Sensory Biology Research Papers - Academia.edu (original) (raw)

2025, Integrative Zoology

Despite over 70 years of research on shark repellents, few practical and reliable solutions to prevent shark attacks on humans or reduce shark bycatch and depredation in commercial fisheries have been developed. In large part, this deficiency stems from a lack of fundamental knowledge of the sensory cues that drive predatory behavior in sharks. However, the widespread use of shark repellents is also hampered by the physical constraints and technical or logistical difficulties of deploying substances or devices in an open-water marine environment to prevent an unpredictable interaction with a complex animal. Here, we summarise the key attributes of the various sensory systems of sharks and highlight residual knowledge gaps that are relevant to the development of effective shark repellents. We also review the most recent advances in shark repellent technology within the broader historical context of research on shark repellents and shark sensory systems. We conclude with suggestions for future research that may enhance the efficacy of shark repellent devices, in particular, the continued need for basic research on shark sensory biology and the use of a multi-sensory approach when developing or deploying shark repellent technology.

2025, Marine Ecology Progress Series

Benthic crustaceans such as the blue crab Callinectes sapidus use various sensory appendages to navigate chemical plumes. We characterized the role of different sensory structures in blue crabs during olfactory search by deafferenting (i.e. removing or rendering inactive) particular sensor populations and by quantifying odor-plume structure and flow dynamics. Our results indicate that blue crabs use both cephalic and thoracic appendages for olfactory-mediated orientation. Cephalic chemosensor deafferentation decreased search success, reduced walking speed and increased the duration of stationary periods. All these deficiencies are manifestations of the inability of crabs to sustain upstream progress. Crabs subjected to deafferentation of thoracic sensilla failed to correctly track the narrowing plume and showed an increased frequency of large course-corrections. Whereas cephalic sensors clearly function in motivating upstream movement during the search process, thoracic receptors aid in source localization. The differing functional roles of these 2 sets of appendages may be associated with different signal characteristics impinging on their chemosensor populations. Intermittent but intense signals received by the cephalic appendages may enable the crabs to identify attractive odors and sustain searching. Chemical signals impinging on legs are more homogeneous and may allow the crabs to acquire better information on the spatial patterns of chemical signal structure that are important for navigation. The simultaneous use of chemical signals at differing heights in the plume suggest that the 3D structure of these plumes is important for foraging success, and that different populations of neural receptors may be tuned to operate optimally in particular signal environments.

2025, Marine Ecology Progress Series

2024, BMC Genomics

Background: While leeches in the genus Hirudo have long been models for neurobiology, the molecular underpinnings of nervous system structure and function in this group remain largely unknown. To begin to bridge this gap, we performed RNASeq on pools of identified neurons of the central nervous system (CNS): sensory T (touch), P (pressure) and N (nociception) neurons; neurosecretory Retzius cells; and ganglia from which these four cell types had been removed. Results: Bioinformatic analyses identified 3565 putative genes whose expression differed significantly among the samples. These genes clustered into 9 groups which could be associated with one or more of the identified cell types. We verified predicted expression patterns through in situ hybridization on whole CNS ganglia, and found that orthologous genes were for the most part similarly expressed in a divergent leech genus, suggesting evolutionarily conserved roles for these genes. Transcriptional profiling allowed us to identify candidate phenotype-defining genes from expanded gene families. Thus, we identified one of eight hyperpolarization-activated cyclic-nucleotide gated (HCN) channels as a candidate for mediating the prominent sag current in P neurons, and found that one of five inositol triphosphate receptors (IP3Rs), representing a sub-family of IP3Rs absent from vertebrate genomes, is expressed with high specificity in T cells. We also identified one of two piezo genes, two of~65 deg/enac genes, and one of at least 16 transient receptor potential (trp) genes as prime candidates for involvement in sensory transduction in the three distinct classes of leech mechanosensory neurons. Conclusions: Our study defines distinct transcriptional profiles for four different neuronal types within the leech CNS, in addition to providing a second ganglionic transcriptome for the species. From these data we identified five gene families that may facilitate the sensory capabilities of these neurons, thus laying the basis for future work leveraging the strengths of the leech system to investigate the molecular processes underlying and linking mechanosensation, cell type specification, and behavior.

2024, Conservation Physiology

Incidental capture, or bycatch, in fisheries represents a substantial threat to the sustainability of elasmobranch populations worldwide. Consequently, researchers are increasingly investigating elasmobranch bycatch reduction methods, including some focused on these species' sensory capabilities, particularly their electrosensory systems. To guide this research, we review current knowledge of elasmobranch sensory biology and feeding ecology with respect to fishing gear interactions and include examples of bycatch reduction methods used for elasmobranchs as well as other taxonomic groups. We discuss potential elasmobranch bycatch reduction strategies for various fishing gear types based on the morphological, physiological, and behavioural characteristics of species within this diverse group. In select examples, we indicate how an understanding of the physiology and sensory biology of vulnerable, bycatch-prone, non-target elasmobranch species can help in the identification of promising options for bycatch reduction. We encourage collaboration among researchers studying bycatch reduction across taxa to provide better understanding of the broad effects of bycatch reduction methods.

