Brachyuran crab diversity in natural (Pitchavaram) and artificially developed mangroves (Vellar estuary)

Abstract

The brachyuran crab diversity was studied in four stations of Pitchavaram mangroves and three stations of Vellar mangroves. A total of 38 species of brachyuran crabs was recorded in the Pitchavaram mangroves (18 species of grapsids and 8 species of ocypodids besides others), while 8 species were recorded in Vellar mangroves (5 species of grapsids and 3 species of ocypodids). The abundance of crabs also varied between the two mangrove habitats (65-82/m 2 in Pitchavaram mangroves and 27-40/m 2 in Vellar mangroves). The Pitchavaram mangrove forest has been in existence since sixteen to seventeen hundred years. In Vellar estuary, mangrove was established 13 years ago. The mangroves with vast network of roots and trunks offer a good niche for the brachyuran crabs. Due to its age and vast extent, the Pitchavaram mangrove forest has higher brachyuran crab diversity. When the mangroves were established in Vellar estuary, the mangrove-associated crabs were not present. But subsequently due to larval transport from the Pitchavaram mangroves, few species got established. Due to the above process, the remaining species may also get established. But how much time it will take? It is an interesting question worth investigating. Continuous monitoring of brachuran crab diversity may provide the answer.