This crab was very difficult to identify. Because of the shape of its body, legs (8) and claws I am sure it is a spidercrab. This crab was sitting in the middle of a large coral block (Porites lobata) in plain sight and didn't move at all. Crabs usually hide away so I fist suspected it to be dead. But then it moved sideways after I took this photo....
I think, this might be a decorator spidercrab that has just molted. It didn't carry any concealing sponges or anemones around yet. Look at this photo of a crab with its carapace covered.
Crabs are a very diverse and numerically abundant group (there are about 45'000 species of crustaceans).
Kalipayan, Alona, Panglao island, Bohol, Philippines February 2001 and Komodo island Indonesia, 2005
Taken with a Sea and Sea Motomarine II EX , 1:2, F 22 / Nikon Coolpix 5000 in sealux housing and subtronic flash
. Copyright Teresa Zubi