What do you mean by responsible? Do you want to know the genetics behind it, what the surface markers do, or why they are metically important? I think I can help.
Answer:
your answer is segmented body and exskostkeloton
Explanation:
I have did that question and got it right but the reasons why are there body is segmented in the ground and the exoskeleton is they don't have no skeleton except in there heads gl
A a lot cause the moon control the wave of the ocean
They have 46 chromosomes :)