MORPHOLOGY OF THALASSINIDEAN (CRUSTACEA, DECAPODA) MOUTHPARTS AND PEREIOPODS IN RELATION TO FEEDING, ECOLOGY AND GROOMING

The morphology of the mouthparts and pereiopods of three thalassinidea n mud-shrimps, Callianassa subterranea (Montagu), Jaxea nocturna Nardo and Upogebia stellata (Montagu) (Decapoda: Thalassinidea) are describ ed. The distribution of setae is also described and related to functio n, in particular to feeding and grooming. The comparative morphology o f the maxillipeds and pereiopods showed greatest differences between s pecies and can be related to differences in feeding behaviour. Callian assa subterranea has mouthpart morphology and setation suitable for ha ndling sediment particles and highly specialized pereiopods consistent with the digging activity of a deposit feeder. Upogebia stellata is t he most densely setose of the three species and many of the appendages bear layered fringes of setae which are used to trap fine particles d uring suspension feeding. Jaxea nocturna appears to possess mouthpart and pereiopod setal combinations suitable for a fine sediment diet but is the least morphologically specialized species. It does not use its pereiopods in grooming behaviour. Specialized denticulate setae on th e coxa of the third maxilliped may take over the gill grooming Functio ns performed by the pereiopods of C. subterranea and U. stellata. In C . subterranea and U. stellata the feeding structures are adapted to a specific trophic mode but have features that allow other modes to be u sed, whilst J. nocturna is much less specialized and may represent a m ore primitive thalassinidean form.