Distribution and host specialization in Tetralia crabs (Crustacea : Brachyura) symbiotic with corals in the Great Barrier Reef, Australia

Coral-symbiotic crabs of the genus Tetralia were found to be host specific, discriminating between species of Acropora. Host use was found to signific antly differ from host availability in the community, suggesting some degre e of specialization between congeners. Intraspecific differences in host ut ilization were also observed between color morphs of T. nigrolineata, with dark morphs using A. gemmifera more frequently and light morphs using A. te nuis. The distributions of Tetralia species were influenced by wave exposur e and depth, with II: rubridactyla and dark morphs of T. nigrolineata almos t exclusively found in exposed, shallow habitats. The abundances of T. rubr idactyla and T. nigrolineata (both dark and light morphs) generally appear to be correlated with the abundances of their most frequently used host cor als, particularly between depths.