DOCSLIB.ORG

The Shark's Electric Sense

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Shark's Electric Sense BIOLOGY CREDIT © 2007 SCIENTIFIC AMERICAN, INC. LEMON SHARK chomps down on an unlucky fish. THE SHARK’S SENSE An astonishingly sensitive detector of electric fields helps sharks zero in on prey By R. Douglas Fields menacing fin pierced the surface such as those animal cells produce when in KEY CONCEPTS and sliced toward us. A great blue contact with seawater. But how they use ■ Sharks and related fish can shark—three meters in length— that unique sense had yet to be proved. We sense the extremely weak homed in on the scent of blood like a torpe- were on that boat to find out. electric fields emitted by animals in the surrounding do. As my wife, Melanie, and I watched sev- Until the 1970s, scientists did not even water, an ability few other eral large sharks circle our seven-meter Bos- suspect that sharks could perceive weak organisms possess. ton Whaler, a silver-blue snout suddenly electric fields. Today we know that such elec- ■ This ability is made possible thrust through a square cutout in the boat troreception helps the fish find food and can by unique electrosensory deck. “Look out!” Melanie shouted. We operate even when environmental condi- structures called ampullae both recoiled instinctively, but we were in tions render the five common senses—sight, of Lorenzini, after the 17th- no real danger. The shark flashed a jagged smell, taste, touch, hearing—all but useless. century anatomist who first smile of ivory saw teeth and then slipped It works in turbid water, total darkness and described them. back into the sea. even when prey hide beneath the sand. ■ The author and his colleagues We had drawn the sharks by ladling My research colleagues and I are now ex- have demonstrated that blood into the ocean, but we were not inter- ploring the molecular basis for this ability, sharks use this “sixth sense” to home in on prey during ested in their well-known attraction to while others pursue such questions as how the final phase of an attack. blood. Rather we were investigating the the sensing organ forms during develop- Other potential uses for hunters’ mysterious “sixth sense.” Labora- ment and whether our own vertebrate an- electroreceptors remain to tory research had demonstrated that sharks cestors once could detect electric fields be- be determined. CREDIT can sense extremely weak electric fields— fore they left the sea. All this work is still —The Editors www.SciAm.com SCIENTIFIC AMERICAN 75 © 2007 SCIENTIFIC AMERICAN, INC. ELECTROSENSORS IN ACTION Pore MAKO SHARK Nerve Brain Sharks and related species sense extremely weak electric fields gener- Ampullae of ated by other animals in seawater thanks Lorenzini to hundreds or even thousands of specialized ●a detectors in their snouts called ampullae of Lorenzini (a). The fields conduct electricity in well- Pore insulated, gel-filled canals (b) that extend from the skin pores to the bulb-shaped ampullae (c) lined with a single layer of sensing cells (d). Those cells, which respond to very slight changes in the electrical charge of the gel in the canal, in turn activate nearby nerves, which inform the brain of the field’s presence. quite preliminary, though. Here I describe how The pores’ purpose started to become clear in investigators first discovered electroreception in the middle of the 19th century, when researchers sharks and how we demonstrated its importance began to glean the function of the so-called lat- to successful hunting—a fascinating, little- eral line, an organ that shares some similarities known tale that spans centuries. with Lorenzini’s pore-and-tube system. The lat- eral line, a stripe extending down the sides of Hidden Sense many fish and amphibians from gills to tail, de- The story begins in 1678, when Italian anatomist tects water displacement. In fish, it consists of a Stefano Lorenzini described pores that speckled specialized row of perforated scales, each of the forward part of the head of sharks and rays, which opens into a tube lying lengthwise just un- ) MILLIONTH endowing them with something resembling a der the skin. At swellings along the length, spe- bad five-o’clock shadow. He noted that the pores cialized sensory cells called hair cells extend slen- OF A VOLT concentrated around a shark’s mouth and found der, brushlike projections (or cilia) into the tube. ACROSS A that if he peeled back the neighboring skin, each Slight water movements, such as those caused by CENTIMETER opening led to a long transparent tube that was fish swimming a few feet away, bend the micro- OF SEAWATER filled with a crystalline gel. Some of the tubes scopic hair masses like wind-driven waves rip- were small and delicate, but others were nearly pling through a field of grain. This reaction ex- photographillustrationsnoutsharkand mako of can be distinguished