Wiki Answers has some nice information the site is below, you can also research them at the library, at pet stores and an on-line search should net you some information.
http://www.crabstreetjournal.com has the largest collection of articles online. There are lots of other sites as well.
Crabs are parasitic insects and can get there for a variety of reasons. Check the related link for further information.
There are many species of crabs, and differing sizes of claws. So a definitive answer can not be given, without more information.
Crabs will eat any dead fish they can get their claws on. There isn't much they won't eat. Answers.com has a good article on the crab, and it includes information on its diet.
There are over 5000 species of Crabs in the whole world but only 4500 species are true crabs the other 500 crabs are hermit crabs which are not 'true' crabs.According to The World of Animals. by Walters, Martin & Johnson, Jinny. (Published by Parragon, 2007) 6,793 different species of crabs are known.In addition there are about 850 species of freshwater or semi-terrestrial crabs.'True' crabs are decapod crustaceans of the infraorder Brachyura, whereas hermit crabs [decapod crustaceans of the superfamily Paguroidea] are classified quite differently due to physical characteristics. They are not even closely related to 'true' crabs. For more information, see Related Links below ads...
There are about 13 species of crabs that have the ability to live on land, most of them are known as Hermit crabs, they start out in the water but eventually move to land, however thay still need water and salt around them to survive. Coenobita is the genus under which these types of crabs are classified. There is a lot of information here on wiki just doing a search here and on the net should give you the information you seek below are a couple of links to get you going.
Some types of crabs I know of are fiddler crabs, hermit crabs and horseshoe crabs.
There are various types of crabs, including blue crabs, Dungeness crabs, snow crabs, king crabs, and spider crabs. These crabs vary in size, color, habitat, and taste, offering a diverse range of options for seafood enthusiasts.
Mostly asian shore crabs, Mud crabs,Rock crabs, Donut Crabs and Spider Crabs. I believe there are no freshwater varieties.
rock crabs are type of crabs.
mud crabs, sand crabs, ghost crabs, blue swimmer.
no but they do get cancer