with zn-12 antibody, revealed six to eight nerves entering the cut surface of the fin and anastomizing inside the fin to form a neural network (figure 3 e , micrograph courtesy of Dr Roger Croll, Dalhousie University). ( b ) Structure of ALCs and the subdermal space There was no adipose tissue inside the ‘adipose’ fin. A few lipid droplets were observed beneath the fin (figure 1 c ...
Context 4
... Our results show for the first time to our knowledge, unambiguous evidence of nervous tissue revealing a neural network throughout the fin which is consistent with a sensory function of the adipose fin. The adipose fin of juvenile brown trout ( S. trutta ) (figure 1 a,b ) comprises four main layers: epidermis, dermis, hypodermis and subdermal space. The first three of these are continuous with the layers of the integument of the trout (figure 1 c ). The combined epidermis and dermis taper in thickness from base to apex of the fin, measuring about 95 m m at the base and 65 m m at the apex (figure 1 c ). The subdermal space is a region of loose connective tissue bridged by roughly 2 m m thick collagen cables spanning the two sides of the fin (figure 1 d ). In the intervening space, one finds numerous astrocyte-like cells (ALCs), fibroblasts, a few small blood vessels (figure 1 d ), nerves and groups of collagen fibres often in bundles, but no adipose tissue. ( a ) Nervous tissue in the subdermal space TEM revealed several nerves in the subdermal space, often associated with the collagen cables that linked the two sides of the fin as well as ALCs (figure 2 a ). These nerves sometimes contained both myelinated and unmyelinated axons (figure 2 a,b ), or just unmyelinated ones (figure 2 c ), surrounded by neuroglial cells. Within the axons, we observed neurofibrils (about 12 nm diameter) and outside the axons, in the cytoplasm of a neuroglial supporting cell, there were many neurotubules (about 24 nm diameter; figure 2 d ). Serial 1 m m long sections of the fin stained with toluidine blue revealed in the subdermal space a network of ALCs in close association with nerves (figure 3 a,b ). At the caudal free edge of the fin, numerous rod-like actinotrichia were seen (figure 3 a ). Silver-stained tissue observed in the SEM with a back- scatter electron detector, revealed that both nerves and ALCs and their radiating processes were impregnated with silver but not some nearby fibroblasts and pigment cells. The network of ALCs was readily apparent, present- ing as bright cells against a dark background (figure 3 c ). Nerves were observed in both long and cross section, often more than one axon was visible and some with ALC processes connected to them (figure 3 d ). Prelimi- nary evidence obtained from adipose fins that had been stained with zn-12 antibody, revealed six to eight nerves entering the cut surface of the fin and anastomizing inside the fin to form a neural network (figure 3 e , micrograph courtesy of Dr Roger Croll, Dalhousie University). ( b ) Structure of ALCs and the subdermal space There was no adipose tissue inside the ‘adipose’ fin. A few lipid droplets were observed beneath the fin (figure 1 c ...
Citations
... Mass marking of salmon by fin clipping (i.e., the partial or full removal of a fish's fins) is a procedure commonly used in intensive aquaculture and hatcheries to distinguish farmed or hatchery-reared salmon from wild salmon (Uglem et al., 2020). Similarly, to tail docking and beak trimming, fin clipping may cause pain and injury in fish and alter swimming efficiency (Roques et al., 2010;Buckland-Nicks et al., 2021;Schroeder & Sneddon, 2017;Thomson et al., 2020;Uglem et al., 2020). Production system managers argue that fin clipping is the easiest method to identify fish because it is inexpensive, quick, and requires minimal equipment and training (Hammer and Lee Blankenship, 2001). ...