by a the diameter of a strand of spaghetti and several cites nerves, whose impulses inform the brain shark. This is equivalent to inches in length. Deep within the head, Lorenzi- about the strength and direction of the water dis- a voltage gradient created ni discovered, the tubes congregated in several placement. We retain the descendant of this lat- );AMADEO BACHAR( by a 1.5-volt AA battery large masses of clear jelly. He considered and eral line in our ear cochlea. then rejected the possibility that these pores were By the late 19th century the newly improved with one pole dipped in the source of fish body slime. Later, he speculat- microscope revealed that the pores on a shark’s precedingpages the Long Island Sound and ed that the pores might have another, “more hid- snout and the unusual structures underneath the other pole in waters den function,” but their true purpose remained them, today called ampullae of Lorenzini, must off Jacksonville, Fla. unexplained for hundreds of years afterward. be sensory organs of some kind. Each tube was BRANDON( COLE 76 SCIENTIFIC AMERICAN August 20 07 © 2007 SCIENTIFIC AMERICAN, INC. ELECTROSENSORS IN ACTION A sensing cell reacts when an external electric field produc- es a small electric potential across its membrane, leading channels to allow positively charged calcium ions to rush in. The influx of positive charge causes the cell to release neurotransmitters at synapses, or contact points, with nerves to the brain, stimulating them to fire. The firing rate indicates the strength and polarity of the external field, and the field’s location relative to the shark is thought to be determined by the positions of the activated pores on its body. The cells return to their original electrical state after- TIMELINE: ward by opening a second type of membrane channel that UNDERSTANDING permits positively charged potassium ions to exit. ELECTRORECEPTION 1678: Italian anatomist Stefano Calcium ions Potassium ions Lorenzini describes the structure c ● (Ca++) flow in (K+) flow out of the electroreception system of Cilium sharks and rays. Its function remains a mystery. Late 1800s: Scientists explain the function of fish’s lateral line, an organ that detects water displacement ●d and in some ways resembles the elec- Nerve ●b troreception system. Examination with microscopes delineates the details of what soon become known as ampullae Ampullae of Lorenzini Nerve of Lorenzini. External pore Support cell Gel-filled canal in skin Sensing cell Synapse 1909: G. H. Parker finds that the ampullae respond to touch. He speculates that they might sense seen to end in a bulbous pouch, or ampulla. A haps water pressure, but he could not be sure. Af- water motion. thin nerve emerged from the ampulla and joined ter all, a reflex reaction to a poke in the eye does branches of the anterior lateral line nerve. Scien- not necessarily mean that eyes had evolved to 1938: Alexander Sand records tists traced these nerve fibers to the base of the perceive sudden jabs. nerve impulse output from ampullae of Lorenzini in response to various skull, where they enter the brain through the Just as microscopes had opened up new re- stimuli. He notices that they react to dorsal surface of the medulla, a destination search avenues a century before, the just-devised tiny temperature changes. characteristic of nerves that carry sensory infor- vacuum-tube amplifier advanced the study of mation into the brain. Observers discerned a brain function in the second quarter of the 20th 1950s: H. W. Lissmann and others single tiny hair cell, similar to those of the hu- century. In 1938 Alexander Sand of the Marine describe “tuberous receptors” in weak- man inner ear and of a fish’s lateral line system, Biological Association in Plymouth, England, ly electric fish that sense their own fields. The discovery adds electrorecep- inside each ampulla. The type of stimulus they succeeded in amplifying and recording nerve tion to the list of known animal senses. might detect remained unknown, however. pulses running from ampullae of Lorenzini to the brain. He saw that impulses shot down the Early 1960s: R. W. Murray finds Electroreception Confirmed nerve in a steady stream but that certain stimuli that ampullae of Lorenzini are sensi- Researchers found themselves faced with a caused the rate to increase or decrease suddenly. tive to slight salinity variations and dilemma: How could they determine the function Sand noticed, as Parker had, that the organs re- weak electric fields. of this entirely foreign sense organ? The eventu- sponded to touch or pressure, but he found that 1970s: Adrianus Kalmijn deter- al solution came down to the combination of the firing rate also rose when cooled. Indeed, the mines that in seawater animal bodies good instrumentation and a fertile imagination. ampullae were so sensitive to temperature that produce electric fields.
