Morphological observations and molecular confirmation of larvae ofLevisquilla inermis(Crustacea: Stomatopoda) from the Seto Inland Sea

Abstract

Mantis shrimps are commercially important crustaceans in many areas of the world. In contrast to the relatively common studies of adults, limited studies have been attempted of larvae because of a lack of identification keys. The objectives of this study were two-fold: (1) to link wild-caught larval specimens from the Seto Inland Sea to a certain species and (2) to present a detailed morphological description of the last larval stage. The resulting molecular phylogenetic tree based on 16S rRNA gene sequences strongly implies that our larval specimens were linked to Levisquilla inermis, which was barcoded from a newly collected adult specimen with a morphological identification. K2P genetic divergence was found to be 0% among the larval and adult specimens. The congeneric species L. jurichi was the sister group of the L. inermis cluster, but the K2P distance between them was 3.4%, and it was considered a distinct species. Morphological observations provided five major distinguishing characteristics of the last-stage larva of L. inermis: (1) propodus of second maxilliped with three basal spines, (2) all five pleopods possessing an appendix interna with cincinnuli, (3) exopod of uropod longer than the endopod, (4) distal margin of the exopod of the uropod reaching the lateral tooth of telson, and (5) telson with nine intermediate denticles. Overall, our results reveal the importance of combining molecular and morphological analyses for solving stomatopod larval identification. This finding can be used to support and facilitate future research on the taxonomy and biodiversity of stomatopod larvae.