Is my Arrow Crab Supposed to Do this?

[luconi]

My arrow crab has something below the head/body that looks swollen and white. Sometimes, it opens on something like a hinge and there's normally nothing in there. Then it closes back up and goes back to normal. It seems to be healthy. Could this be a female that is ready to lay eggs or something? Thanks! :fish2:

 

[mod0522]

That hinge like think under the crab is its 'tail' I believe. The abdomen and tail are tucked under the body, protected by the crabs carapace.

 

[AJSTITAN14]

Yes, sounds like eggs. The reproductive organs are under that flap which is a modified tail. I doubt the eggs are fertile though.