Crab Species-Specific Excavation and Architecture of Burrows in Restored Mangrove Habitat

Burrowing crabs are considered to be the ecosystem engineers in mangrove ecosystems because they have impact on the ecosystem functioning through bio-geochemical transformations. This process depends on the size and shape of burrows. The present study analysed architecture of burrows, constructed by crabs in a restored mangrove habitat. Fourteen crab species were found to construct the burrows of 13 different shapes with predominance of ‘I’,’J’,’L’. The burrow shape was diverse in Metopograpsus messor, followed by Austruca occidentalis, Gelasimus vocans, and A. annulipes. The burrow structural complexity was higher during summer in Avicennia or open zone. Sesarmids were larger in size than fiddlers, making the burrows of wider opening. Fiddlers were relatively smaller in size and they constructed complex burrows at vertical position, making longer and deeper burrows, in contrast to sesarmids, which formed simple burrows at horizontal position, digging shorter and shallower burrows. The sesarmids have smaller burrows without branching in mangrove zones, whereas the fiddler crabs (except Austruca variegata) have larger burrows with or without branching in open and Avicennia zones. The fiddler crabs especially Austruca occidentalis and A.annulipes have separate openings and passage for exit and entry as an adaptation against predators. The present work identified Austruca occidentalis and A. annulipes as the most potent bio-turbating crab species for restored mangrove habitats due to their efficiency in soil excavation and large sized burrows.