A New Species of Ostracod (Crustacea) Associated with a Feather Star: First Report of Ostracoda from Crinoidea.

We describe Obesostoma crinophilum sp. nov. (Ostracoda: Podocopida: Paradoxostomatidae) obtained from the body surface of the feather star Antedon serrata A. H. Clark, 1908 (Crinoidea: Comatulida: Antedonidae). This is the first report of Ostracoda associated with Crinoidea. None of the highly specialized appendages and/or carapace that are related to a commensal lifestyle were observed in O . crinophilum sp. nov. Therefore, the relationship between O . crinophilum sp. nov. and A. serrata must be transient rather than obligatory. However, O . crinophilum sp. nov. has a more developed hook-like distal claw on the antenna in comparison with four previously known Obesostoma species. The relatively well-developed distal claw of the antenna in O . crinophilum sp. nov. should indicate its intimate association with feather stars, though the feeding habit is still unknown.