Introduction

Freshwater crabs around the world
Among all the crab species in the world, as many as one-fifth are classified as primary freshwater crabs. However, one-sixth of these freshwater crabs are at risk of extinction.

Freshwater crabs largely differ from marine crabs as they spend their entire life cycle in freshwater. Also, freshwater crabs do not go through the numerous stages of metamorphosis but instead undergo direct development.

Freshwater crabs produce small number of relatively large eggs which will directly hatch into juvenile crabs. This process of direct development increases the survival rates of the crabs as it prevents free-swimming larvae from being washed into the sea. This adaptation leads to limited dispersal capacity in small geographical regions and explains why freshwater crabs are often highly endemic. Being endemic means that the species is only located in a restricted area, and hence increases its vulnerability to extinction.