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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 1692

Anja L. Ooms-Wilms, G. Postema, and Ramesh D. Gulati; Clearance rates of bacteria by the rotifer Filinia longiseta (Ehrb.) measured using three tracers. Hydrobiologia 255/256:255-260, 1993

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The clearance rates (CRs) of bacteria by Filinia longiseta were measured at 19 degrees C, both in situ in Lake Loosdrecht and in the laboratory during summer. The tracer particles used in the field were: (1) 0.51 µm fluorescent microspheres, and (2) fluorescently labelled bacteria (FLB). A third type of tracer particle, natural [methyl-3H]-thymidine-labelled bacteria (<1.2 µm), were used as a radiotracer in a laboratory experiment. The uptake of the first two tracer-particle types was measured by microscopic examination of the rotifer guts. In the third case, the uptake of radioactivity was determined by liquid scintillation counting. The rate of uptake of the microspheres decreased 10 min after the start of the experiment, probably because the gut passage time was exceeded. Using a 5 min feeding time, the rate of uptake of microspheres was higher than that of the FLB, though the variation in the uptake in both cases was high. The ingestion rates and CRs of bacteria by F. longiseta based on the fluorescent tracers were: microspheres, 5115 bact.ind.-1 hr-1 and 0.368 µl ind.-1 hr-1; FLB, 2252 bact.ind.-1 hr-1 and 0.162 µl ind.-1 hr-1. The mean CR using the thymidine-labelled natural bacteria and a 10 min feeding time was 0.179 µl ind.-1 hr-1. Thus, the CR based on the microspheres method was twice as high as for the other two methods.