Dogfish sharks
The spiny dogfish, a member of the squaloid family, is recognized as one of the most abundant sharks in the North Atlantic. These sharks are characterized by their gray bodies adorned with small white spots and sharp spines located at the front edges of their dorsal fins. They typically inhabit temperate ocean waters, although they can also be found in arctic and tropical regions. Spiny dogfish are a significant food fish, with millions of pounds harvested annually.
In addition to their physical characteristics, some species of spiny dogfish possess tiny venom glands along their dorsal spines. Deepwater varieties have specialized organs that emit light, which helps them attract prey like squid while also providing camouflage from predators. Notable relatives include the bramble sharks, known for their rough, brambly skin texture and flexible skeletons, and sleeper sharks, which inhabit the cold Arctic waters and have a diet that includes seals. Overall, the spiny dogfish and its relatives exhibit a fascinating array of adaptations for survival in diverse marine environments.
Subject Terms
Spiny dogfish, or squaloid
The spiny dogfish shark are said to be the most abundant shark in North Atlantic waters. They inhabit the cold, ocean waters worldwide. The spiny dogfish are so named due to a sharp spine located at the front edge of each dorsal fin.
Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Squaliformes
Family: Squalidae
Genus: Pecoglossus
Species: Altivelis
The spiny dogfish sharks are an extremely common and popular food fish. Each year, millions of pounds (tens of millions of kilograms) of spiny dogfish sharks are caught. These fish have gray bodies with small, white spots. They are named for the sharp spines which are located along the front edges of each of their dorsal, or back, fins. Spiny dogfish sharks primarily inhabit temperate waters where there are only mild changes in the water temperature, although some are also found in arctic and tropical waters. Spiny dogfish sharks are common along the European coasts and on both the Atlantic and Pacific coasts of the United States. Some species of spiny dogfish shark have tiny venom glands located in grooves on the backs of their dorsal spines.
Many of the deepwater species have organs along the sides of their bodies which produce light. Scientists believe this light helps to attract squid, and some other prey. It is also believed that the light from the organs offsets the light filtering down from the surface and thus keeps the shark from casting a shadow beneath it. The lack of a shadow makes the shark difficult to see by bottom-feeding predators. The eyes of the deepwater species are very large and extremely light sensitive. This is necessary for the sharks, as the deep waters in which they live provide them with very little light with which to see.
Cigar sharks are another kind of spiny dogfish shark. An interesting feature of these thin sharks is their long, lower-jaw teeth. The length of these teeth allow these small sharks to approach larger animals, such as squid, and with biting and twisting motions, remove small pieces of flesh from their victims before the larger animals have time to protest.
The largest members of the spiny dogfish sharks are the sleeper sharks. These are the only species to live in the cold waters of the Arctic Ocean. Sleeper sharks have been seen gliding beneath the polar ice cap. Their diet includes seals and fish. If eaten, the flesh of the giant sleeper sharks can kill human and other mammals, such as dogs.
Another species of spiny dogfish sharks are the bramble sharks. These sharks receive their name from the small bumps which cover their skin. These bumps give the sharks' skin a rough, prickly, or brambly, texture. Bramble sharks grow to a length of nine feet (2 1/2 meters). They are noted for having very soft, pliable, or flexible, skeletons. This is due to the fact that the brambles bones are without calcium, the substance which gives bones in humans and many other animals their strength.
Species of spiny dogfish and allies or squaloids include:
Black dogfish Squalidae - Centroscyllium fabricii
Bramble shark Echinorhinidae - Echinorhinus brucus
Gulper shark Squalidae - Centrophorus granulosus
Hooktooth dogfish Squalidae - Aculeola nigra
Needle dogfish Squalidae - Centrophorus acus
Plunket shark Squalidae - Centroscymnus plunketi
Prickly shark Echinorhinidae - Echinorhinus cookie
Spiny pygmy shark Squalidae - Squaliolus laticaudus
Spiny dogfish Squalidae - Squalas acanthias