Load more

Recommended publications
  • A New Stingray from South Africa
    Nature Vol. 289 22 January 1981 221 A new stingray from South Africa from Alwyne Wheeler ICHTHYOLOGISTS are accustomed to the regular description of previously un­ recognized species of fishes, which if not a daily event at least happens so frequently as not to cause great comment. Previously undescribed genera are like­ wise not infrequently published, but higher categories are increasingly less common. The discovery of a new stingray, which is so different from all known rays as to require both a new family and a new suborder to accommodate its distinctive characters, is therefore a remarkable event. A recent paper by P.e. Heemstra and M.M. Smith (Ichthyological Bulletin oj the J. L.B. Smith Institute of Ichthyology 43, I; 1980) describes this most striking ray as Hexatrygon bickelli and discusses its differences from other batoid fishes. Surprisingly, this remarkable fish was not the result of some organized deep-sea fishing programme, but was found lying on the beach at Port Elizabeth. It was fresh but had suffered some loss of skin by sand abrasion on the beach, and the margins of its fins appeared desiccated in places. The way it was discovered leaves a tantalising question as to its normal habitat, but Heemstra and Smith suggest that it may live in moderately deep water of 400-1,000m. This suggestion is Ventral view of Hexatrygon bickelli supported by its general appearance (small eyes, thin black dorsal skin, f1acid an acellular jelly, while the underside is chimaeroids Rhinochimaera and snout) and the chemistry of its liver-oil. richly supplied with well developed Harriota, and there can be little doubt The classification of Hexatrygon ampullae of Lorenzini.
    [Show full text]
  • Electrosensory Pore Distribution and Feeding in the Basking Shark Cetorhinus Maximus (Lamniformes: Cetorhinidae)
    Vol. 12: 33–36, 2011 AQUATIC BIOLOGY Published online March 3 doi: 10.3354/ab00328 Aquat Biol NOTE Electrosensory pore distribution and feeding in the basking shark Cetorhinus maximus (Lamniformes: Cetorhinidae) Ryan M. Kempster*, Shaun P. Collin The UWA Oceans Institute and the School of Animal Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia ABSTRACT: The basking shark Cetorhinus maximus is the second largest fish in the world, attaining lengths of up to 10 m. Very little is known of its sensory biology, particularly in relation to its feeding behaviour. We describe the abundance and distribution of ampullary pores over the head and pro- pose that both the spacing and orientation of electrosensory pores enables C. maximus to use passive electroreception to track the diel vertical migrations of zooplankton that enable the shark to meet the energetic costs of ram filter feeding. KEY WORDS: Ampullae of Lorenzini · Electroreception · Filter feeding · Basking shark Resale or republication not permitted without written consent of the publisher INTRODUCTION shark Rhincodon typus and the megamouth shark Megachasma pelagios, which can attain lengths of up Electroreception is an ancient sensory modality that to 14 and 6 m, respectively (Compagno 1984). These 3 has evolved independently across the animal kingdom filter-feeding sharks are among the largest living in multiple groups (Scheich et al. 1986, Collin & White- marine vertebrates (Compagno 1984) and yet they are head 2004). Repeated independent evolution of elec- all able to meet their energetic costs through the con- troreception emphasises the importance of this sense sumption of tiny zooplankton.
