denise
08-12-2008, 05:00 PM
Crabs are 10 legged, onmivorous hard shelled creatures found in all the worlds oceans. Of the 6000 species known, all have 8 walking legs, and the front pair of legs are specialized into enlarged claws. Their hard external shell, called an exoskeleton, is made up of chitin and calcium. The exoskeleton provides protection for the soft body underneath, and also support by forming joints which the muscles are attached to. Crabs breathe via their gills, which are located on their legs.
http://www.scubadiver.cc/forums/gallery/files/1/1/8/5/crabjoe_1.jpg
Photo by Joe Stillman
Crabs usually travel sideways, holding their claws out from their body. It is quite easy to determine the sex of a crab by examining the underside (folded in tail). Female crabs have a wide abdomen (to hold eggs), while males have a thin, pencil shaped flap. When they are born, baby crabs look nothing like their adult counterparts, and after a few weeks they begin moulting (metamorphosing) into a tiny crab that can swim and walk around. Through a series of further molts, the juvenile crab becomes an adult.
http://www.divetraining.net/pictures/2011_may_29_tortugas/DSC00682xcrab.jpg
For most crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness. Crabs will eat a combination, of algae, mollusks, worms, other crabs and detritus depending on what is readily available.
http://www.dayo.com/images/forum/somecrabdebbie_10.jpg
Photo by Debbie Buck
One of the most interesting and commonly seen crabs around Florida is the hermit crab. Hermit crabs look like tiny lobsters, and their soft body is often hidden inside a shell. The hermit crab does not grow its own shell, instead they use empty discarded shells from whelks as they grow larger. Hermit crabs creep around the reefs looking for potential shells, they inspect the opening with their antennae and, if it suits them, they move in. When threatened, hermit crabs withdraw into their shells and block the opening with their large claws. The end of their body is very flattened, so they wriggle down into the smallest part of the shell, and maintain a death grip inside the shell when predators threaten.
http://www.scubadiver.cc/fishid/HermitCrab.jpg
Giant hermit crab, Petrochirus diogenes, peering out from the safety of his whelk shell.
Photo by Bob Rosell
http://www.dayo.com/fishid/unidedcrustacean_1.jpg
Channel clinging crab, Mithrax spinosissimus, Boynton Ledge
This guy has alot of algae growing on his shell, used for camouflage
Photo by Robert Palmer
These crabs have a wide range across the sub-tropical western Atlantic to the Caribbean. They are common on coral reefs along the coast of South Florida, the Bahamas and the Turks and Caicos Islands.
Like many other reef creatures, they feed mainly under the cover of darkness. During the day, they hide out in the reef, under ledges and swim-throughs. They are often difficult to spot as their well decorated shells blend in very well with their surroundings.
http://www.scubadiver.cc/forums/gallery/files/1/1/7/8/losthairyclingingcrabaracely_1.jpg
Hairy clinging crab, Mithrax forceps, West Palm Beach
Photo by Aracely Rojas
http://www.dayo.com/images/forum/hermitcrabdebbie_1.jpg
Hermit Crab, West Palm Beach
Photo by Debbie Buck
http://www.scubadiver.cc/forums/gallery/files/1/1/8/5/crabjoe_1.jpg
Photo by Joe Stillman
Crabs usually travel sideways, holding their claws out from their body. It is quite easy to determine the sex of a crab by examining the underside (folded in tail). Female crabs have a wide abdomen (to hold eggs), while males have a thin, pencil shaped flap. When they are born, baby crabs look nothing like their adult counterparts, and after a few weeks they begin moulting (metamorphosing) into a tiny crab that can swim and walk around. Through a series of further molts, the juvenile crab becomes an adult.
http://www.divetraining.net/pictures/2011_may_29_tortugas/DSC00682xcrab.jpg
For most crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness. Crabs will eat a combination, of algae, mollusks, worms, other crabs and detritus depending on what is readily available.
http://www.dayo.com/images/forum/somecrabdebbie_10.jpg
Photo by Debbie Buck
One of the most interesting and commonly seen crabs around Florida is the hermit crab. Hermit crabs look like tiny lobsters, and their soft body is often hidden inside a shell. The hermit crab does not grow its own shell, instead they use empty discarded shells from whelks as they grow larger. Hermit crabs creep around the reefs looking for potential shells, they inspect the opening with their antennae and, if it suits them, they move in. When threatened, hermit crabs withdraw into their shells and block the opening with their large claws. The end of their body is very flattened, so they wriggle down into the smallest part of the shell, and maintain a death grip inside the shell when predators threaten.
http://www.scubadiver.cc/fishid/HermitCrab.jpg
Giant hermit crab, Petrochirus diogenes, peering out from the safety of his whelk shell.
Photo by Bob Rosell
http://www.dayo.com/fishid/unidedcrustacean_1.jpg
Channel clinging crab, Mithrax spinosissimus, Boynton Ledge
This guy has alot of algae growing on his shell, used for camouflage
Photo by Robert Palmer
These crabs have a wide range across the sub-tropical western Atlantic to the Caribbean. They are common on coral reefs along the coast of South Florida, the Bahamas and the Turks and Caicos Islands.
Like many other reef creatures, they feed mainly under the cover of darkness. During the day, they hide out in the reef, under ledges and swim-throughs. They are often difficult to spot as their well decorated shells blend in very well with their surroundings.
http://www.scubadiver.cc/forums/gallery/files/1/1/7/8/losthairyclingingcrabaracely_1.jpg
Hairy clinging crab, Mithrax forceps, West Palm Beach
Photo by Aracely Rojas
http://www.dayo.com/images/forum/hermitcrabdebbie_1.jpg
Hermit Crab, West Palm Beach
Photo by Debbie Buck