Comparing Distribution Patterns of Shallow Water and Deep Water Decapod Species in the Indo-Pacific (Crustacea, Decapoda)

Distribution ranges of shallow water decapod species (swimming crabs, Portunidae) and species from deep water (deep sea hermit crabs, Parapaguridae, and deep sea swimming crabs) were compared. The comparison revealed several distinct patterns within the Indo-Pacific. Indo-Polynesian or Indo-West-Pacific distribution ranges covering the entire Indian Ocean appear to be common in littoral/sublittoral species but rare in bathyal forms. Many species from both shallow and deep habitats are also distributed within these broad limits, but are not found in the northwestern Indian Ocean. In contrast to this, a well substantiated group, which includes species with different depth preferences, is restricted to either the northwestern or the western Indian Ocean. Other patterns shared are the distribution centered around the Indo-Malayan Archipelago, and insular endemism. Observed distribution patterns are discussed with regard to distribution ranges of species from other recently revised decapod taxa, and to the distribution of various benthic and pelagic groups.