2024, Papéis Avulsos de Zoologia

The cephalic portions of the latero-sensory canal system in Denticeps clupeoides are described and analyzed. The species, a small herring-like fish from relictual West African streams, is the most primitive living clupeomorph and sole Recent representative of suborder Denticipitoidei. As sister group to over 360 species in Clupeoidei, Denticeps is a key taxon in understanding clupeomorph and lower teleostean relationships. Observations on recently-collected specimens of Denticeps clupeoides revealed comparatively-important and previously-unrecorded details of the cephalic latero-sensory canals which are relevant for understanding relationships at different levels in clupeomorph phylogeny. The infraorbital, supraorbital, preopercular, extrascapular and post-temporal canals of Denticeps have unbranched tubules in soft tissue, as in the hypothesized plesiomorphic condition for lower teleosts. Contrastingly, the presence of a complex network formed by a high order of branching of cephal...

2024, Scientific Reports

Coleoid cephalopods camouflage on timescales of seconds to match their visual surroundings. To date, studies of cephalopod camouflage-to-substrate have been focused primarily on benthic cuttlefish and octopus, because they are readily found sitting on the substrate. In contrast to benthic cephalopods, oval squid (Sepioteuthis lessoniana species complex) are semi-pelagic animals that spend most of their time in the water column. In this study, we demonstrate that in captivity, S. lessoniana Sp.2 (Shiro-ika, white-squid) from the Okinawa archipelago, Japan, adapts the coloration of their skin using their chromatophores according to the background substrate. We show that if the animal moves between substrates of different reflectivity, the body patterning is changed to match. Chromatophore matching to substrate has not been reported in any loliginid cephalopod under laboratory conditions. Adaptation of the chromatophore system to the bottom substrate in the laboratory is a novel experimental finding that establishes oval squid as laboratory model animals for further research on camouflage.

2024, bioRxiv (Cold Spring Harbor Laboratory)

While leeches in the genus Hirudo have long been models for neurobiology, the molecular underpinnings of nervous system structure and function in this group remain largely unknown. To begin to bridge this gap, we performed RNASeq on pools of identified neurons of the central nervous system (CNS): sensory T (touch), P (pressure) and N (nociception) neurons; neurosecretory Retzius cells; and ganglia from which these four cell types had been removed. Bioinformatic analyses identified 2,812 putative genes whose expression differed significantly among the samples. These genes clustered into 7 groups which could be associated with one or more of the identified cell types. We verified predicted expression patterns through in situ hybridization on whole CNS ganglia, and found that orthologous genes were for the most part similarly expressed in a divergent leech genus, suggesting evolutionarily conserved roles for these genes. Transcriptional profiling allowed us to identify candidate phenotype-defining genes from expanded gene families. Thus, we identified one of eight hyperpolarization-activated cyclic-nucleotide gated (HCN) channels as a candidate for mediating the prominent sag current in P neurons, and found that one of five inositol triphosphate receptors (IP3Rs), representing a sub-family of IP3Rs absent from vertebrate genomes, is expressed with high specificity in T cells. We also identified one of two piezo genes, two of ~65 deg/enac genes, and one of at least 16 transient receptor potential (trp) genes as prime candidates for involvement in sensory transduction in the three distinct classes of leech mechanosensory neurons.

2024, Journal of Marine Science and Technology

Many shark bites to humans, including fatalities, have involved surfers. Various personal shark deterrents are commercially available to surfers, including Rpela v2, which is a battery-powered device fitted to a surfboard. It produces an electric field around the surfer aimed at deterring sharks from approaching or biting by disrupting their electroreception organs. The device was tested on white sharks (Carcharodon carcharias) at Salisbury Island, Western Australia. In total, 46 trials were done with the Rpela v2 either active or not active to determine the device's effect on sharks' response to a floating board with fish bait attached (to tempt a bite). When active, Rpela v2 significantly reduced the probability of a bite (0.75 to 0.25, a 66% reduction) and interaction (i.e. bite or touch) (0.80 to 0.50, a 38% reduction) occurring compared with when it was inactive. The number of passes taken by a shark also reduced and the mean distance between the shark and the bait increased when Rpela v2 was active. It is noted that Rpela v2 did not completely remove the risk of shark bite, but the magnitude of the reduction in risk is of a level that surfers are likely to consider meaningful and it could be expected that Rpela v2 would provide more time for surfers to leave the water (i.e. as inferred from the number of passes) when a potentially dangerous shark is present. Implications for the role of personal deterrents in strategic management of the risk of shark bite are also discussed.

