Catshark
Catsharks are ground sharks of the family Scyliorhinidae. They are one of the largest families of sharks with around 160 species placed in 17 genera.[2] Although they are generally known as catsharks, some species can also be called dogfish due to previous naming.[3] However, a dogfish may generally be distinguished from a catshark as catsharks lay eggs while dogfish have live young.[3] Like most bottom feeders, catsharks feed on benthic invertebrates and smaller fish. They are not harmful to humans.[3]
Catsharks may be distinguished by their elongated, cat-like eyes and two small dorsal fins set far back. Most species are fairly small, growing no longer than 80 cm (31 in); a few, such as the nursehound (Scyliorhinus stellaris) can reach 1.6 m (5.2 ft) in length. Most of the species have a patterned appearance, ranging from stripes to patches to spots.
Characteristics of genus Apristurus are mostly dark bodies, and having a long anal fin that ends in front of where the lower caudal fin begins. The snouts of the species of Apristurus are flat. They also present upper and lower labial furrows.
The sonic hedgehog dentition expression is first found as a bilateral symmetrical pattern and is found in certain areas of the embryonic jaw.[5] Sonic hedgehog (a secreted protein that, in humans, is encoded by the SHH gene) is involved in the growth and patterning of different organs.[6] Every 18–38 days the teeth are replaced as is a common characteristic of the developmental process of sharks.
The "swell sharks" of the genus Cephaloscyllium have the curious ability to fill their stomachs with water or air when threatened, increasing their girth by a factor of one to three.
Catsharks are found around seabeds in temperate and tropical seas worldwide, ranging from very shallow intertidal waters to depths of 2,000 m (6,600 ft) or more, such as the members of genus Apristurus[10] The red-spotted catshark lives in the shallower rocky waters ranging from Peru to Chile and migrates to deeper waters during the winter.[11] They are usually restricted to small ranges. Juvenile and adult chain dogfish live on the soft or rocky bottom of the Atlantic from Massachusetts to Nicaragua. Adults tend to live on the soft, sandy bottoms possibly due to their need of egg deposition sites.[12]
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