Decapod crustacean grooming: functional morphology, adaptive value, and phylogenetic significance. In

Grooming behavior is well developed in many decapod crustaceans. Antennular grooming by the third maxillipedes is found throughout the Decapoda. Gill cleaning mechanisms are qaite variable: chelipede brushes, setiferous epipods, epipod-setobranch systems. However, microstructure of gill cleaning setae, which are equipped with digitate scale setules, is quite conservative. General body grooming, performed by serrate setal brushes on chelipedes and/or posterior pereiopods, is best developed in decapods at a natant grade of body morphology. Brachyuran crabs exhibit less body grooming and virtually no specialized body grooming structures. It is hypothesized that the fouling pressures for body grooming are more severe in natant than in replant decapods. Epizoic fouling, particularly microbial fouling, and sediment fouling have been shown r I m ans of amputation experiments to produce severe effects on olfactory hairs, gills, and i.icubated embryos within short lime periods. Grooming has been strongly suggested as an important factor in the coevolution of a rhizocephalan parasite and its anomuran host. The behavioral organization of grooming is poorly studied; the nature of stimuli promoting grooming is not understood. Grooming characters may contribute to an understanding of certain aspects of decapod phylogeny. The occurrence of specialized antennal grooming brushes in the Stenopodidea, Caridea, and Dendrobranchiata is probably not due to convergence; alternative hypotheses are proposed to explain the distribution of this grooming character. Gill cleaning and general body grooming characters support a thalassinidean origin of the Anomura; the hypothesis of brachyuran monophyly is supported by the conservative and unique gill-cleaning method of the group.