2024, Fish and Fisheries

Estimated declines in shark and ray populations worldwide have raised major, widespread concern about the impacts of global fisheries on elasmobranchs. The mechanisms causing elasmobranch mortality during fisheries' capture are not fully understood, but we must gain greater clarity on this topic for fisheries managers to develop effective conservation plans to mitigate further population declines. To evaluate how two important factors, respiratory mode and fishing gear type, impact elasmobranch survival, we compiled publicly available data sources on the immediate mortality percentages of 83 species and post-release mortality percentages of 40 species. Using Bayesian models, we found that sharks and rays captured in longlines had significantly lower immediate mortality than those caught in trawls or gillnets. Our models also predicted the mean total discard mortality (combined immediate and post-release mortality) percentages of obligate ram-ventilating elasmobranchs caught in longline, gillnet and trawl gear types to be 49.8, 79.0 and 84.2%, respectively. In contrast, total discard mortality percentages of stationary-respiring species were significantly lower (longline capture mean = 7.2%, gillnet capture mean = 25.3%, trawl capture mean = 41.9%). Our global metaanalysis provides the first quantified demonstration of how mortality is affected by these two factors across a broad range of species. Our results and approach can be applied to data-deficient elasmobranchs and fisheries to identify species that are likely to experience high rates of mortality due to respiratory mode and/or fishing methods used, so that appropriate mitigation measures can be prioritized and investigated.

2023

Collate and review information from National Regulation 812/2004 reports and elsewhere relating to the implementation of bycatch mitigation measures and ongoing bycatch mitigation trials, compile recent results and coordinate further work... more

2023, Zoology

Volume 106 www.urbanfischer.de/journals/zoology 1 thin trailing edge. Although the shape of the cephalofoil strongly suggests a hydrodynamic lift function, this possibility has never been tested (Budker, 1971). The cephalofoil also provides an ideal planing surface which could be banked and lifted to provide a significant turning force at the anterior end of the shark, where it would be most effective in causing a change in direction (Nakaya, 1995). We address the second of these proposals, namely, that the cephalofoil head morphology provides a hydrodynamic maneuvering advantage over the more usual shark head design (Murphy and Nichols, 1916). Hammerhead sharks are a clade with worldwide distribution, with cephalofoils ranging in width from 40-50% of total length (Eusphyra blochii) to just 18-21% of total length (Sphyrna tiburo; Compagno, 1988). The variation in head morphology within the Sphyrnidae enables comparisons to be made between intermediate and extreme head morphologies. The hammerheads are nested within a group of sharks with normal, pointed heads, the requiem sharks (Carcha

2023, Aquatic Conservation: Marine and Freshwater Ecosystems

Following a shark attack, local governments often rapidly respond by implementing indiscriminate shark culls. These culls have been demonstrated to have substantial localized and adverse effects on a variety of marine organisms, and therefore there is an increasing need for an eco‐friendly alternative that maximizes both beachgoer and marine organismal safety. In response to such culls, the novel magnetic barrier technology, the Sharksafe Barrier was developed and rigorously tested on a variety of sharks implicated in shark attacks (e.g. bull sharks – Carcharhinus leucas and white sharks – Carcharodon carcharias). Although these studies exhibited promise in shark swim pattern manipulation and C. leucas exclusion, research was lacking in assessing if the technology could serve as an alternative to shark nets, or more specifically, if it could exclude motivated C. carcharias from bait. Using a 13 m × 13 m square exclusion zone, this study aimed to test the C. carcharias exclusion capa...

2023, Ocean & Coastal Management

Since the sinking of the USS Indianapolis (CA-35) and associated shark attacks in 1945, the quest to find an effective shark repellent has been endless. Early efforts were focused on finding a shark repellent which would minimize the probability of a shark attack. However, studies illustrate that shark populations are drastically declining which has led to calls for effective management policies and practices to reduce both directed catch and bycatch of various shark species. With increased need for shark conservation, the focus has shifted to protecting sharks from harmful anthropogenic pressures, such as fishing gear and beach nets. Current shark repellent technologies which aim to minimize elasmobranch mortality in fishing gears include: permanent magnets, electropositive metal (EPM) alloys, and semiochemicals. This paper will review present electrosensory and semiochemical shark repellents, the mechanisms of elasmobranch (e.g. shark, skate and ray) detection and repellency, species-specificity in elasmobranch response to the stimuli, and environmental and biological conditions which may influence repellent success. Future research to enhance our knowledge on electrosensory repellents and to improve the success of repellent implementation and application will be discussed.

2023, The Journal of experimental biology

Prey fish possess a remarkable ability to sense and evade an attack from a larger fish. Despite the importance of these events to the biology of fishes, it remains unclear how sensory cues stimulate an effective evasive maneuver. Here, we show that larval zebrafish (Danio rerio) evade predators using an escape response that is stimulated by the water flow generated by an approaching predator. Measurements of the high-speed responses of larvae in the dark to a robotic predator suggest that larvae respond to the subtle flows in front of the predator using the lateral line system. This flow, known as the bow wave, was visualized and modeled with computational fluid dynamics. According to the predictions of the model, larvae direct their escape away from the side of their body exposed to more rapid flow. This suggests that prey fish use a flow reflex that enables predator evasion by generating a directed maneuver at high speed. These findings demonstrate a sensory-motor mechanism that u...

