Morphology of thalassinidean (Crustacea: Decapoda) mouthparts and pereiopods in relation to feeding, ecology and grooming

The morphology of the mouthparts and pereiopods of three thalassinidean mud-shrimps, Callianassa subterranea (Montagu), Jaxea nocturna Nardo and Upogebia stellata (Montagu) (Decapoda: Thalassinidea) are described. The distribution of setae is also described and related to function, in particular to feeding and grooming. The comparative morphology of the maxillipeds and pereiopods showed greatest differences between species and can be related to differences in feeding behaviour. Callianassa subterranea has mouthpart morphology and setation suitable for handling sediment particles and highly specialized pereiopods consistent with the digging activity of a deposit feeder. Upogebia stellata is the most densely setose of the three species and many of the appendages bear layered fringes of setae which are used to trap fine particles during 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 the coxa of the third maxilliped may take over the gill grooming Functions 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 used, whilst J. nocturna is much less specialized and may represent a more primitive thalassinidean form.