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Decapods

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Fimo
39761.  Fri Dec 16, 2005 6:51 am Reply with quote

Well live and learn eh? I was always under the impression that crabs had eight legs and walked sideways but according to Wikipedia, true crabs have ten legs (including the clawed ones you see) and can walk in any direction. So are they just being shifty and sidling away when I see them?

 
gerontius grumpus
39767.  Fri Dec 16, 2005 7:21 am Reply with quote

Funny, I was just about to put something up about decapods.
Crabs, lobsters, crayfish, crawfish, scampi etc. are all decapods.
They have ten large legs (including the claws) and a larger number of smaller modified legs.
The mouthparts, antennae, swimmerets and tail fan segments are all modified legs.

 
djgordy
39769.  Fri Dec 16, 2005 7:25 am Reply with quote

True crabs do have five pairs of legs. The front ones are modified into claws and so are not used for walking meaning they have eight walking legs. There are also a number of 'false crabs', such as hermit crabs, which have the a similar form but which are deficient to the tune of two in the leg deapartment.

Crabs can walk in any direction and it clearly makes sense to move in the same direction the eyes are looking. Because sideways movement is unusual amongst animals people probably notice it more. Also, when crabs meet people they probably don't want to advance towards them so they shift away but don't want to go backwards so they move sideways, as with street jiggles.

 

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