Use of electrosense in the feeding behavior of sturgeons

The electro-receptive lateral line system appeared early in the evolutionary history of fish.Sturgeons,members of the primitive Chondrostei group,are known for their electroreceptors(ampullae of Lorenzini)on the head,which are thought to be sensitive to weak electric fields in aquatic environments and involved in feeding,mating and migration.Here,we report the results of a set of behavioral and electrophysiological experiments designed to determine the function and characteristics of the electrosense in cultured sturgeons.The results showed Sibe-rian sturgeon(Acipenser baerii Brandt,1869)feeding striking at bio-electric fields produced by living feed-fish enclosed in a gel chamber and at the corrosion field produced by metal rods.With an electric stimulus that mim-ics the bio-electric fields produced by living prey,the relative discharge rate of electrosensory neurons in the dorsal octavolateralis nucleus(DON)was modulated by and phase-locked to sinusoidal stimulus and some units showed selectivity for dipolar direction in white sturgeon(Acipenser transmontanus Richardson,1836).This is the first study to provide the empirical evidence correlating with electrosensory behaviors and electrophysiolog-ical responses in cultured sturgeons,and suggesting that electrosense does play an innate role in feeding behav-ior of sturgeon.We believe this will have important implications for protecting sturgeons in the wild.

Morphological structure and peripheral innervation of the lateral line system in the Siberian sturgeon (Acipenser baerii)

Light and scanning electron microscopy(SEM)were used to study the epidermal lateral line system of the Si-berian sturgeon(Acipenser baerii Brandt,1869).This system consists of mechanoreceptive neuromasts,ampul-lae and the electroreceptive organ.The neuromasts are located in 5 pairs of cephalic and 1 pair of trunk canals and superficially in the middle and posterior pit lines that lie dorsomedially along the top of the skull immedi-ately adjacent to the otic ampullae field.Both canal neuromasts and pit organ superficial neuromasts have oppo-site polarized hair cells that are parallel along the axis of the canal and pit line,respectively.However,they dif-fer in both size and shape and in the density and length of the hair bundles.The ampullae are confined on the head,adjacent to the neuromast lines.The morphological structure of the ampullae in the Siberian sturgeon is similar to the ampullae in elasmobranchs and other primitive fish.Nevertheless,it has a relatively large mucus-filled ampulla,and a shorter and narrower canal leading to a small opening to the outer epidermal surface.We also present new information concerning the peripheral innervation of lateral line receptors in sturgeons.The re-ceptors of the lateral line system are innervated by 2 pairs of cranial nerves:anterior and posterior lateral line nerves.The peripheral processes of the anterior lateral line nerve form superficial ophthalmic,buccal,otic and anteroventral rami.The peripheral processes of the posterior lateral line nerve form middle,supratemporal and lateral rami.

Sound production in marbled rockfish (Sebastiscus marmoratus) and implications for fisheries

Recently,several rockfish species(genus Sebastes)have been reported to be soniferous.To determine whether an additional rockfish species produces sounds,passive acoustic recordings were analyzed from captive marbled rockfish(Sebastiscus marmoratus)during the non-spawning season.Three distinct sounds were identified based on frequency features.The common characteristics among all sounds were low frequency(below 300 Hz)and rapidly dampened pulses consisting of 3–5 acoustic energy cycles.During free-swimming conditions in the canvas tank,the fish produced voluntary sounds with lower frequencies than the disturbance sounds produced by individuals during prodding.Two types of sounds were identified in the disturbance context:one type consists of single or double pulses with two peak frequencies,and another type consists of a series of pulses with a single peak frequency.These results suggest that specific-species and behavior-associated sounds are potentially useful in passive acoustical surveys to monitor rockfish populations and distributions remotely.

