Koh Chang Crustacean Species

Fiddler Crab (Uca tetragonon)

Image: Dave Hinchliffe

Observed: Koh Chang, 2016
Observed By:Dave Hinchliffe

A fiddler crab, sometimes known as a calling crab, may be any of approximately 100 species of semi-terrestrial marine crabs which make up the genus Uca. As members of the family Ocypodidae, fiddler crabs are most closely related to the ghost crabs of the genus Ocypode. This entire group is composed of small crabs – the largest being slightly over two inches across. Fiddler crabs are found along sea beaches and brackish inter-tidal mud flats, lagoons and swamps. Fiddler crabs are most well known for their sexually dimorphic claws; the males’ major claw is much larger than the minor claw while the females’ claws are both the same size.

…and seeing a bunch of them in mating season prancing around and jousting with each other like single males in a village disco is a very entertaining sight.

Fiddler Crab Wikipedia

Spotted Hermit Crab (Dardanus megistos)

Image Copyright BB Divers

Image copyright BB Divers

Observed: Koh Chang Reefs, 2015
Observed By: BB Divers

The hermit crab is a great opportunist. Let’s face it it’s hard work being a crab. Your shell doesn’t grow and you do – so then you have to lose the old shell and wait around for ages while your new one hardens. and in the meantime you’re not protected from all the feasting beasts of the reef.

Why not just nick one?

So the hermit crab just grabs one of the many uninhabited mollusc shells that lie around and moves in. When it gets too small simply move to a new shell. Too easy!

Spotted Hermit Crab Wikipedia