Trophic strategies and functional morphology of feeding appendages, with emphasis on setae, of Upogebia omissa and Pomatogebia operculata (Decapoda :Thalassinidea : Upogebiidae)

Although species of Upogebiidae historically have been considered filter fe eders, recent studies show that many species of this group also deposit fee d. In this study, the degrees of trophic specialization of two species of t his family, Upogebia omissa and Pomatogebia operculata, were analysed. Feed ing mechanisms, stomach contents and morphology of the feeding appendages, with emphasis on setae, were examined. U. omissa, found in sandy substrate, is a generalistic feeder while P. operculata inhabits burrows inside coral s, being more specialized in filter feeding. Only 21% of the 57 setal types described were common to both species. Setal types were clustered in three main categories: plumed, serrate and plumodenticulate. No simple setae wer e found. P. operculata has lower setal diversity, with higher ratio of plum odenticulate to serrate setal types than U. omissa. The 1st and 2nd pereiop ods have an important role in collecting food. The mouthparts have two main Functions: to brush and retain particles so that food can be transported f rom the pereiopods to the mouth. Generally in these appendages, the dactyli and basal endites are responsible for brushing particles and the meri and coxal endites for particle retention. The diversity of setal types and comp lexity of their distribution on the appendages may be related to the necess ity to select and triturate particles prior to ingestion, reflecting the di fferences in trophic strategies utilized by U. omissa and P. operculata. Se tal characters appear to be indicators of the relative importance of a spec ific feeding mode for species of this group. (C) 2000 The Linnean Society o r London.