The number of animals bred, raised, and slaughtered each year is on the rise, resulting in increasing impacts to welfare. Farmed animals are also becoming more diverse, ranging from pigs to bees. The diversity and number of species farmed invite questions about how best to allocate currently limited resources towards safeguarding and improving welfare. This is of the utmost concern to animal welfare funders and effective altruism advocates, who are responsible for targeting the areas most likely to cause harm. For example, is tail docking worse for pigs than beak trimming is for chickens in terms of their pain, suffering, and general experience? Or are the welfare impacts equal? Answering these questions requires making an interspecies welfare comparison; a judgment about how good or bad different species fare relative to one another. Here, we outline and discuss an empirical methodology that aims to improve our ability to make interspecies welfare comparisons by investigating welfare range, which refers to how good or bad animals can fare. Beginning with a theory of welfare, we operationalize that theory by identifying metrics that are defensible proxies for measuring welfare, including cognitive, affective, behavioral, and neuro-biological measures. Differential weights are assigned to those proxies that reflect their evidential value for the determinants of welfare, such as the Delphi structured deliberation method with a panel of experts. The evidence should then be reviewed and its quality scored to ascertain whether particular taxa may possess the proxies in question to construct a taxon-level welfare range profile. Finally, using a Monte Carlo simulation, an overall estimate of comparative welfare range relative to a hypothetical index species can be generated. Interspecies welfare comparisons will help facilitate empirically informed decision-making to streamline the allocation of resources and ultimately better prioritize and improve animal welfare.
... Adipose fins of teleosts were for a long time considered to be vestigial and lacking innervation or obvious function (Garstang, 1931). A series of papers on adipose fins of salmonids (Buckland-Nicks, 2016;Buckland-Nicks et al., 2011;Reimchen & Temple 2004) and catfish (Stewart & Hale, 2015) have recently proven this theory to be incorrect. Rather, the adipose fin, although varied in origin (Stewart et al., 2014), is a highly innervated structure (Buckland-Nicks, 2016;Koll et al., 2020) that can act as a sensitive mechanosensory organ for monitoring precaudal flow (Aiello et al., 2016;Koll et al., 2020). ...
... Nonetheless, the structure and innervation of adipose fins is achieved in different ways in these two groups. Salmonid adipose fins are flexible, lack muscles, fin rays or adipose tissue but have an extensive neural network interconnected with astrocyte-like glial cells linked to a collagen framework (Buckland-Nicks, 2016;Buckland-Nicks et al., 2011;Koll et al., 2020); whereas the catfish adipose lacks the glial cell network and relies more on information conveyed by the deformation of afferent nerves and their fine branches (Aiello et al., 2016). These proprioceptive adipose fins are passive, as they do not have any muscles or endoskeleton and their mobility is based on water motion. ...
... Muscle fibres (M) attached to cartilage. Scale bar = 250 μassumptions have since been shown to be incorrect, as detailed studies have shown that adipose fins can have hydrodynamic benefits(Reimchen & Temple, 2004), be highly innervated(Buckland-Nicks, 2016;Buckland-Nicks et al., 2011;Stewart & Hale, 2013) and be capable of sensitive mechanosensory responses to stimuli(Aiello et al., 2016;Koll et al., 2020). ...
Adipose fins of teleost fishes have been shown to function as mechanosensory organs that respond to minute bending forces created by turbulence in fast‐flowing streams. Nonetheless, adipose fins also exist in some fishes that occupy still waters, including lanternfish (Myctophidae) in the deep sea. The authors examined adipose fin structure in northern lampfish, Stenobrachius leucopsarus, from coastal British Columbia. After fixation, embedding and sectioning of the adipose and supporting tissue, it was evident that lanternfish adipose fins are stiffened by compound actinotrichia, acting like fin rays, that would create a higher aspect ratio. The actinotrichia converge at the base of the fin in a hinge point complex that anteriorly interacts with a cartilaginous endoskeletal rod, controlled by skeletal muscles. Afferent nerves enter the fin at this point and form fine branches as they track deeper alongside actinotrichia. The authors propose that the vertical nightly migration to surface waters, as well as predator evasion within large schools, results in microturbulence. In these circumstances, the adipose fin acts as a mechanosensor providing feedback to the caudal fin, as it occurs in salmonids and catfish.
... Transfer of PCBs into blood circulation in fasting Northern elephant seals has been reported by assessing blubber (fat reserves) and serum (lipid fraction) (Debier et al., 2006). A study of the ultrastructure of salmonid adipose fin reported on the presence of blood vessels in the subdermal space (inner layer) of the adipose fins of brown trout (Salmo trutta) (Buckland-Nicks et al., 2012). Only two samples of Atlantic salmon had detectable concentrations of PCBs (#153 and #138). ...
