Then why the crab choose to have legs which only can walk sidely? What's the reason behind?
2006-09-26 19:08:53 · 7 answers · asked by a V a 4 in Science & Mathematics ➔ Zoology
Spiders have more advanced hydraulics.
Now, will you answer my question too, please?
http://answers.yahoo.com/question/index?qid=20060926082449AAKXbvy&cp=3&tp=3#all-answers
2006-09-26 19:17:45 · answer #1 · answered by hott.dawg™ 6 · 0⤊ 0⤋
A crab mainly walks backward or sideways because of the position of its eyes and it is the way its legs bend and are positioned. The crab also has 10 legs. A spider has eight legs as well but has a few more set of eyes. Usually eight but some species have fewer.
2006-09-26 19:17:49 · answer #2 · answered by deltazeta_mary 5 · 0⤊ 0⤋
A spider ALWAYS has eight legs that is true. However a crab can have as few as six and as many as 10. This is not a determining factor of the species of crustaceans.
But to answer your question, it’s the same answer as to why its easiest for you to walk forward, easy to walk backwards, and hardest to walk side to side. It’s a function of the mechanics of how many joints you have, where they are located, and which direction they are pointing in.
Spiders have legs 360 degrees around their torso. Usually evenly spaced leaving room for the eyes in the front and all joints are fluid for up and down motions. This enables them to stalk and catch prey directly in front of them. Crabs on the other hand have two groups of legs at polar opposite sides of their torsos and the joints are fluid for a side to side motion. This allows them to search the ocean floor for food but even more importantly its this setup that allows them to build their holes quickly and in between tides. It also serves as an important defense mechanism.
Hope this helps.
2006-09-26 20:44:52 · answer #3 · answered by Kyle M 1 · 1⤊ 0⤋
the spider has more joints on the legs & that makes it f=more flexible?
2006-09-26 19:11:39 · answer #4 · answered by Claude 6 · 0⤊ 0⤋
spiders are relatively taller, crabs are low slung due to water pressure.
2006-09-26 22:14:01 · answer #5 · answered by thrag 4 · 0⤊ 0⤋
I think it is a natural defense mechanism related to their eyes/brain.
2006-09-26 19:10:45 · answer #6 · answered by pump_runner 2 · 0⤊ 0⤋
Why an ostrich has two wings and cannot fly?That's nature!
2006-09-26 19:54:55 · answer #7 · answered by wow 2 · 0⤊ 0⤋