Functional morphology of the first pereiopod in crangonoid shrimps (Crustacea, Decapoda, Caridea, Crangonoidea)

The structural morphology of the first pereiopod (P1) in crangonoid shrimps is investigated here for the first time using scanning electron microscopy, with particular emphasis on morphological variation in the distal margin (PDM) of the occluding margin of the propodus. Results indicate that there is a high level of morphological variation in the surface ultrastructure of the PDM across the 20 studied genera, assigned to three major types; lamellar, tuberculate and simple. It is postulated that variation in PDM morphology may be explained by its function as a friction-mediated adhesion device that facilitates prey capture, such that the more intricate PDM morphologies may have evolved in response to a selective requirement for a more efficient prey capture device in certain crangonid lineages. Further, comparison with Glyphocrangon indicates that there is no fine-scale structural evidence of homology between the prehensile P1 of Glyphocrangon and the subchelate P1 of Crangonidae.