I don't know where they came from, I haven't added any coral in over 6 months and I just recently seen them. I think they might be Trapezia rufopunctata but I've never had SPS, only leathers and shrooms and all my rock is over 3 years old so they didn't hitch hike on the rocks. They do like to eat Asterina starfish I've noticed. Size wise they're a lil bit bigger than a pencil eraser.
That's Lissocarcinus orbicularis. Normally they're found riding on sea cucumbers. Their diet has been reported as small molluscs & copepods and are considered harmless in a reef tank. Jeffersbooboo's observation that they eat Asterina is really surprising. Are you sure it's the same crab?
I'm positive they're the one's eating the Asterina starfish. The crabs don't move to much, but when they see an Asterina they go grab em and pull them into their caves. Thanks for the ID Leslie. I've caught 8 overall so far, I'm hoping they keep reproducing.
I took one of them into my college Biology professor and he thought Hepatus epheliticus especially since they went after my Asterina's. Do Lissocarcinus orbicularis have their eyes together or are they spaced out?
Lissocarcinus is a portunid genus. The eyes are widely spaced, the last pair of legs has a paddle-foot instead of a pointed foot (although it's not as big as in the more pelagic species), and the claws aren't that large. Hepatus is a xanthid or xanthoid crab. The eyes are close together, the last pair of legs has a pointed foot, and the claws are big & ridged along the sides.