UC San Diego

Stomatopoda, otherwise known as mantis shrimp, are a diverse group of marine crustaceans with some notable features. They have enlarged second maxillipeds encompassing the raptorial claw that distinguishes them into two groups: smashers and spearers. Previous studies have focused on morphology or a few gene trees, but only recently have there been whole mitochondrial genome-based phylogenies of mantis shrimp. However, there is only a small set of mantis shrimp taxa with their mitogenomes sequenced. Nine new mitochondrial genomes were generated from genome skimming with a conserved gene order and a combined phylogenetic analysis with available data of the mitochondrial 13 protein coding genes, 12S, 16S, and nuclear 18S. Species from three out of the seven superfamilies were used in this study. Two different rooting options were used: 1) Euphausia pacifica (krill) and 2) Hemisquilla californiensis based on the current hypothesis that Hemisquilla is the sister group to the rest of Stomatopoda. The H. californiensis outgroup datasets had the same tree topology as the E. pacifica outgroup datasets with slight variation at low supported nodes. Squilloidea was found to be highly supported as monophyletic while Gonodactyloidea was non-monophyletic. The position of H. californiensis was found inside its superfamily, Gonodactyloidea, and grouped in a low supported clade containing Odontodactylus havanensis and Lysiosquillina maculata for the E. pacifica datasets. An ancestral state reconstruction was performed on the raptorial claw form to determine the evolution of one of its most characteristic features. The results exhibited spearers as the ancestral state with smashing evolving after.