Ref ID : 2942
Peter L. Starkweather and John J. Gilbert; Feeding in the rotifer Brachionus calyciflorus IV. Selective feeding on tracer particles as a factor in trophic ecology and in situ technique. Verh.int.Ver.Limnol. 20:2389-2394, 1978
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Brachionus calyciflorus does appear to be able to select specific particle types from simple mixtures of suitable foods. The answer to our original proposition, which asked whether or not a single tracer particle type could be reliably used as an indicator of feeding activities on other, perhaps very different particles, would therefore appear to be no. This is certainly the case for B. calyciflorus, at least where the available cells have little similarity in either size or shape. In diverse natural particle suspensions, this problem would be accentuated, since clearance rates (or collection efficiencies) may differ for various cell types at a given density and for a single cell type at different relative densities. A single tracer cell at a single density is almost certain, therefore, to give values which are not representative of the clearance rates on the entire natural assemblage of potential foods. Of equal importance of in situ study, and of great interest for rotifer trophic ecology, is the indication from Tables 1 and 2 that feeding history affects food selectivity. For example, with yeast as the primary food, yeast-cultured animals fed on Rhodotorula preferentially wheres Euglena-cultured rotifers preferred Euglena. This remarkable difference was expressed by the rotifers even though they had acclimated in similar suspensions for at least 1 hr. The results of tracer-based in situ study of rotifer feeding may therefore be dependent upon choice of tracer type and final suspended density, animal feeding history and of course, the species under investigation. A more complete picture of community grazing, including appreciation that suspension-feeding rotifers may be selective feeders, requires the use of more than one tracer type and may be best achieved with several differentially-labeled particles covering the ranges of sizes and varieties of available natural foods.