2023, Journal of Marine Science and Technology

2023, Journal of Fish Biology

It has long been assumed that the elongated rostra (the saws) of sawsharks (family: Pristiophoridae) and sawfish (family: Pristidae) serve a similar function. Recent behavioural and anatomical studies have shed light on the dual function of the pristid rostrum in mechanosensory and electrosensory prey detection and prey manipulation. Here, the authors examine the distributions of the mechanosensory lateral line canals and electrosensory ampullae of Lorenzini in the southern sawshark, Pristiophorus nudipinnis and the longnose sawshark, Pristiophorus cirratus. In both species, the receptive fields of the mechano‐ and electrosensory systems extend the full length of the rostrum indicating that the sawshark rostrum serves a sensory function. Interestingly, despite recent findings suggesting they feed at different trophic levels, minimal interspecific variation between the two species was recorded. Nonetheless, compared to pristids, the pristiophorid rostrum possesses a reduced mechanose...

2023, PLOS ONE

In the aquatic environment, living organisms emit weak dipole electric fields, which spread in the surrounding water. Elasmobranchs detect these dipole electric fields with their highly sensitive electroreceptors, the ampullae of Lorenzini. Freshwater sawfish, Pristis microdon, and two species of shovelnose rays, Glaucostegus typus and Aptychotrema rostrata were tested for their reactions towards weak artificial electric dipole fields. The comparison of sawfishes and shovelnose rays sheds light on the evolution and function of the elongated rostrum ('saw') of sawfish, as both groups evolved from a shovelnose ray-like ancestor. Electric stimuli were presented both on the substrate (to mimic benthic prey) and suspended in the water column (to mimic free-swimming prey). Analysis of around 480 behavioural sequences shows that all three species are highly sensitive towards weak electric dipole fields, and initiate behavioural responses at median field strengths between 5.15 and 79.6 nVcm 21. The response behaviours used by sawfish and shovelnose rays depended on the location of the dipoles. The elongation of the sawfish's rostrum clearly expanded their electroreceptive search area into the water column and enables them to target free-swimming prey.

2023, Marine and Freshwater Research

To investigate factors contributing to immediate mortality in gill-net-caught elasmobranchs, we caught and blood sampled a total of 64 sharks and rays. Blacktip reef sharks (Carcharhinus melanopterus) were the most commonly caught species and had significantly elevated plasma lactate (mean 23.3 mM) and potassium (mean 6.2 mM) concentrations following capture, suggesting physiological disturbance. The overall immediate mortality rate of C. melanopterus was 38% and mortality was significantly influenced by body size, but not location of entanglement or sex. Of the other species caught, nervous sharks (Carcharhinus cautus) were of particular concern, because this species is often caught as bycatch by gill-net fisheries throughout its range and experienced high immediate mortality rates when captured (66%; n = 12) in the present study. The results suggest that juvenile C. melanopterus are particularly susceptible to gill-net-related mortality and that fisheries management strategies for...

2023, Fisheries Research

The blue shark (Prionace glauca) populations are globally decreasing and the blue shark has been classified as near threatened. However it is the main species in the Spanish and Portuguese longline fisheries catches and targeted by a part of these fisheries in the northeastern Atlantic Ocean. Sharks locate their prey using electric sense. The use of magnets as a repellent for shark fisheries was previously proposed as a measure of conservation. This is the first paper describing the magnetic effect on blue shark catch. In this study, we tested during 3 days under real fishing conditions 2 models of magnets made of neodymium with high resistance in time and magnet power. The results of our tests showed that magnets did not decrease catches of blue shark and can even have an attraction effect. This effect was significantly higher for the large magnet model tested (26 mm x 11 mm x 12 mm, 0,885 tesla) compared to the smaller one (20 mm x 13 mm x 15 mm, 0,464 tesla). Physical measurements were associated with this study and also revealed an important practical aspect to be taken into account in this kind of experiments: that hooks remain magnetized after removal of the magnets and are even slightly magnetized without any previous contact with a magnet.

2023, Journal of Marine Science and Technology

2023, Global Ecology and Conservation

Despite bycatch of elasmobranch (sharks and rays) being a major concern in most fisheries worldwide, there is a lack of knowledge on their spatio-temporal species distribution, biology (life stage and sex-ratios), as well as their at-haulback mortality rate. Observer data from the French and Spanish tropical purse-seine tuna fisheries operating in the eastern Atlantic and western Indian Oceans between 2005 and 2017 were analysed to investigate elasmobranch bycatch. Data included 24 elasmobranchs species and distribution patterns of catch per unit of effort (CPUE) by species and sex-ratio were found to vary with life stages, areas, seasons and fishing modes. In general, higher catches were found in FADassociated sets (>40%) than free tuna school sets (<17%) although this can vary depending on the species. For the large majority of species, a high proportion of juveniles were caught (30.7e100%), apparent at-haulback mortality rates was high (24.3e63.9%) and finally sex ratios was unbalanced (13.3e66.7% of females). Areas and seasons identified from these different components should be of interest for the monitoring and management of elasmobranch bycatches.

