ANIMALS WITH JOINTED LEGS— THE ARTHROPODS 



193 



Photos by Winchester 

 Fig. 13.9. Crabs. Fiddler crabs above and hermit crab below. 



Regeneration in the crayfish is limited to the appendages and eyes. 

 If a part of an appendage is injured, the entire appendage will most 

 likely be cast off at a certain joint and replaced by regeneration. This is 

 known as autotomy. It prevents excessive bleeding from crushed and 

 mutilated portions of the appendage, for little bleeding will occur from 

 a break at a joint. There are special muscles at the joint which contract 

 and not only break off the appendage, but also close the open blood 

 spaces. 



Among the other crustaceans, the lobster is probably the most im- 

 portant economically because it is a source of delicious food. It is just 



