Larval stages of the crab Mithrax tortugae (Brachyura: Mithracidae) with comparisons between all species of Mithrax

Abstract

The postembryonic larval stages of Mithrax tortugae are described, illustrated and compared with the described zoeae of other Mithrax species. Mithrax tortugae showed morphological features in all the stages of larval development that differed from those observed in other species of Mithrax, especially M. hispidus. In the Zoea I stage, M. tortugae and M. pleuracanthus lacked the minute spine on the dorsal spine observed in M. hispidus; M. tortugae exhibited a terminal spine on the inner lobe of the coxal endite of the maxilla, which was not observed in M. hispidus or M. pleuracanthus. Also, M. tortugae exhibited furcae with spines that are not spinulated, whereas in M. hispidus and M. pleuracanthus these spines are spinulated. In the Zoea II stage, M. tortugae showed a terminal spine on the coxal endite of the maxillula, whereas in M. hispidus and M. pleuracanthus this spine is absent. In the Megalopa stage, we also observed differences in the sternal plate setation between M. tortugae and M. hispidus, where M. tortugae had eight simple setae and M. hispidus showed two simple and four plumodenticulate setae. Partial sequences of the 16S rRNA and COI genes of the parental female were analysed, providing additional evidence for species identification. Together, our analyses of larval morphology and the results of the molecular analyses reinforced recognition of the relationships among M. tortugae, M. hispidus and M. pleuracanthus.