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 Visual adaptations in sharks, skates and rays.


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Type of Resource: text

Genre: Electronic Thesis or Dissertation

Date Issued: 2009

Publisher: Florida Atlantic University

Physical Form: electronic

Extent: xii, 144 p. : ill. (some col.)

Language(s): English

Summary: The central importance of vision to an organism is evident in the anatomical and physiological adaptations within the eye that can be correlated to the organism's behavior and ecology. The goal of this study was to perform a functional analysis of adaptations within the elasmobranch visual system. An integrative approach was used to examine morphological and physiological adaptations in several species and link these adaptations to phylogeny, locomotion, habitat, behavior and ecology. Functional aspects investigated were eye position, pupil shape, spectral sensitivity, temporal resolution, the extent of the visual field and ultimately the integration of the visual and electrosensory systems. The elasmobranch eye adapts to the light environment of its habitat. Sharks from similar habitats had similar spectral sensitivities such as the bonnethead and blacknose sharks, both maximally sensitive to blue light of 480 nm. The spectral sensitivity of the scalloped hammerhead, which lives in a different environment, was maximally sensitive to green light (530 nm). The temporal characteristics of the eye also matched habitat and lifestyle. Species experiencing variable light conditions exhibited increased critical flicker-fusion frequencies, such as the bonnethead (31 Hz) and scalloped hammerhead (27 Hz), in contrast to deeper or more nocturnal species such as the blacknose shark (18 Hz). Elasmobranch visual fields correlated to each species' lifestyle, habitat and foraging strategy. Expansive monocular views, including a 360° panoramic view in the yellow stingray, were measured in species that rely on vision for vigilance against predators.

Summary: The Atlantic stingray possessed large binocular overlaps (72°), which provided depth perception useful for tracking prey. By comparison, the frontal binocular overlaps of hammerhead species were larger than sharks with a more conventional head shape.This study quantified the range of the electrosensory system and the exte the visual field of several shark species, confirming both systems overlap around the head facilitating near seamless visual and electrosensory sensory function relevant to prey detection. The findings of this study indicate that ambient environmental light strongly influenced the function of the elasmobranch eye and that the extent of species' visual fields correlated with aspects of their morphology, locomotion and ecology.

Identifier: 427379814 (oclc), 216410 (digitool), FADT216410 (IID), fau:3434 (fedora)

Note(s): by Dawn Michelle McComb.Thesis (Ph.D.)--Florida Atlantic University, 2009.Includes bibliography.Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Subject(s): Visual discriminationChondrichthyes -- EmbryologyForm perceptionAdaptation (Biology)Aquatic animals -- Physiology

Persistent Link to This Record: http://purl.flvc.org/FAU/216410

Owner Institution: FAU



Autor: McComb, Dawn Michelle.

Fuente: http://fau.digital.flvc.org/islandora/object/fau%3A3434



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