Freshwater crab Freshwater crab There are around 1,300 species of freshwater crabs, distributed throughout the tropics and subtropics, divided among eight families. They show direct development and maternal care of a small number of offspring, in contrast to marine crabs which release thousands of planktonic larvae. This limits the dispersal abilities of freshwater crabs, so they tend to be endemic to small areas. As a result, a large proportion are threatened with extinction. There are more than 1,300 described species of freshwater crabs, out of a total of 6,700 species of crabs across all environments. The total number of species of freshwater
Malacological Society of London 1942. Molluscs range in size from cephalopods such as the octopus and giant squid to microscopic gastropod snails, and the Society is concerned with some 85,000 recognised extant species, which include 23 per cent of all named marine organisms as well as molluscs living in freshwater and terrestrial habitats. It is also interested in the species (including those of the two extinct classes of molluscs) preserved as fossils, which creates a relationship with the study of geology. In association with the Oxford University Press, the Society publishes the "Journal of Molluscan Studies", previously called "Proceedings of the Malacological Society", and