The book contains assessment of fiddler crab diversity, revealed presence of three species namely U. annulipes, U. vocans and U. dussumieri in intertidal area of Mumbai, only U. annulipes occur in greater abundance. Physiological and biochemical analysis of U. annulipes shows that, the crab could adjust to various ecological conditions by restoring to physiological and biochemical mechanisms like respiratory rates and tissue metabolites respectively. A thick population of U. annulipes at certain areas where settling of faecal matter was more. Therefore, the species can be seen as cleaning agent of that particular area confirms the important role played by the fiddler crabs in maintaining intertidal ecosystem. Therefore, the data presented in the thesis on diversity and ecology of the fiddler crabs will be helpful in knowing the effect of coastal pollution on macrobenthos in near future.