2023, Endangered Species Research

2023, Insects

Dragonflies are hemimetabolous insects, switching from an aquatic life style as nymphs to aerial life as adults, confronted to different environmental cues. How sensory structures on the antennae and the brain regions processing the incoming information are adapted to the reception of fundamentally different sensory cues has not been investigated in hemimetabolous insects. Here we describe the antennal sensilla, the general brain structure, and the antennal sensory pathways in the last six nymphal instars of Libellula depressa, in comparison with earlier published data from adults, using scanning electron microscopy, and antennal receptor neuron and antennal lobe output neuron mass-tracing with tetramethylrhodamin. Brain structure was visualized with an anti-synapsin antibody. Differently from adults, the nymphal antennal flagellum harbors many mechanoreceptive sensilla, one olfactory, and two thermo-hygroreceptive sensilla at all investigated instars. The nymphal brain is very simi...

2023, Journal of Chemical Ecology

Yellowfin tuna enhance their hunting success in the vast pelagic environment by using their sense of smell to detect intact (uninjured) prey that are beyond visual range. However, the olfactory cues that tuna use would normally face huge and rapid dilution in the open ocean. We demonstrate that these prey odors are complexed within biologically derived lipid structures that probably delay the dilution of the amino acids to subthreshold concentrations and provide persistent arousal and search cues for the tuna. This may be the first demonstration of an extracorporeal biological function for liposomes. Tuna may also form "chemical search images" to maximize feeding efficiency. We demonstrate that the amino acid profiles of various prey species are consistent over time and between schools, which makes the formation of search images feasible.

2023, Endangered Species Research

Sawfishes are among the most threatened families of marine fishes and are susceptible to incidental capture in net fisheries. Since bycatch reduction devices currently used in trawl fisheries are not effective at reducing sawfish catches, new methods to minimise sawfish bycatch are needed. Ideally, these should affect sawfish behaviour and prevent contact with the fishing gear. We tested the effects of electric fields on sawfish behaviour to assess the potential of electric pulses in mitigating sawfish bycatch. Experiments were conducted in a tank where 2 electrodes were suspended in the water column, connected to a pulse generator, and placed across the swimming path of sawfish. Two largetooth sawfish Pristis pristis were tested in control conditions, in the presence of a baseline pulse, and of 5 variations of that pulse where 1 parameter (polarity, voltage, frequency, pulse shape, pulse duration) was altered at a time. Conditional inference trees were used to identify the effects ...

2023, Journal of Experimental Biology

Squid are mobile, diverse, ecologically important marine organisms whose behavior and habitat use can have substantial impacts on ecosystems and fisheries. However, due in part to the inherent challenges of monitoring squid in their natural marine environment, fine-scale behavioral observations of these free-swimming, soft-bodied animals are rare. Bio-logging tags provide an emerging way to remotely study squid behavior in their natural environments. Here we apply a novel, high-resolution bio-logging tag (ITAG) to seven veined squid Loligo forbesi in a controlled experimental environment to quantify their short-term (24-hr) behavioral patterns. Tag accelerometer, magnetometer and pressure data were used to develop automated gait classification algorithms based on overall dynamic body acceleration, and a subset of the events were assessed and confirmed using concurrently collected video data. Finning, flapping, and jetting gaits were observed, with the low-acceleration finning gaits ...

2023, Invertebrate Biology

Cephalopod skin is soft, flexible, and produces rapid color changes for camouflage and signaling primarily by regulating the shapes of its numerous chromatophore organs. Each chromatophore has 10-30 radial muscle cells, termed fibers, under central nervous system control. Each fiber contains myofilaments that contract in concert to stretch the pigment-containing cell from its punctate, spherical state to a fully expanded thin disk of color. Expansion occurs in less than one second and can result in a 14-fold expansion in pigment cell diameter. We investigated the anchoring mechanism of radial muscle fibers that expand pigment cells in the longfin squid, Doryteuthis (Loligo) pealeii. The proximal Active Zone of a radial muscle fiber adheres to the pigment cell within an ensheathing sinus. The distal portion forms terminal arbors, thereby increasing the surface area, to adhere it to the dermal extracellular matrix (ECM). While the muscle fiber is attached to the pigment cell with haptosomes, the remainder of the fiber is adhered to the surrounding basal lamina (part of the ECM) by numerous, closely spaced, small costamere-like projections. Branching of the radial muscle fiber termini and the costamere-like attachments are key anatomical specializations that anchor the radial muscle fibers in the pliable skin while allowing the freedom of movement required for large changes in pigment cell diameter. We postulate that these features may be relevant for the development of soft actuation models in materials science.

