Arrow Crab Reproduction

[SaltyReefKeeper]

How do arrow crabs reproduce? I have 2 small crabs with white sacs at the base of their bodies and 1 very large crab that appears to have the same body structure without the sac. We purchased 3 crabs and 1 died, but now we have 3 again.

[EdKruzel]

SaltyReefKeeper,
What amount of time are you referring to?
How large is the tank? Approx size of the crabs?

Arrow crabs are territorial, so three in a home aquarium is quite a success on your part already, or the down fall of two eventually.
Only time can tell that one.

They are not very reef friendly. Arrows will eat anything they can catch, and if hungry enough will tear open a coral to steal food.

As they molt it is almost always one piece and much thicker than say... a Bandit Coral, or Cleaner Shrimp.
So the dead AC that you removed might have only been its discarded old exoskeleton.
With two other AC's in the tank, (especially one being larger) the newly molted crab would seek a place to hide allowing it's new armor time to harden.

Days, weeks, or better than a month out comes the crab you thought was dead seeking food.

If they can find adequate cover that provides a good food source, you will seldom see them come out.

Good Luck
Ed

[rshimek]

Hi,

Arrow crabs reproduce by copulation followed the female brooding the eggs under her body (these will be a red or green mass, not white). After a while the eggs will hatch releasing planktonic feeding larvae which will live in the plankton for several weeks to a couple of months.

White sacs off the abdomen --- sounds like parasites (and no you can't remove them without killing the crab). Any chance you could post an image?