Grooming Behavior and Morphology in the Decapod Crustacea

Many decapod crustacean species have specialized structures for grooming the body to keep it free of epizoic growth and particulate fouling. Among the decapod species examined, preening of the chemosensory antennules with the third maxillipeds was the most widespread and morphologically conservative behavior. Penaeidean, caridean, and stenopodidean shrimps possess characteristic setal brushes on the first cheliped for cleaning the chemotactile antennular flagella. Reptant species use only the third maxillipeds for grooming these flagella. Gill cleaning mechanisms vary widely: cheliped brushes, setae arising from thoracic setobranchs, setiferous thoracic epipods. Decapods use chelipeds and setal brushes at the tips of walking legs for grooming general body surfaces. This behavior is common in the Natantia (s.l.) but is poorly developed in the Brachyura. I hypothesize that epizoic growth interferes with swimming in shrimps, and it must be removed by preening. In the ambulatory Brachyura, selection pressure to remove epizoic growth may be less intense. Many decapod species that do not appear to have general body grooming specializations are nonetheless clean. A variety of mechanisms besides grooming may serve as antifouling adaptations in these species. Grooming structures have been little studied, but they may have considerable systematic value in the study of decapod phylogeny.