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All sharks and rays are cartilaginous fish, contrasting with bony fishes. Many rays are adapted for feeding on the bottom. Many rays are adapted for feeding on the bottom. Guitarfishes are somewhat between sharks and rays, displaying characteristics of both (though they are classified as rays).
The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil.
Like other fish, sharks extract oxygen from seawater as it passes over their gills. Unlike other fish, shark gill slits are not covered, but lie in a row behind the head. A modified slit called a spiracle lies just behind the eye, which assists the shark with taking in water during respiration and plays a major role in bottom–dwelling sharks.
Radakov estimated herring schools in the North Atlantic can occupy up to 4.8 cubic kilometres (1.2 cubic miles) with fish densities between 0.5 and 1.0 fish/cubic metre (3 ⁄ 8 to 3 ⁄ 4 fish per cubic yard), totalling about three billion fish in a single school. [10] These schools move along coastlines and traverse the open oceans.
Shark Anatomy (50693674756) The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. In the shark anatomy image, it depicts the beginning half of the shark, including the gills. The shark gills are especially important and were evolved from the chordate pharyngeal gill slits synapomorphy.
The basking shark (Cetorhinus maximus) is the second-largest living shark and fish, [4] after the whale shark. It is one of three plankton-eating shark species, along with the whale shark and megamouth shark. Typically, basking sharks reach 7.9 m (26 ft) in length.
A spiracle is a small hole found behind each eye. These can be tiny and circular, such as found on the nurse shark (Ginglymostoma cirratum), to extended and slit-like, such as found on the wobbegongs (Orectolobidae). Many larger, pelagic species, such as the mackerel sharks (Lamnidae) and the thresher sharks (Alopiidae), no longer possess them.
They detect small differences in electric potential between their two ends. Ampullae of Lorenzini ( sg. : ampulla ) are electroreceptors , sense organs able to detect electric fields. They form a network of mucus -filled pores in the skin of cartilaginous fish ( sharks , rays , and chimaeras ) and of basal bony fishes such as reedfish , [ 1 ...