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Journal ArticleDOI

Electroreception in juvenile scalloped hammerhead and sandbar sharks

01 Dec 2002-The Journal of Experimental Biology (The Company of Biologists Ltd)-Vol. 205, Iss: 23, pp 3609-3621
TL;DR: Although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide a greater lateral search area, which may increase the probability of prey encounter, and enhanced maneuverability, which might aid in prey capture.
Abstract: The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The ‘enhanced electroreception’ hypothesis was tested by comparing the behavioral responses of similarly sized carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead sharks Sphyrna lewini and sandbar sharks Carcharhinus plumbeus oriented to dipole electric fields from the same maximum distance (approximately 30 cm) and thus demonstrated comparable behavioral-response thresholds (<1 nV cm ‐1 ). Despite the similarity of response threshold, the orientation pathways and behaviors differed for the two species. Scalloped hammerheads typically demonstrated a pivot orientation in which the edge of the cephalofoil closest to the dipole remained stationary while the shark bent its trunk to orient to the center of the dipole. By contrast, sandbars swam in a broader arc towards the center of the dipole. The different orientation patterns are attributed to the hydrodynamic properties of the cephalofoil, which enables the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevented them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide (1) a greater lateral search area, which may increase the probability of prey encounter, and (2) enhanced maneuverability, which may aid in prey capture. Movies available on-line

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Journal ArticleDOI
TL;DR: It is concluded that nursery populations linked by continuous coastline have high connectivity, but that oceanic dispersal by females is rare, and oceanic barriers appear to have a much stronger influence on the genetic architecture of this species and may indicate a mechanism for recent evolutionary radiations in the genus Sphyrna.
Abstract: Large marine fishes typically have little population genetic structure. The exceptions are associated with sedentary behaviour, disjunct distributions, or reproductive philopatry. Scalloped hammerhead sharks (Sphyrna lewini) incorporate the contrasting traits of oceanic habitat (usually associated with high dispersal) and possible fidelity to nursery grounds (for reproductive females). To evaluate the expectations of these contrasting behaviours, we examined the global genetic structure of S. lewini based on collections (n = 271 individuals) from 20 nursery areas. A 548-bp fragment of mitochondrial DNA control region revealed 22 polymorphic sites, 24 haplotypes, and three lineages distinguished by 2.56–3.77% sequence divergence. Coalescence analyses based on a provisional molecular clock indicate an origin in the Indo-West Pacific with late Pleistocene radiations into the central Pacific (Hawaii) and eastern Pacific (Central America), as well as recent interchange between oceans via southern Africa. Population subdivisions are strong (overall ΦST = 0.749, P 10). We conclude that nursery populations linked by continuous coastline have high connectivity, but that oceanic dispersal by females is rare. Although we cannot rule out philopatry to natal nurseries, oceanic barriers appear to have a much stronger influence on the genetic architecture of this species and may indicate a mechanism for recent evolutionary radiations in the genus Sphyrna.

244 citations


Cites background from "Electroreception in juvenile scallo..."

  • ...This species, and perhaps all hammerhead sharks (Sphyrnidae), have geomagnetic orientation and navigation abilities, possibly enhanced by their unique laterally expanded head (Klimley 1993; Montgomery & Walker 2001; Kajiura & Holland 2002; Meyer et al ....

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Journal ArticleDOI
TL;DR: Confirmation of "fatty" as a taste primary will require additional studies that verify these observations are taste specific, as there is increasing anatomical, electrophysiological, animal behavior, imaging, metabolic, and psychophysical evidence that free fatty acids are detectable when non-taste cues are minimized.
Abstract: Taste is a chemical sense that aids in the detection of nutrients and guides food choice. A limited number of primary qualities comprise taste. Accumulating evidence has raised a question about whether fat should be among them. Most evidence indicates triacylglycerol is not an effective taste stimulus, though it clearly contributes sensory properties to foods by carrying flavor compounds and altering texture. However, there is increasing anatomical, electrophysiological, animal behavior, imaging, metabolic, and psychophysical evidence that free fatty acids are detectable when non-taste cues are minimized. Free fatty acids varying in saturation and chain length are detectable, suggesting the presence of multiple transduction mechanisms and/or a nonspecific mechanism in the oral cavity. However, confirmation of “fatty” as a taste primary will require additional studies that verify these observations are taste specific. Oral exposure to free fatty acids likely serves as a warning signal to discourage intake and influences lipid metabolism.

169 citations

Journal ArticleDOI
TL;DR: High-speed imaging was used to record the prey-tracking behavior of larval zebrafish as they fed upon paramecium, indicating the presence of sophisticated locomotor control circuitry in this relatively simple model organism.
Abstract: High-speed imaging was used to record the prey-tracking behavior of larval zebrafish as they fed upon paramecium. Prey tracking is comprised of a variable set of discrete locomotor movements that toge

142 citations


Cites background from "Electroreception in juvenile scallo..."

  • ...Distinct strike kinematics can arise out of morphological necessity even if the same sensory modality is used, as has been demonstrated for sphyrnid and carcharinid sharks that use electroreception to detect and approach prey [Kajiura and Holland, 2002]....

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References
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Book
31 Dec 1992
TL;DR: Sharks of the world :an annotated and illustrated catalogue of shark species known to date as mentioned in this paper, is an annotated catalogue of sharks species known in the wild and has been published for the first time.
Abstract: Sharks of the world :an annotated and illustrated catalogue of shark species known to date , Sharks of the world :an annotated and illustrated catalogue of shark species known to date , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

2,127 citations

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1,799 citations

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1,058 citations

BookDOI
01 Jan 1988-Copeia
TL;DR: This volume constitutes a series of invited chapters 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, Florida.
Abstract: This volume constitutes a series of invited chapters 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, Florida. The immediate purpose of the conference was to spark an exchange of ideas, concepts, and techniques among investigators concerned with the different sensory modalities employed by a wide variety of animal species in extracting information from the aquatic environment. By necessity, most investigators of sensory biology are specialists in one sensory system: different stimulus modalities require different methods of stimulus control and, generally, different animal models. Yet, it is clear that all sensory systems have principles in common, such as stimulus filtering by peripheral structures, tuning of receptor cells, signal-to-noise ratios, adaption and disadaptation, and effective dynamic range. Other features, such as hormonal and efferent neural control, circadian reorganization, and receptor recycling are known in some and not in other senses. The conference afforded an increased awareness of new discoveries in other sensory systems that has effectively inspired a fresh look by the various participants at their own area of specialization to see whether or not similar principles apply. This inspiration was found not only in theoretical issues, but equally in techniques and methods of approach. The myopy of sensory specialization was broken in one unexpected way by showing limitations of individual sense organs and their integration within each organism. For instance, studying vision, one generally chooses a visual animal as a model.

664 citations