Study of crabs of family hippidae (anomura: hippoidea) of Kerala Coast

Abstract- India is bestowed with a high degree of crustacean diversity including sand crabs. Sand crabs are anomuran crabs, a highly diverse group of decapod crustaceans and comes under the super family Hippoidea. Among the families under Hippoidea, the Hippidae is a small family of worldwide distribution and having three genera such as EmeritaScopoli, 1777; HippaFabricius, 1787; and Mastigochirus Miers, 1878. These fascinating anomurans contribute considerably to the secondary production of sandy littoral habitats and their life.
Present study deals with the taxonomy, spatial-temporal variations and traditional knowledge of this sand crabs of family Hippidae along Kerala coast. Samplingwere carried out for a period of one year (May 2017 to April 2018). For studying taxonomy, spatial variations and traditional knowledge one time sampling were carried out along the fifty five beaches of Kerala and for studying temporal variation monthly sampling conducted along the three beaches of Trivandrum.
Two species of sand crab in the genus Emerita namely Emerita emeritus and Emerita holthuisi were found along the Kerala coast and also observed some pecularity in their distribution. They are not distributed uniformly along the coast. Emerita holthuisi distributed all over the coast whereasEmerita emeritus showed a restricted distribution from the southern tip of Kerala to Paravanna beach of Malappuram.
They showed a notable spatial and temporal variations in their distribution, abundance and biomass. Abundance and biomass of Emerita emeritus observed more in the Trivandrum coast and less in the Ernakulam coast. Abundance and biomass of Emerita holthuisi found more in the Alleppey coast and less in the Trivandrum coast. The abundance and biomass of Emerita emeritus found more in the early months of the year and Emerita holthuisi more in the later months of the year.
Both are dominant in different period of the year. If one species found more simultaneously the other became less. Same variation is observed in the spatial distribution also. In no one beach both species are found dominant at a time. Through this study it is concluded that both species favour different beach condition and sea state. Emerita emeritus most favoured by the beaches having Steep and high wave action whereas Emerita holthuisi favoured beach having moderate slop and calm or moderate wave actions.
These sand crabs are very familiar to fisherfolk. They used this small uneconomical crab for many purposes. Its nutritional quality is scientifically proved one. They used this as an edible one and also it have many other uses such as act as an excellent feed for ducks, used as amedicine to treat continous cough in childrens, give lactating mothers to enhance milk production, used as an excellent bait and finally act as an indicator of catfish fishery.
These results indicate that sand crab is one of the potential macrofauna of our beach ecosystem and found many peculiarity in its distribution, abundance and biomass. But influencing factors about this pecuiliarity is still a mysterious. So more studies are needed to unveiling the exact reason behind this unusual trends.