2023, Global Ecology and Conservation

2022, SR Vol.57(04) [April 2020]

2022

The mission of the National Oceanic and Atmospheric Administration (NOAA) is to understand and predict changes in the Earth=s environment and to conserve and manage coastal and oceanic marine resources and habitats to help meet our Nation=s economic, social, and environmental needs. As a branch of NOAA, the National Marine Fisheries Service (NMFS) conducts or sponsors research and monitoring programs to improve the scientific basis for conservation and management decisions. NMFS strives to make information about the purpose, methods, and results of its scientific studies widely available. NMFS = Pacific Islands Fisheries Science Center (PIFSC) uses the NOAA Technical Memorandum NMFS series to achieve timely dissemination of scientific and technical information that is of high quality but inappropriate for publication in the formal peerreviewed literature. The contents are of broad scope, including technical workshop proceedings, large data compilations, status reports and reviews, l...

2022, Journal of Comparative Physiology A

Blind cavefish use a form of active sensing in which burst-coast swimming motions generate flow signals detected by the lateral line. To determine if blind cavefish have evolved behavioral specializations for active flowsensing, including the ability to regulate flow signal production through lateral line feedback, the swimming kinematics of blind and sighted morphs of Astyanax were compared before and after 24 h of familiarization with a novel, dark environment and with and without lateral line functionality. Although both morphs showed little difference in the vast majority of kinematic parameters measured, blind morphs differed significantly from sighted morphs in having a much higher incidence of swim cycle sequences devoid of sharp turns. Both lateral line deprivation and familiarization with the arena led to significant declines in this number for blind, but not sighted morphs. These findings suggest that swimming kinematics are largely conserved, but that blind morphs have nevertheless evolved enhanced abilities to use lateral line feedback when linking swim cycles into continuous, straight trajectories for exploratory purposes. This behavioral specialization can best be understood in terms of the intermittent and short-range limitations of active flow-sensing and the challenges they pose for spatial orientation and navigation.

2022, PLoS ONE

The electrosense of sharks and rays is used to detect weak dipole-like bioelectric fields of prey, mates and predators, and several models propose a use for the detection of streaming ocean currents and swimming-induced fields for geomagnetic orientation. We assessed pore distributions, canal vectors, complementarity and possible evolutionary divergent functions for ampullary clusters in two sharks, the scalloped hammerhead (Sphyrna lewini) and the sandbar shark (Carcharhinus plumbeus), and the brown stingray (Dasyatis lata). Canal projections were determined from measured coordinates of each electrosensory pore and corresponding ampulla relative to the body axis. These species share three ampullary groups: the buccal (BUC), mandibular (MAN) and superficial ophthalmic (SO), which is subdivided into anterior (SOa) and posterior (SOp) in sharks. The stingray also has a hyoid (HYO) cluster. The SOp in both sharks contains the longest (most sensitive) canals with main projections in the posterior-lateral quadrants of the horizontal plane. In contrast, stingray SO canals are few and short with the posterior-lateral projections subsumed by the HYO. There was strong projection coincidence by BUC and SOp canals in the posterior lateral quadrant of the hammerhead shark, and laterally among the stingray BUC and HYO. The shark SOa and stingray SO and BUC contain short canals located anterior to the mouth for detection of prey at close distance. The MAN canals of all species project in anterior or posterior directions behind the mouth and likely coordinate prey capture. Vertical elevation was greatest in the BUC of the sandbar shark, restricted by the hammerhead cephalofoil and extremely limited in the dorsoventrally flattened stingray. These results are consistent with the functional subunit hypothesis that predicts specialized ampullary functions for processing of weak dipole and geomagnetic induced fields, and provides an anatomical basis for future experiments on central processing of different forms of relevant electric stimuli.

2022, BIOVALENTIA: Biological Research Journal

A recent study to providing valid checklist of stingrays species in South Sumatran waters provide 14 species: Brevitrygon heterura, Fluvitrygon kittipongi, Fluvitrygon oxyrhyncha, Fluvitrygon signifier, Fluvitrygon sp ‘musi’ 1, Fluvitrygon sp ‘musi’ 2, Himantura undulata, Himantura uarnak, Maculabatis gerrardi, Pateobatis fai, Pateobatis uarnacoides, Pastinachus ater, Telatrygon biasa and Urogymnus polylepis. Distributional patterns of stingrays in South Sumatran waters are depend on species or (at least) genus level. Stingrays in South Sumatran waters are recorded from of up to more 100 km inland to the coastal zone area. Following IUCN Red List status, 10 species of stingrays are threatened with status Endangered, Vulnerable and Data Deficient; suggest the South Sumatran waters are important habitat for stingrays in Indonesia.

