This order represents the second largest order and includes 7 families and about 113 species and their most distinguishing feature is the lack of an anal fin. Most species also have a spine in front of the first dorsal fin. The majority are deep water species, and some have luminescent organs. Certain species can reach large sizes for instance the greenland shark, Somniosus microcephalus, with 7 m. Scientists assume that the most abundant species of all known sharks may be the spiny dogfish, (Squalus acanthias), the main species used for "fish & chips".The dogfishes include a great variety of small to very big sharks. Their biggest variety is in the deep water forms. While most dogfishes possess spines in front of their dorsal fins, some lack them and therefore have been put into different families in earlier years. However, all dogfishes lack an anal fin, a characteristics that is only shared by angel sharks, saw sharks and rough sharks. Dogfishes have a wide geographic and bathymetric range and are found in shallow and deep waters of all oceans. All members of this family show a ovoviviparous style of reproduction (aplacental viviparity). This family consists of 17 genera, including 65 to 70 species.
No comments:
Post a Comment