    [Show full text]
  • The Sensory World of Bees
    June 2015 in Australia ccThehh senseeory mmiissttrryy world of bees chemaust.raci.org.au ALSO IN THIS ISSUE: • One X-ray technique better than two • Haber’s rule and toxicity • Madeira wines worth the wait The tale in the Working and sensory lives DAVE SAMMUT g sBY tin of bees 18 | Chemistry in Australia June 2015 Bees have a well-earned reputation for pollination and honey-making, but their lesser known skills in electrocommunication are just as impressive. ccording to the United Nations, ‘of Once the worker bee’s honey stomach is the 100 crop species that provide full, it returns to the hive and regurgitates the 90 per cent of the world’s food, partially modified nectar for a hive bee. The A over 70 are pollinated by bees’ hive bee ingests this material to continue the (bit.ly/1DpiRYF). It’s little wonder, then, that conversion process, then again regurgitates it bees continue to be a subject of study around into a cell of the honeycomb. During these the world. More surprising, perhaps, is that so processes, the bees also absorb water, which much remains to be learned. dehydrates the mixture. Bee-keeping (apiculture) is believed to Hive bees then beat their wings to fan the have started as far back as about 4500 years regurgitated material. As the water evaporates ago; sculptures in ancient Egypt show workers (to as little as around 10% moisture), the blowing smoke into hives as they remove sugars thicken into honey – a supersaturated honeycomb. In ancient Greece, Aristotle either hygroscopic solution of carbohydrates (plus kept and studied bees in his own hives or oils, minerals and other impurities).
    [Show full text]
  • Waveform Sensors: the Next Challenge in Biomimetic Electroreception
    International Journal of Biosensors & Bioelectronics Mini Review Open Access Waveform sensors: the next challenge in biomimetic electroreception Abstract Volume 2 Issue 6 - 2017 The interest in developing bioinspired electric sensors increased after the rising use Alejo Rodríguez Cattaneo, Angel Caputi and of electric fields as image carriers in underwater robots and medical devices using artificial electroreception (electrotomography and electric catheterism). Electric Ana Carolina Pereira Dept Neurociencias Integrativas y Computacionales, Instituto images of objects have been most often conceived as the amplitude modulation of the de Investigaciones Biológicas Clemente Estable, Uruguay local electric field on a sensory mosaic, but recent research in electric fish indicates that the evaluation of time waveform of local stimulus can increase the electrosensory Correspondence: Ana Carolina Pereira, Department of channels capacities and therefore improve discrimination and recognition of target Neurociencias Integrativas y Computacionales, Instituto de objects. This minireview deals with the present importance of developing electric Investigaciones Biológicas Clemente Estable, Av Italia 3318 sensors specifically tuned to the expected carrier waveforms to improve design of Montevideo, Uruguay, CP11600, Tel 59824871616, artificial bioinspired agents and diagnosis devices. Email [email protected] Keywords: Electroreception, Waveforms sensors Received: June 25, 2017 | Published: July 13, 2017 Introduction signal vanish when
    [Show full text]
  • Neuroethlogy NROC34 Course Goals How? Evaluation
    Course Goals Neuroethlogy NROC34 • What is neuroethology? • Prof. A. Mason – Role of basic biology – Model systems (mainly invertebrate) • e-mail: – Highly specialized organisms – [email protected] – Biomimetics – [email protected] • Primary literature and the scientific process – No textbook – subject = NROC34 – But if you really want one, there are a couple of suggestion on the • Office Hours: Friday, 1 – 4:00 pm, SW566 syllabus • Basic principles of integrative neural function • Weekly Readings: download from course webpage – More on this a bit later www.utsc.utoronto.ca/amason/courses/coursepage/syllabus2012.html NROC34 2012:1 1 NROC34 2012:1 2 How? Evaluation • Case studies of several model systems – Different kinds of questions – Different kinds of research (techniques) • Weekly readings 5% – Sensory, motor, decision-making… • Mid-term 35-45% • Selected papers each week • Final Exam 45-60% – Read before, discuss during: usually readings are challenging and “discussion” means me explaining (so • Presentation (optional) 10% don’t be discouraged) • Most topics include current work • Weekly reading marks: each week several – Take you to the leading edge of research in selected people will be selected at random to areas contribute 3 questions about the papers. NROC34 2012:1 3 NROC34 2012:1 4 1 Information Neuroethology • Who are you people? • The study of the neural mechanisms • What do you expect to learn in this course? underlying behaviour that is biologically • What previous course have you taken in: relevant to the animal performing it. – neuroscience • This encompasses many basic mechanisms – Behaviour of the nervous system. • Is this a req’d course for you? • Combines behavioural analysis and neurophysiology NROC34 2012:1 5 NROC34 2012:1 6 Neurobiology Behavioural Science • What do I mean by “integrative neural function”? • What does the nervous system do? • Ethology • Psychology – detect information in the environment – biological behaviour – abstract concepts (e.g.