2022, Ocean Engineering

In the present study, a three-dimensional numerical squid model was generated from a computed tomography images of a longfin inshore squid to investigate fluid flow characteristics around the squid. The threedimensional squid model obtained from a 3D-printer was utilized in digital particle image velocimetry (DPIV) measurements to acquire velocity contours in the region of interest. Once the three-dimensional numerical squid model was validated with DPIV results, drag force and coefficient, required jet velocity to reach desired swimming velocity for the squid and propulsion efficiencies were calculated for different nozzle diameters. Besides, velocity and pressure contour plots showed the variation of velocity over the squid body and flow separation zone near the head of the squid model, respectively. The study revealed that viscous drag was nearly two times larger than the pressure drag for the squid's Reynolds numbers of 442500, 949900 and 1510400. It was also found that the propulsion efficiency increases by 20% when the nozzle diameter of a squid was enlarged from 1 cm to 2 cm.

2022

1. K.R. Anthony, P.V. Ridd, A.R. Orpin, P. Larcombe and J. Lough. “Temporal variation of light availability in coastal benthic habitats: Effects of clouds, turbidity, and tides,” Limnology and Oceanography, 49(6), pp.2201-2211. 2004. 2. J. Senko, "Sustaining Small-Scale Fisheries: Ecological, Social, and Policy Challenges and Solutions." Order No. 3738953, Arizona State University, Ann Arbor, 2015. 3. C. Kelley, A. Krolick, L. Brunner, A. Burklund, D. Kahn, W. Ball, and M. Weber-Shirk, “An Affordable Open-Source Turbidimeter,” Sensors, vol. 14, no. 4, pp. 7142–7155, Apr. 2014. Light-based bycatch reduction technology relies on light transmission through turbid marine environments. The causes of turbidity vary across marine environments, therefore, different wavelengths may be better suited for a given environment[1]. This study seeks to find the relationships between turbidity, wavelength and transmittance to inform effective bycatch reduction technology.

2022, Ocean & Coastal Management

Recent studies have demonstrated that elasmobranchs (i.e. sharks, skates and rays) are sensitive and often deterred by electrosensory stimuli (e.g. permanent magnets and electropositive metals). These studies have, however, produced mixed results; but due to the importance of reducing elasmobranch bycatch in fisheries and/or directed shark capture in beach nets, future research on electrosensory repellents is imperative. At the same time, understanding the potential influence of these materials on other marine animals is equally important so that the techniques may be selectively applied to achieve conservation goals while having little impact on non-target species. In the present study, both bait and barrier experiments were conducted in the Bahamas to assess how barium-ferrite (BaFe 12 O 19) permanent magnets might influence teleost and elasmobranch behavior. For both the bait and barrier experiments, teleost species exhibited no significant associations between behavior and treatment type. Furthermore, elasmobranchs exhibited significant behavioral variation towards magnetically-treated baits, in comparison to baited controls and procedural controls. However, during the barrier experiment blacknose sharks (Carcharhinus acronotus) and southern stingrays (Dasyatis americana) exhibited no significant behavioral changes to magnetically-treated barrier regions, whereas Caribbean reef (Carcharhinus perezi) and nurse (Ginglymostoma cirratum) sharks did. This study is the first large-scale analysis of teleost behavior around magnetically-treated baits and barriers, and provides further support to the hypothesis suggesting that electrosensory repellents target and observably alter the behavior of aquatic organisms containing electroreceptors. In addition, the species-specificity of elasmobranch responses which occurred during the barrier experiment provides valuable information for future conservation engineering applications in fishing gears and beach nets.

2022, Global Ecology and Conservation

Magnetic deterrents have recently been employed to assess their ability to reduce elasmobranch mortality in beach nets. With previous studies exhibiting promise, the present study examined the ability of a magnetic barrier technology, known as the Sharksafe Barrier, to exclude bull sharks (Carcharhinus leucas) from bait, and how behavioral interactions may change with variations in environmental and biological factors. Generalized linear mixed model analyses based on 114, 30-min trials illustrate that all interacting C. leucas were successfully excluded from baited procedural control and magnetic regions (i.e. zero entrances through either region). Avoidance and pass around frequencies significantly differed from the control region and were based on situational context. To enhance behavioral analysis techniques, an Adaptive Resolution Imaging Sonar (ARIS) was employed which revealed that C. leucas distance from and swim speed associated with the magnetic barrier region were significantly greater than those associated with the procedural control region. This study demonstrates the Sharksafe barrier's effectiveness in excluding C. leucas from baited regions, regardless of variations in biological and/or environmental parameters. While other bather protection systems (e.g. beach nets and drumlines) continue to be used, this study exhibits promise that the Sharksafe barrier can be an eco-friendly alternative to beach nets.

2022, Ocean & Coastal Management

2022, Fisheries Research

Underwater video recording of the behavior of longfin inshore squid (Doryteuthis pealeii) in response to a Nordmøre-style finfish bycatch reduction grid installed in the extension of a trawl was made during experimental fishing in Nantucket Sound off Cape Cod, Massachusetts, USA. Swimming and jetting behavior, time in trawl extension, position, and orientation of squid were quantified in relation to capture by, or escape from, the trawl. Squid actively avoided the grid and escaped by jetting and changing directions. Few squid became stuck on the grid (6.4%), the majority of which eventually passed between the grid spacings and entered the codend (83.9%). Squid that passed through the grid spent less time before the grid, and were less likely to jet or change directions (p < 0.05). Squid that approached the grid from the top of the extension, and with mantle oriented toward the grid, were more likely to be caught (p < 0.05). The potential for taking advantage of these behaviors in response to a grid is discussed in relation to improving techniques for separating squid from finfish bycatch in the squid trawl fishery.

