Grooming behaviors and setal morphology in smasher and spearer mantis shrimps (Stomatopoda)

Abstract

Grooming behaviors that decrease fouling have been documented in various animals. The result of autogrooming has been frequently documented, with the behaviors and time spent grooming being highly variable in taxa. Setae are important in removing fouling as well as optimizing sensory reception and movement in crustaceans. Mantis shrimps (Stomatopoda) are marine crustaceans that are divided into two groups (smashers and spearers) based on the morphology of their foraging appendages. While other behaviors and structures in mantis shrimps have been intensely studied (foraging, agonistic, reproduction), grooming has been studied in detail in only a few species. We studied grooming behaviors in both groups and describe the morphologies of the grooming appendages and body regions frequently groomed. Smasher and spearer mantis shrimps were predicted to have distinct grooming behaviors and morphologies of their grooming appendages because they inhabit different environments. The grooming behaviors of smasher and spearer species were recorded and described by grooming frequency and duration, grooming mechanism, and the groomed body regions being documented. The first maxillipeds, the only grooming appendage, and frequently groomed body regions (eyes, antennae, and antennules) were observed using a scanning electron microscope. Compared to spearers, smashers groom their bodies more frequently, for longer durations, have a higher density of grooming setae, and are more fouled even though they may live in habitats with less free-suspended sedimentation. Spearers could therefore be structurally better adapted with their first maxillipeds and remove environmental fouling more efficiently for their specific habitats. Compared to various other crustaceans, mantis shrimps have relatively little fouling on their appendages and have low grooming-time budgets.