Last week I had the opportunity to visit Saurashtra coast of Gujarat. The rainy season had painted the coastal vegetation bright green. After a diminutive interaction with fisherwomen at Madhvad, I had time to stop at the dwarf vegetation of Mangrove plants close to the road. Curiosity drove me to take a closer look at the activity between the pneumatophores of the mangrove plants (Pneumatophore – A specialized respiratory root structure in certain aquatic plants). I was welcomed by small crabs having “red gloved” chelate legs.
Perisesarma bidens is a common inhabitant of the mangrove environment and commonly called as the red claw mangrove crab, mangrove crab or red crab. Technically bidens means (bi-dens) two teeth – present on the lateral sides of the carapace. They are easily distinguished from other crabs by the red to reddish orange chelates and a greenish to olive green carapace.
The red crabs are well adapted for a semi-terrestrial existence in the tough mangrove habitat. This is taken care by the presence of unique gill chambers for modified breathing which is a characteristic feature for many species under the family Sesarmidae. They are distributed well in the east and west coasts of India in the mangrove ecosystems.
Red crabs are now common in ornamental trade and because of their quick adaptation to fresh water, are preferred by aquarium keepers. In their natural habitats they are seen wandering in grass patches close to the mangroves in the intertidal areas, sometimes climbing pneumatophores or higher in the estuarine system where the salinity is less compared to the mangrove areas.
Climbing is another interesting behaviour exhibited by red crabs. The climbing is purely to overcome tidal rise occurring during high tides. Scientists and nature enthusiasts have also recorded that climbing is to avoid predation or getting immersed for longer periods. Though there are burrows created by red crabs to hide in, they are ‘nomadic’ in wandering away from their respective holes. They always like to wander freely and move towards small elevated areas.
Red crabs seem to have a strong attachment to mangroves and are totally dependent on them. They forage near the pneumatophores to feed on dead and decaying leaves and fruits of mangroves. By this role they help in the conversion of organic materials into inorganic.
Species: P. bidens
Author: (De Haan, 1835)
© Deepak Samuel, August 2013