Species Composition and Diversity of Xanthoid Crabs (Decapoda: Xanthoidea) Among Dead Corals in Nhatrang Bay, South Central Vietnam

Abstract

A total of 847 xanthoid crabs were obtained from 82 dead coral samples collected in coral reefs of Nhatrang Bay during a biodiversity survey from 22 August to 22 September 2003. Areas sampled included southern and northern Mun Island, Mieu Island, Bai Bang Island, Cau Island and Tam Islan. The material consisted of 72 species among 4 families and 32 genera. Xanthidae was the most diverse and abundant family, representing 71% of all species and 92.1% of all specimens, with Chlorodiella the most dominant taxon. While the two most dominant species, Chlorodiella corallicola and C laevissima, made up only 3% of all species, they represented 54% of the total number of individuals. The Shannon index of species diversity for xanthoid crabs ranged from 2.29 to 4.21. Other indices confirm that Cau Island is the most favorable and the northern site of Mun Island the least favorable in terms of overall xanthoid diversity. The similarity of species composition among all coral reefs was about 40%. The xanthoid community structure of reef-flats among different reefs was more similar than when comparing each reef-flat with the reefslope of the same coral reefs.