Horseshoe Crabs, Their Eco-biological Status Along the Northeast Coast of India and the Necessity for Ecological Conservation

Abstract

Horseshoe crabs Tachypleus gigas and Carcinoscorpius rotundicauda are distributed along the northeast coast of India extending from the extreme north of West Bengal through Orissa to the northern coast of Andhra Pradesh. High congregations of these animals are found along the breeding beaches of Orissa and West Bengal during full moon and new moon high tides. Both of these Indian species have significantly different breeding patterns particularly in relation to their habitat and laying of eggs. Although at times both the species inhabit the same body of water, C. rotundicauda selects mudflats of mangroves and T. gigas have the priority for sandy estuarine and creek zones for spawning.

Environmental conditions of horseshoe crabs along the Indian coast still remain free from any kind of pollution. Also there is no known commercial exploitation for the production of amebocyte lysate or bait. But the degradation and destruction of breeding beaches by excess human activities have been posing a serious threat. This is in turn affecting the breeding migration of adult pairs (in amplexus) to come ashore for breeding. Over time, it has been observed that the number of nests (identified by their concave shapes) following the high tide has been decreasing, indicating a decline in the number of breeding pairs on the beaches. By taking the example of the status of T. tridentatus in Japan, a concerted effort should be made both at the national and international levels to protect the breeding beaches of horseshoe crabs of the world and allow these precious guests to use the space as an incubator for their fertilized eggs as ever before to grow up to trilobites and swim freely to their nourishing grounds.