Shape variation in the snapping claw of Alpheus Fabricius, 1898 (Decapoda: Alpheidae): A geometric morphometrics approach

The evolutionary success of the Alpheus snapping shrimps is linked to their snapping claws, which were considered the key innovation in the evolution of these shrimps. However, many aspects of the evolution of snapping claws remain unknown. We evaluate the degree of intra‐ and interspecific variation in the shape of the snapping claw in different snapping shrimp Alpheus species. For this, we used a geometric morphometric tool. We investigated the variation in snapping claw shape from two perspectives — interspecific variation and sexual shape dimorphism — in three species: Alpheus angulosus, A. carlae, and A. estuariensis, from three locations along the southern coast of Bahia state in northeastern Brazil. Our results revealed interspecific variation in the shape of the snapping claw among A. angulosus, A. carlae, and A. estuariensis. In addition, sexual shape dimorphism was confirmed in A. angulosus and A. carlae. However, in A. estuariensis, our results reveal sexual monomorphism in the snapping claw. Our findings highlight the importance of considering both ecological context and phylogenetic relationships when analysing the morphology of the snapping claw in Alpheus snapping shrimps. We suggest further investigations to better understand the interspecific variation and sexual dimorphism in snapping claws and their implications for the evolutionary history of these shrimps.