    [Show full text]
  • Sensory Biology of Aquatic Animals
    Jelle Atema Richard R. Fay Arthur N. Popper William N. Tavolga Editors Sensory Biology of Aquatic Animals Springer-Verlag New York Berlin Heidelberg London Paris Tokyo JELLE ATEMA, Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA Richard R. Fay, Parmly Hearing Institute, Loyola University, Chicago, Illinois 60626, USA ARTHUR N. POPPER, Department of Zoology, University of Maryland, College Park, MD 20742, USA WILLIAM N. TAVOLGA, Mote Marine Laboratory, Sarasota, Florida 33577, USA The cover Illustration is a reproduction of Figure 13.3, p. 343 of this volume Library of Congress Cataloging-in-Publication Data Sensory biology of aquatic animals. Papers based on presentations given at an International Conference on the Sensory Biology of Aquatic Animals held, June 24-28, 1985, at the Mote Marine Laboratory in Sarasota, Fla. Bibliography: p. Includes indexes. 1. Aquatic animals—Physiology—Congresses. 2. Senses and Sensation—Congresses. I. Atema, Jelle. II. International Conference on the Sensory Biology - . of Aquatic Animals (1985 : Sarasota, Fla.) QL120.S46 1987 591.92 87-9632 © 1988 by Springer-Verlag New York Inc. x —• All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer-Verlag, 175 Fifth Avenue, New York 10010, U.S.A.), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of Information storage and retrieval, electronic adaptation, Computer Software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use of general descriptive names, trade names, trademarks, etc.
    [Show full text]
  • Color and Learn: Sharks of Massachusetts!
    COLOR AND LEARN: SHARKS OF MASSACHUSETTS! This book belongs to: WHAT IS A SHARK? Sharks are fish that have vertebrae (skeletons) made ofcartilage instead of bones. Sharks come in all different shapes, sizes, and colors. Sharks have different kinds of teeth, feeding patterns, swimming styles, and behaviors that help them to survive in all different kinds of aquatic habitats! Can you label the different parts of a shark? second dorsal fin caudal (tail) fin pelvic fin gills anal fin pectoral fin nostril mouth eye Dorsal fin There are around 500 species of sharks in the world. Massachusetts coastal waters provide ideal habitat for several kinds of Atlantic Ocean sharks that visit our waters each season! Massachusetts HOW LONG HAVE SHARKS BEEN ON EARTH? Sharks have been on Earth since before the dinosaurs! Scientists learn about early sharks by studying fossils. Shark fossils can tell us a lot about what food the shark ate, what their habitat looked like, and how they are related to other sharks. The ancient sharks on this page are extinct. Acanthodes (ah-can-tho-deez), or “spiny shark,” was the first fish to have a cartilage skeleton! Cladoselache (clay-do-sel-ah-kee) had a body and tail shaped for swimming fast. It did not have the same kind of skin that we see in modern sharks today. Stethacanthus (stef-ah-can-thus), or “anvil shark”, had a dorsal fin shaped like an ironing board! 450 370 360 200 145 60 6.5 MILLIONS OF YEARS AGO DINOSAURS EVOLVE WHAT ARE “MODERN” SHARKS? “Modern” sharks are species that have body parts (both inside and out!) that can be found on sharks living today.
