Comparison of the mouthpart setal fringes of seven species of mud-shrimp (Crustacea : Decapoda : Thalassinidea)

A detailed description of the mouthpart morphology is provided for Axius st irhynchus Leach, Calocaris macandreae Bell, Upogebia deltaura (Leach) and U . pusilla Petagna. The distribution of setae on the mouthparts of three add itional species of thalassinidean mud-shrimp, Callianassa subterranea (Mont agu), Jaxea nocturna Nardo and U. stellata (Montagu), is also given. Partic ular attention was paid to the mouthpart setal fringes, where major differe nces were observed in setal type, inter-setal distances and inter-setule di stances. The mouthparts of the three upogebiid species examined were charac terized by plumed setae with very small intersetal distances. The mouthpart s of the other four species of thalassinidean were dominated by more robust serrate setal types. The setal screens of the upogebiids were often made u p of a single setal type, whereas those of Calocaris macandreae and Axius s tirhynchus were often comprised of a number of different setal types. The o bservations made for Callinnassa subterranea and J. nocturna fall between t hese two extremes. These differences are discussed and related to particle size selectivity during feeding and the number of different feeding modes e mployed by a particular species.