2022, Ocean & Coastal Management

Beach nets are protective nets used to minimize interactions between potentially dangerous sharks and beachgoers. Studies have demonstrated that beach nets are substantial contributors to elasmobranch mortality. One hypothesized solution to reducing this mortality is the use of permanent magnets. The present study examined the effects of grade C8 barium-ferrite (BaFe 12 O 19) permanent magnets on bull shark (Carcharhinus leucas) behavior, a species frequently entangled in beach nets. To examine this effect, two experiments were conducted: bait and barrier experiments. Log-linear models, more specifically, Poisson regressions were used to test hypotheses pertaining to the effects of treatment type, conspecific density, water visibility, and year on shark behavior. For the bait experiment, the magnetic treatment significantly reduced feeding frequency and increased avoidance frequency, with Poisson regressions also demonstrating that conspecific density was a significant predicator of avoidance and feeding frequencies. For the barrier experiment, the magnetic treatment reduced entrance frequency and yielded an increased avoidance frequency, with Poisson regressions also demonstrating that water visibility was inversely correlated to entrance frequency. This study is the first to demonstrate that C. leucas can be deterred by permanent magnets and that magnet efficacy can vary based on situational context. While this study sheds light on the potential for permanent magnets as devices that may reduce C. leucas encounters with protective beach nets, research on magnet exclusion properties should be conducted prior to applying this concept to future shark exclusion technologies.

2022, Conservation Physiology

2022, Physiological and Biochemical Zoology

Visual temporal resolution and scotopic spectral sensitivity of three coastal shark species (bonnethead Sphyrna tiburo, scalloped hammerhead Sphyrna lewini, and blacknose shark Carcharhinus acronotus) were investigated by electroretinogram. Temporal resolution was quantified under photopic and scotopic conditions using response waveform dynamics and maximum critical flicker-fusion frequency (CFF). Photopic CFF max was significantly higher than scotopic CFF max in all species. The bonnethead had the shortest photoreceptor response latency time (23.5 ms) and the highest CFF max (31 Hz), suggesting that its eyes are adapted for a bright photic environment. In contrast, the blacknose had the longest response latency time (34.8 ms) and lowest CFF max (16 Hz), indicating its eyes are adapted for a dimmer environment or nocturnal lifestyle. Scotopic spectral sensitivity revealed maximum peaks (480 nm) in the bonnethead and blacknose sharks that correlated with environmental spectra measured during twilight, which is a biologically relevant period of heightened predation.

2022, Journal of Experimental Biology

SUMMARYSeveral factors that influence the evolution of the unusual head morphology of hammerhead sharks (family Sphyrnidae) are proposed but few are empirically tested. In this study we tested the ‘enhanced binocular field’ hypothesis (that proposes enhanced frontal binocularity) by comparison of the visual fields of three hammerhead species: the bonnethead shark, Sphyrna tiburo, the scalloped hammerhead shark, Sphyrna lewini, and the winghead shark, Eusphyra blochii, with that of two carcharhinid species: the lemon shark, Negaprion brevirostris, and the blacknose shark, Carcharhinus acronotus. Additionally, eye rotation and head yaw were quantified to determine if species compensate for large blind areas anterior to the head. The winghead shark possessed the largest anterior binocular overlap (48 deg.) and was nearly four times larger than that of the lemon (10 deg.) and blacknose (11 deg.) sharks. The binocular overlap in the scalloped hammerhead sharks (34 deg.) was greater than ...

2022, Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Longline fishing is the most common elasmobranch capture method around the world, yet the physiological consequences of this technique are poorly understood. To quantify the sub-lethal effects of longline capture in the commonly exploited Caribbean reef shark (Carcharhinus perezi), 37 individuals were captured using standard, mid-water longlines. Hook timers provided hooking duration to the nearest minute. Once sharks were landed, blood samples were taken and used to measure a suite of physiological parameters. Control data were obtained by sampling an additional three unrestrained Caribbean reef sharks underwater at an established shark feeding site. The greatest level of physiological disruption occurred after 120-180 min of hooking, whereas sharks exposed to minimal and maximal hook durations exhibited the least disturbed blood chemistry. Significant relationships were established between hooking duration and blood pH, pCO 2 , lactate, glucose, plasma calcium and plasma potassium. Longline capture appears more benign than other methods assessed to date, causing a shift in the stress response from acute at the onset of capture to a sub-acute regime as the capture event progresses, apparently facilitating a degree of physiological recovery. Continued investigation into the physiological response of elasmobranchs to longline capture is vital for the effective management of such fisheries.