    [Show full text]
  • The Shark's Electric Sense
    BIOLOGY CREDIT © 2007 SCIENTIFIC AMERICAN, INC. LEMON SHARK chomps down on an unlucky fish. THE SHARK’S SENSE An astonishingly sensitive detector of electric fields helps sharks zero in on prey By R. Douglas Fields menacing fin pierced the surface such as those animal cells produce when in KEY CONCEPTS and sliced toward us. A great blue contact with seawater. But how they use ■ Sharks and related fish can shark—three meters in length— that unique sense had yet to be proved. We sense the extremely weak homed in on the scent of blood like a torpe- were on that boat to find out. electric fields emitted by animals in the surrounding do. As my wife, Melanie, and I watched sev- Until the 1970s, scientists did not even water, an ability few other eral large sharks circle our seven-meter Bos- suspect that sharks could perceive weak organisms possess. ton Whaler, a silver-blue snout suddenly electric fields. Today we know that such elec- ■ This ability is made possible thrust through a square cutout in the boat troreception helps the fish find food and can by unique electrosensory deck. “Look out!” Melanie shouted. We operate even when environmental condi- structures called ampullae both recoiled instinctively, but we were in tions render the five common senses—sight, of Lorenzini, after the 17th- no real danger. The shark flashed a jagged smell, taste, touch, hearing—all but useless. century anatomist who first smile of ivory saw teeth and then slipped It works in turbid water, total darkness and described them. back into the sea.
    [Show full text]
  • Mechanosensory Hairs in Bumblebees (Bombus Terrestris) Detect Weak Electric Fields
    Mechanosensory hairs in bumblebees (Bombus SEE COMMENTARY terrestris) detect weak electric fields Gregory P. Suttona,1,2, Dominic Clarkea,1, Erica L. Morleya, and Daniel Roberta aSchool of Biological Sciences, University of Bristol, Bristol BS8 1TH, United Kingdom Edited by Richard W. Aldrich, The University of Texas, Austin, TX, and approved April 26, 2016 (received for review January 29, 2016) Bumblebees (Bombus terrestris) use information from surrounding ecologically relevant magnitudes cause motion in both the antennae electric fields to make foraging decisions. Electroreception in air, a and body hairs, but only hair motion elicits a commensurate neural nonconductive medium, is a recently discovered sensory capacity of response. From these data we conclude that hairs are used by insects, yet the sensory mechanisms remain elusive. Here, we inves- bumblebees to detect electric fields. tigate two putative electric field sensors: antennae and mechanosen- sory hairs. Examining their mechanical and neural response, we Results show that electric fields cause deflections in both antennae and hairs. Bumblebee Hairs and Antennae Mechanically Respond to Electric Hairs respond with a greater median velocity, displacement, and Fields. The motion of the antennae and sensory hairs in response angular displacement than antennae. Extracellular recordings from to applied electric fields was measured by using a laser Doppler the antennae do not show any electrophysiological correlates to vibrometer (LDV) (Fig. 1). LDV measures the vibrational velocity these mechanical deflections. In contrast, hair deflections in response (v) of structures undergoing oscillations, which was transformed into to an electric field elicited neural activity. Mechanical deflections of displacement (x) and angular displacement (θ)(SI Results).
    [Show full text]
  • Tuberous Electroreceptors in Three Species of Gymnotoid Fish
    Journal J. comp. Physiol. 111, 171-207 (1976) of Comparative Physiology- A by Springer-Verlag 1976 Stimulus Filtering and Electroreception: Tuberous Electroreceptors in Three Species of Gymnotoid Fish Carl D. Hopkins Scripps Institution of Oceanography, Neurobiology Unit and Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla, California 92037, and Department of Ecology and Behavioral Biology, University of Minnesota, Minneapolis, Minnesota 55455", USA Received February 23, 1976 Summary. Electroreceptive neurons in the posterior branch of the anterior lateral line nerve of three species of electric fish (Gymnotoidei): Sternopygus macrurus, Eigenmannia virescens, and Apteronotus albifrons, show species- specific differences in the filtering of electrical stimuli. All of the tuberous electroreceptor fibers of an individual are tuned to the same frequency: that of the electric organ discharge (EOD) of the species, more specifically, to that of the individual. The fibers in Sternopygus are tuned to 50-150Hz; those in Eigenmannia to 250-500Hz, and those in Apteronotus to 800-1,200 Hz (Figs. 3, 5, 8). Two classes of organs in Sternopygus and Eigenmannia, P and T units, respond to sinusoidal stimuli at the unit's best frequency (BF) with a phase-locked partially-adapting (P), or tonic (sustained) (T) discharge. T-units are more sharply tuned and are more sensitive than P-units. Only one class of organs, P or partially adapting units, have been found in Apteronotus and phase-locking is less evident than it is in other species. Nerve section proximal to the recording site does not alter the tuning curves in Sternopygus (Fig. 18), but local warming and cooling of the cutaneous receptor site in both Sternopygus and Eigenmannia shifts the tuning curve to higher and lower frequencies, respectively (Fig.