We report on concentrations of polybrominated diphenylethers (PBDEs), polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p′-DDE) and hexachlorobenzene (HCB) measured in the adipose fins of returning adult Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) to the river Tees in the Northeast of England. Overall, higher concentrations of these contaminants were found in sea trout samples, where detected congeners reflected the more widely used commercial formulations, in particular for the PBDEs. Our results suggest that these fish could be bioaccumulating persistent organic pollutants via diet during their migratory routes (North Sea and the Norwegian Sea) and, in addition, some level of re-mobilisation of these compounds could still be occurring in the UK eastern coastal areas. The use of adipose fin of returning salmonids could be further developed as a non-lethal approach to assess whether persistent contaminants are being accumulated during the juvenile to adult phase of salmonids originating from UK rivers.
... C-MH), A-fibre mechanonociceptor (AM), C-fiber low-threshold mechanoreceptor (C-LTMR), Aβ-fiber slowly-adapting type I and type II LTMR (SA-I LTMR and SA-II LTMR), Aβ-fibre rapidly-adapting type I and type II LTMR (RA-I LTMR and RA-II LTMR). Marker genes were extracted from literature[35][36][37][38][39][40][41][42][43][44][45][46][47]65,92,93], figure is adapted from[35]. ...
In stock enhancement and sea-ranching procedures, the adipose fin of hundreds of millions of salmonids is removed for marking purposes annually. However, recent studies proved the significance of the adipose fin as a flow sensor and attraction feature. In the present study, we profiled the specific expression of 20 neuron- and glial cell-marker genes in the adipose fin and seven other tissues (including dorsal and pectoral fin, brain, skin, muscle, head kidney, and liver) of the salmonid species rainbow trout Oncorhynchus mykiss and maraena whitefish Coregonus maraena. Moreover, we measured the transcript abundance of genes coding for 15 mechanoreceptive channel proteins from a variety of mechanoreceptors known in vertebrates. The overall expression patterns indicate the presence of the entire repertoire of neurons, glial cells and receptor proteins on the RNA level. This quantification suggests that the adipose fin contains considerable amounts of small nerve fibers with unmyelinated or slightly myelinated axons and most likely mechanoreceptive potential. The findings are consistent for both rainbow trout and maraena whitefish and support a previous hypothesis about the innervation and potential flow sensory function of the adipose fin. Moreover, our data suggest that the resection of the adipose fin has a stronger impact on the welfare of salmonid fish than previously assumed.
... The stress generated by this technique was avoided by the involvement of anglers obtaining tissue samples from their own catch. In addition to avoiding animal distress caused by electrofishing (Buckland-Nicks, Gillis, & Reimchen, 2012), angler contributions decreased the sampling effort and covered areas where electrofishing would not be effective. The introduction of a citizen science approach also addressed the logistical and financial limitations of monitoring. ...
Many freshwater non‐indigenous species (NISs) are stocked for recreational fishing, in some cases illegally in protected areas. In this study, fish communities were monitored using environmental DNA, electrofishing and anglers’ catches as the sources of samples in a mountainous Biosphere Reserve in Asturias (northern Spain), where stocking is forbidden.
Three NISs have been introduced illegally in the protected area and have shown increasing populations in the last two decades. Two species used as fishing bait, Squalius carolitertii (chub) and Phoxinus phoxinus (minnow), are expanding in running waters. Oncorhynchus mykiss (rainbow trout) was also detected and is likely to have been introduced for angling or from fish farm escapes.
The results suggest that sustained illegal stocking contributed to the increase of the three NISs. In contrast, Salmo trutta (brown trout) of northern European lineages, identified from *90 alleles at the LDH‐C1 locus, and formerly legally stocked for angling, is decreasing, most likely as a result of climate change. Climate change could also contribute to the expansion of the two non‐indigenous cyprinids to colder upstream areas.
Through the application of a social survey, it was found that unlike other population groups, anglers in the region significantly preferred stocking over environmental improvement for the management of fish populations. The results obtained suggest that raising the awareness of anglers about the importance of safeguarding native fish species could help to prevent the spread of NISs in protected areas.
... Another source of disparity in ostariophysan fin configurations is the presence/absence of the adipose fin, which is usually a small, primitively non-rayed fin located medially between the dorsal and caudal fins (Aiello, Stewart, & Hale, 2016;Buckland-Nicks, Gillis, & Reimchen, 2012;Reimchen & Temple, 2004;Stewart, 2015). The ad- ...
