The present work describes the complete larval development of Mithraculus sculptus (two zoeal stages, the megalopa) and the first crab instar from laboratory cultured material. The larval morphology is compared with other descriptions currently available for the Mithrax–Mithraculus complex: Mithraculus coryphe, M. forceps, Mithrax hispidus, M. pleuracanthus, M. spinosissimus and M. verrucosus. Although the different species of the Mithrax–Mithraculus complex display uniform morphological characters, the first zoeal stage of M. sculptus differs from other species in the setal meristics of the carapace and the number of aesthetascs of the antennule. The second zoeal stage differs in the number of aesthetascs of the antennule and the number of setae in the distal margin of the coxal endite of the maxillule. The megalopa of M. sculptus can be distinguished by the presence of 3–4 aesthetascs and a simple seta in the distal segment of the antennule. The morphological differences between the larvae from the genus Mithrax and Mithraculus are insufficient to support the separation of the two genera using adult morphology. Future studies should address in detail setal meristics.
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