Comparative morphology of the thelycum of the planktonic shrimp genus Lucifer (Crustacea : Decapoda : Luciferidae) and its significance in taxonomy

Abstract

Adult females of all seven species of Lucifer are distinguished by each thelycum including the atrium and the processes of the terminal thoracic stemite. The thelyca of all seven species are described and illustrated in detail. A key to females of Lucifer is provided for the first time. This study made it possible to distinguish between females of closely related species: L. faxoni and L. chacei, L. penicillifer and L. intermedius, and L. typus and L. orientalis. In L. chacei, the terminal thoracic stemite has a median process, which does not develop at all in the other six species. In L. penicillifer the atrium is partitioned by a central membrane, which does not develop at all in the other six species. The opening in the atrium in L. orientalis is the longest among all seven species.