Fishes are both extremely diverse and morphologically disparate. Part of this disparity can be observed in the numerous possible fin configurations that may differ in terms of the number of fins as well as fin shapes, sizes and relative positions on the body. Here, we thoroughly review the major patterns of disparity in fin configurations for each major group of fishes and discuss how median and paired fin homologies have been interpreted over time. When taking into account the entire span of fish diversity, including both extant and fossil taxa, the disparity in fin morphologies greatly complicates inferring homologies for individual fins. Given the phylogenetic scope of this review, structural and topological criteria appear to be the most useful indicators of fin identity. We further suggest that it may be advantageous to consider some of these fin homologies as nested within the larger framework of homologous fin‐forming morphogenetic fields. We also discuss scenarios of appendage evolution and suggest that modularity may have played a key role in appendage disparification. Fin modules re‐expressed within the boundaries of fin‐forming fields could explain how some fins may have evolved numerous times independently in separate lineages (e.g., adipose fin), or how new fins may have evolved over time (e.g., anterior and posterior dorsal fins, pectoral and pelvic fins). We favour an evolutionary scenario whereby median appendages appeared from a unique field of competence first positioned throughout the dorsal and ventral midlines, which was then redeployed laterally leading to paired appendages.
... The removal of the adipose fin in salmonids is a common procedure used particularly for distinguishing between hatchery-reared and wild fishes. The adipose fin lacks musculature and skeletal structures; however, its assumed vestigial role has recently been challenged with evidence of extensive nervous tissue and mechanosensory function (Aiello et al. 2016;Buckland-Nicks et al. 2012;Buckland-Nicks, 2016). ...
Fishes are used in a wide range of scientific studies, from conservation research with potential benefits to the species used to biomedical research with potential human benefits. Fish research can take place in both laboratories and field environments and methods used represent a continuum from non‐invasive observations, handling, through to experimental manipulation. While some countries have legislation or guidance regarding the use of fish in research, many do not and there exists a diversity of scientific opinions on the sentience of fish and how we determine welfare. Nevertheless, there is a growing pressure on the scientific community to take more responsibility for the animals they work with through maximising the benefits of their research to humans or animals while minimising welfare or survival costs to their study animals. In this review, we focus primarily on the refinement of common methods used in fish research based on emerging knowledge with the aim of improving the welfare of fish used in scientific studies. We consider the use of anaesthetics and analgesics and how we mark individuals for identification purposes. We highlight the main ethical concerns facing researchers in both laboratory and field environments and identify areas that need urgent future research. We hope that this review will help inform those who wish to refine their ethical practices and stimulate thought among fish researchers for further avenues of refinement. Improved ethics and welfare of fishes will inevitably lead to increased scientific rigour and is in the best interests of both fishes and scientists.
... However, phylogenetic studies show that the adipose fins have originated repeatedly and are a functional and not a vestigial structure (Stewart et al. 2014). There is growing evidence that adipose fins may act as a precaudal sensory organ (Reimchen & Temple 2004;Buckland-Nicks et al. 2012;Aiello et al. 2016). Adipose fins may also influence the manoeuvring abilities of fish in turbulent water (Reimchen & Temple 2004), as well as playing a role during courtship. ...
... Such effects can be mitigated by optimization of anaesthesia handling and logistics, as well as by aeration and quality testing of the water in the tanks. As the adipose fin is innervated (Buckland-Nicks et al. 2012), it is likely that the fish may feel pain after recovery from anaesthesia, but the intensity and duration of this pain is unknown. ...
... advarer-mot-finneklipping/. Adipose fin clipping has been reported to affect swimming behaviour of small Pacific salmon (Buckland-Nicks et al. 2012). As far as we know, studies have not been done on Atlantic salmon, but since the adipose fin is believed to be a water-flow sensor in turbulent water, salmon in tanks and cages should not be seriously affected by the lack of adipose fin. ...