    [Show full text]
  • Research Shows That Sharks Are Quite Clever 24 June 2013
    Research shows that sharks are quite clever 24 June 2013 measure and analyse the behavioural response of the sharks, using experimental manipulation and food rewards. The rewarded sharks showed an impressive learned response of finding and biting the source of the electric fields significantly more quickly and intensely than their unrewarded counterparts. They would, however, forget these learned adaptations after three weeks when experiments were repeated. It is thought these skills are adaptive and are ideally suited to a predator living in a complex, variable and unpredictable environment allowing them to adapt behaviour, ultimately improving their feeding efficiency. The full report was published in the international New behavioural research led by Cranfield journal Animal Cognition. ecological scientist's shows that, contrary to historical beliefs, sharks are quick to learn and More information: link.springer.com/article/10.1 … have good memories. 07/s10071-013-0637-8 Drs Joel Kimber and Andrew Gill, who designed and conducted the study, suggest that this type of research will help improve the status of the much- Provided by Cranfield University misunderstood sharks. This is vitally important as many species are endangered and need protection and public support, because of dramatic population declines caused by unregulated fishing. Sharks have historically been considered as relatively unintelligent predators. However, Cranfield University and the Marine Biological Association of the UK demonstrated that small- spotted catsharks (a common, sea-bed dwelling shark found around the entire British and NW European coast) possess impressively quick learning ability. They were also able to determine that the sharks possess a memory of between a day and a few weeks; significantly more than the 7-seconds that is, often incorrectly, associated with fish.
    [Show full text]
  • Mormyridae, Teleostei)
    Ethology 103, 404-420 (1997) © 1997 Blackwell Wissenschafts-Verlag, Berlin ISSN 0179-1613 Zoologisches Institut der Universitdt Regensburg, Regensburg Electrocommunication and Social Behaviour in Marcusenius senegalensis (Mormyridae, Teleostei) ANDREAS SCHEFFEL & BERND KRAMER SCHEFFEL, A. & KRAMER, B. 1997: Electrocommuncation and social behaviour in Marcusenius senegalensis (Mormyridae, Teleostei). Ethology 103, 404—420. Abstract The electric organ discharges (EODs) of Marcusenius senegalensis, a West African freshwater fish, are bipolar pulses of short duration (220 ± SE 13 µs). In males (n = 10; 10.1-13.1 cm standard length-which is around the si2e of getting mature), the duration of EOD pulses was of significantly greater variance than in females (n = 9; 9.8—12.8 cm standard length). Male EODs also showed a tendency for a longer duration than female EODs. Groups of three as well as of 14 M. senegalensis formed temporary schools in a 'naturally' equipped 720-1 tank. While swimming slowly in a loose school during their nocturnal active phase, fish discharged in irregular long—short—long inter-EOD interval patterns. Near neighbours displayed a tendency to discharge in intervals of similar duration (nearest neighbour distance < 1/2 fish length). On removal of a plastic partition that had separated a pair of fish for at least 3 days, mutual threat displays followed by fighting were observed. During threatening, the fish alternated regularly between bursts of a high discharge rate and short discharge breaks; the rate of change was 4/s. The subdominant animal in a group of two was attacked frequently and often ceased discharging when the dominant fish approached.
    [Show full text]