|Copyright: Vlad Ghiea (vlad) (26)|
|Date Taken: 2004-05-25|
|Camera: Canon 40 D|
|Photo Version: Original Version|
|Date Submitted: 2005-03-19 12:21|
|[Note Guidelines] Photographer's Note|
|The thorny skate is found in marine and brackish waters. This species is a bottom-dweller that is typically found on a variety of substrates including sand, broken shells, gravel, pebbles, and soft mud. There seems to be evidence that thorny skates can make small seasonal migrations but they generally remain in a defined home range. The thorny skates are oviparous (egg layers). Very little is known about the reproductive biology of this species. The only detailed study was conducted in the Gulf of Maine where thorny skates were found to be reproductively active year round. There is distinct pairing with embrace between the male and female. The ovaries of the female are functional on both sides but in some cases, the right seems to be more productive. The number of developing eggs in the female has ranged from 2 to 88. Once the eggs are mature and released from the ovaries, they get fertilized in the upper part of the oviduct, and get enclosed with yolk and albumen in a capsule formed by the shell gland. These capsules vary widely in size and are believed to be associated with parental body size. The capsules are light brown and have the characteristic horns on the four corners. Typically, there is only one fertilized egg found in a single capsule. These capsules are flat on one side and convex on the other. The female will often deposit eggs in sandy or muddy flats. The gestation period is unknown for this species. When the young hatch from the capsules, they are fully formed and are similar in appearance to adult specimens. Predation on the thorny skate has not been well documented. It is suspected that gray seals prey on the adults. Egg capsules have been subject to predation by halibut, goosefish, Greenland sharks, and predatory gastropods. The thorny skate is plagued by a variety of parasites that are found on the skin, in the intestinal tract, and in body cavities. There is little danger associated with the thorny skate. Unlike most stingrays, skates do not have venomous spines. Skates do have thorns that might cause injury to a person if stepped on or picked up. Due to an increasing commercial importance, declines in biomass levels, and a paucity of specific biological information, commercial harvests of thorny skates in the U.S. portion of the western North Atlantic Ocean are now prohibited. It has recently been added to the World Conservation Union (IUCN) Red list and is considered in immediate threat of becoming an endangered species. |
The photo was taken at the Biod˘me Aquarium of Montreal.
Only registered TrekNature members may rate photo notes.