Also known as Fiddler Crab, Mangrove Fiddler Crab, Porcelain Fiddler, Ring-legged Fiddler Crab.
Found in consortiums around mangroves, mud and sandy bottoms close to the entrance of their hooded burrows where they retreat to when threatened over lagoons and reefs.
They feed on benthic plankton.
Length - 2cm
Depth - High tide area
Widespread Indo-West Pacific
Males and females live in mixed burrows with each crab having it's own burrow, The burrow being a refuge from predators and at high tide as well as a source of water at low tide.
The burrows are used for mating.
Males have a large single claw, (So can only feed at half the rate of the females)while females have two small feeding claws. They feed by scraping sediment up with their claws, and transferring it to their mouths where they sift out their food from the sand which is then spat out as a small pellet of cleaned sand. These pellets cover the mudflat by the end of the low tide period. Because males have only one small, feeding claw, they feed at half the rate of the females.
Males use their large claw for fighting as well as mating by waving it around.
Like all crabs, fiddler crabs shed their shells as they grow. If they lose a leg or claw during their growth cycle they will have a new one when they moult! Also if the male loses the large claw it will grow back on the opposite side!! They hide when their new shell first arrives because it is soft to start with and so they are very vunerable. Ref: https://en.wikipedia.org/wiki/Uca_annulipes