Hearing characteristics of cephalopods: Modeling and environmental impact study

Cephalopods(octopus,squid and cuttlefish)are some of the most intriguing molluscs,and they represent economically important commercial marine species for fisheries.Previous studies have shown that cephalopods are sensitive to underwater particle motion,especially at low frequencies in the order of 10 Hz.The present paper deals with quantitative modeling of the statocyst system in three cephalopod species:Octopus vulgaris,Sepia officinalis and Loligo vulgaris.The octopus’s macula/statolith organ was modeled as a 2nd-order dynamic oscillator using parameter values estimated from scanning electron micrograph images.The modeling results agree reasonably well with experimental data(acceleration threshold)in the three cephalopod species.Insights made from quantitative modeling and simulating the particle motion sensing mechanism of cephalopods elucidated their underwater particle motion detection capabilities.Sensitivity to emerging environmental issues,such as low frequency noise caused by near-shore wind farms and increasing levels of carbon dioxide in the ocean,and sensitivity to sounds produced by impending landslides were investigated in octopus using the model.

Functional C1q is present in the skin mucus of Siberian sturgeon (Acipenser baerii)

The skin mucus of fish acts as the first line of self-protection against pathogens in the aquatic environment and comprises a number of innate immune components.However,the presence of the critical classical complement component C1q,which links the innate and adaptive immune systems of mammalians,has not been explored in a primitive actinopterygian fish.In this study,we report that C1q is present in the skin mucus of the Siberian sturgeon(Acipenser baerii).The skin mucus was able to inhibit the growth of Escherichia coli.The bacteriostatic activity of the skin mucus was reduced by heating and by pre-incubation with EDTA or mouse anti-human C1q antibody.We also detected C1q protein in skin mucus using the western blot procedure and isolated a cDNA that encodes the Siberian sturgeon C1qC,which had 44.7–51.4%identity with C1qCs in teleosts and tetrapods.A phylogenetic analysis revealed that Siberian sturgeon C1qC lies at the root of the actinopterygian branch and is separate from the tetrapod branch.The C1qC transcript was expressed in many tissues as well as in skin.Our data indicate that C1q is present in the skin mucus of the Siberian sturgeon to protect against water-borne bacteria,and the C1qC found in the sturgeon may represent the primitive form of teleost and tetrapod C1qCs.

Neural basis of the stress response in a pufferfish, Takifugu obscurus

When faced with danger,pufferfish react with both a fast-start escape response and inflation behavior.The neural basis of these stress responses in the pufferfish has not been described.The present study reveals that during inflation behavior,the buccal cavity expands and compresses as a pump to control the direction of water flow and draws water in and out.The inflation involves a series of major anatomical modifications of the head.The greatly enlarged first branchiostegal ray and its associated hyohyoideus abductor muscle are the key mechanisms responsible for this behavior.The nerve branch innervating the hyohyoideus abductor muscle is highly developed,and its central origin at the motor nucleus of the VIIth cranial nerve was revealed by tract-tracing using the carbocyanine dye DiI.The central connections from its origin were found to be several motor nuclei in the medulla and the spinal cord,the nuclei of cranial nerve III and IV in the mesencephalon,and the pretectalis superficialis and periventricular preoptic nuclei in the diencephalon.Both the sympathetic cells and the parvocellular part of the periventricular preoptic nucleus might play a neuro-endocrine role in the rapid movement of the buccal cavity during puffing behavior in this species of pufferfish.The central circuit revealed by this study is hypothesized to mediate the C-start escape behavior and puffing behavior.

The sensory world of fish and fisheries: Impact of human activities–An international conference to evaluate the effects of environmental changes on the sensory world of fish/aquatic animals and fisheries

This special issue of Integrative Zoology(the official journal of the International Society of Zoological Sciences and the Institute of Zoology,Chinese Academy of Sciences)is dedicated to the sensory world of fish and fisheries and the impacts of human activities.The papers in this issue are the outcome of an international conference that was held at the Institute for Marine Biosystem and Neurosciences,College of Fisheries and Life Science,Shanghai Ocean University,Shanghai,China from 29 October to 1 November 2012.The conference was generously sponsored by The Shanghai Ocean University,The University of Maryland and The University of Western Australia.

New perspectives in fish evolution and neurobiology

ulogy,Chinese Academy of Sciences,Beijing 100080,People’s Republic of Chin The papers presented in this special issue arose from a symposium that took place from 28 November to 1 December 2007 at the Shanghai Ocean University to celebrate the inauguration of the Institute for Marine Biosystem and Neurosciences.The symposium was attended by 158 people,the majority of whom were from leading universities and institutes across China.