Contributions to systematics, biogeography, and larval development of porcelain crabs (Decapoda, Anomura, Porcellanidae) from the Gulf of Mexico and adjacent waters

Forty-eight described species of porcellanids grouped into eleven genera occur in the western Atlantic. After examination of over 400 new records mainly from the Gulf of Mexico and immediately adjacent waters of the Caribbean and eastern US seaboard, two undescribed species were found and the ranges of distribution for six other species were extended northward. The larval development of Pachycheles serratus was fully described and illustrated and a comparative summary of zoeal morphology was provided for members of Pachycheles. Molecular data (partial sequences of the mitochondrial 16S rRNA gene) were used to infer phylogenetic relationships within the Porcellanidae. Petrolisthes, the most speciose genus of the family was resolved into two clades as previously suggested on the basis of morphological and molecular evidence. P. violaceus (type species of the genus) was closely related to P. tridentatus, P. quadratus, P. lewisi, and P. magdalenensis. In a second clade P. armatus, P. marginatus, and P. politus were grouped together, P. rosariensis was excluded from the P. galathinus complex, which grouped P. caribensis, P. galathinus, and Parapetrolisthes tortugensis. Species of Clastotoechus were grouped closely as a monophyletic group, which raises question regarding the validity of the monotypic genus Madarateuchus. Intrageneric divergence in Megalobrachium suggested justification for the possible resurrection of Porcellanopsis. Neopisosoma was supported as a genus distinct from Pachycheles, which contained two independent lineages. The phylogeography of Petrolisthes armatus was addressed on the basis of the mitochondrial 16S rRNA gene. Three lineages were obtained with distinct geographic distributions, northern Warm-temperate, Caribbean, and eastern Pacific. Eight haplotypes were found; the most common haplotype distributed from the southern Gulf of Mexico to Venezuela. Based on the morphology of larvae, genetics, and phylogeographic evidence of divergence, the three lineages of P. armatus could be regarded as distinct species. Without question, additional genes should be examined for this group, and the search should be continued for morphological distinctions among adults and larvae. The classification of the Porcellanidae might be updated on the basis of recent findings, especially if these can be confirmed by analyses of additional taxa and genes.