Shore to landward transect burrow diversity of fiddler crab in a tropical intertidal coast of Chittagong in Bangladesh

Mst Mansura Khan ,Md Mukhlesur Rahman Khan

doi:10.3329/ralf.v4i2.33725

Abstract

Burrows indicate the abundance and distribution of fiddler crab in an intertidal coast that varies with structure and morphology within intertidal habitats. We observed fiddler crab burrow density and characters (burrow length, depth, diameter and volume) within randomly selected six 1m2 quadrate from three intertidal habitats: higher saltmarsh, mangrove pool (a small ditch distributed within mangrove) and mangrove land through field surveys in a coast of Chittagong, Bangladesh. Burrows were observed and counted for density estimation, and burrow characteristics were studied through excavating 10 representative burrows from each quadrate of each habitat. Spearman correlation was used to relate between the distances (from shore towards land) and burrow characters. Transect starting from saltmarsh as base towards mangrove land showed burrow density decreased from shore to higher intertidal habitat. Simultaneously, higher burrow length and diameter were observed landward and contrariwise shoreward. Burrow prevalence in mangrove pools represents fiddler crabs are abundant within land and shore interface presumably due to the dual privilege of easy burrowing and moist condition required for gill ventilation.Res. Agric., Livest. Fish.4(2): 131-140, August 2017

Highlights

Fiddler crabs of the genus Uca Leach, 1814 are variably distributed over tropical to temperate mudflats, salt marshes, mangrove swamps, and sandy beaches (Crane, 1975; Hodgson, 1987; Peer, 2015)
Fiddler crab burrows were diversely distributed among three habitats in the intertidal zone, and the burrow characters differed considerably (Table 1)
Fiddler crab burrow distribution and characters differed in different habitats of the intertidal coast of Bangladesh with more burrow density in shoreward and contrariwise towards landward

Summary

Introduction

Fiddler crabs of the genus Uca Leach, 1814 are variably distributed over tropical to temperate mudflats, salt marshes, mangrove swamps, and sandy beaches (Crane, 1975; Hodgson, 1987; Peer, 2015). This genus is noteworthy with sexual dimorphism with male having one astoundingly enlarged and one minor cheliped, whereas females possess two sized chelipeds (Peer, 2015). Burrows provide a shelter and escape route from terrestrial predators during exposed at low tide and from aquatic predators during at high tide, water for physiological processes, sites for molting and reproductive needs (Hyatt and Salmon, 1979; Christy, 1982; Thurman, 1984; Christy, Backwell et al, 2001; and Milner et al, 2010)

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Discussion

Conclusion