Reassessment of Heptacarpus futilirostris (Bate, 1888) with description of a new species from Japan (Decapoda: Caridea: Thoridae)

The availability of topotypic specimens of the supposedly common thorid shrimp Heptacarpus futilirostris (Bate, 1888), collected from Akashi Strait, Seto Inland Sea, Japan, by a local commercial trawler, enabled the author to establish the true identity of this species and to clarify its male characteristics, including the considerable lengthening of the third maxilliped and first pereopod. Specimens previously identified as H. futilirostris from shallow coastal waters in Japan were found to actually represent an unnamed species. The new species, Heptacarpus tectus, shares significant lengthening of the third maxilliped in adult males with H. futilirostris, but differs from the latter by the non-elongate but thickened first pereopod in the male, the less slender first pereopod in the female, better developed armature on the dorsodistal margin of the first pereopod merus, consisting of row of minute spiniform setae, and the relatively short third to fifth pereopods. The molecular phylogenetic analyses using the mitochondrial COI and 16S rRNA genes support rigorously the distinctness between the two species. References to H. futilirostris are reviewed in the light of the present findings to clarify the distribution of the two species.