Escaped farmed Atlantic salmon (Salmo salar) is considered a threat to wild salmon. In order to take action to reduce the impact of escapees, methods to distinguish escapees from wild fish and to trace them back to their origin are in demand. This paper gives an overview of available methods and discusses the impact on fish welfare, both in the short-and long-term. Adipose fin clipping, freeze branding, different external and internal tags, as well as natural and chemical marks are considered. All marking procedures that involve handling of fish have an impact on fish welfare. Spraying with pigments and most externally attached tags significantly reduce the welfare, both on short-term and long-term perspectives. Although the use of natural or chemical marks, like exposure to stable isotopes via egg immersion or vaccination, involves no or no extra handling , subsequent analysis may require killing the fish after catch. Large-scale marking with implanted or external tags could represent higher risks of human errors and reduced fish welfare, as opposed to small-scale marking. In general, the knowledge about effects of marking on fish welfare is limited for most of the available methods, in particular regarding other effects than mortality and growth reductions.
... These data show that novel appendages can evolve by individuation of a domain of a plesiomorphic fin fold. Additionally, adipose fins that develop from the LMFF can evolve skeleton 4,33,44 , musculature 32 , and sensory anatomy (here and 45,46 ). For example, in C. aeneus the domain of the LMFF that contributes to the adipose fin is transformed over ontogeny by the apparent migration of mesenchymal cells into the territory and also the growth of new fin-associated nerves into the fin membrane. ...
... The adipose fin of the brown trout, Salmo trutta (Salmonidae), a euteleost, is also invested with sensory nerve fibers and also hypothesized to detect fin movement 45,46,66,67 . These nerves terminate upon associated astrocyte-like cells, which are hypothesized to detect the deformation of collagen fibers that span the left-and-right sides of the adipose fin 45,46 . ...
... The adipose fin of the brown trout, Salmo trutta (Salmonidae), a euteleost, is also invested with sensory nerve fibers and also hypothesized to detect fin movement 45,46,66,67 . These nerves terminate upon associated astrocyte-like cells, which are hypothesized to detect the deformation of collagen fibers that span the left-and-right sides of the adipose fin 45,46 . The organization of collagen is similar to what has been described in the LMFF of D. rerio 68 , indicating that many structural components of the LMFF are retained over ontogeny and that sensory anatomy is reorganized over ontogeny in this lineage, similar to C. aeneus. ...
The dorsal, anal and caudal fins of vertebrates are proposed to have originated by the partitioning and transformation of the continuous median fin fold that is plesiomorphic to chordates. Evaluating this hypothesis has been challenging, because it is unclear how the median fin fold relates to the adult median fins of vertebrates. To understand how new median fins originate, here we study the development and diversity of adipose fins. Phylogenetic mapping shows that in all lineages except Characoidei (Characiformes) adipose fins develop from a domain of the larval median fin fold. To inform how the larva’s median fin fold contributes to the adipose fin, we study Corydoras aeneus (Siluriformes). As the fin fold reduces around the prospective site of the adipose fin, a fin spine develops in the fold, growing both proximally and distally, and sensory innervation, which appears to originate from the recurrent ramus of the facial nerve and from dorsal rami of the spinal cord, develops in the adipose fin membrane. Collectively, these data show how a plesiomorphic median fin fold can serve as scaffolding for the evolution and development of novel, individuated median fins, consistent with the median fin fold hypothesis.
... The patchy occurrence that are adipose fins and varied skeletal compositions in teleosts adapted to a wide range of environments renders the evolutionary and functional significance of this structure difficult to interpret. Most likely it directs pre-caudal water flow, or serves as a flow sensor (Buckland-Nicks et al., 2011). ...
The postcranial skeleton of vertebrates fulfils various tasks constrained by extrinsic and intrinsic requirements, which significantly differ between fishes and tetrapods. For instance, body support, storage of minerals, and haematopoiesis are less important for fishes, which include more than half of all living vertebrates, than for tetrapods. Evolutionary and developmental aspects of the various parts of the postcranial skeleton of fishes that perform many different functions, however, have received only limited attention. Our knowledge is limited in anatomical, morphological or taxonomic scope, in part because the composition of the postcranial
skeleton differs significantly between fish lineages such as ‘agnathans’, chondrichthyans, actinopterygians, dipnoans and coelacanths. Here, we provide a broad overview of the evolutionary development of the postcranial skeleton of all extinct and extant fish lineages in a phylogenetic and genetic framework. It is obvious that our knowledge
about the evolution and development of cartilage and bone formation, as well as the evolutionary sequence of postcranial parts, increased in recent years but, nevertheless, remains incomplete. Different roadmaps for future research topics emerge from this review.
