Ref ID : 4866
J.M. Balczon and James R. Pratt; A Comparison of Methods for Estimating Short-Term Feeding Rates of Algivorous Ciliated Protozoa. Arch.Protistenk 146:49-58, 1995
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Several methods for estimating short-term feeding rates of the algivorous ciliated protozoa Oxytricha fallax and Trithigmostoma cucullulus were compared to determine which method was most representative of steady-state feeding rates. Algae were stained with several dyes and vital stains for use as potential trophic tracers. Only the fluorescent stain 5-(4,6-dichlorotriazin-2-yl) aminofluorescein (DTAF) was promising as a potential trophic tracer, but ciliates preferentially ingested unstained algal food particles. We also assessed the potential for using two different species of diatom algae in tracer experiments; however, the ciliates always preferentially consumed one species of diatom when presented with equal concentrations of the two species in pairwise experiments, when the taxa were of similar size. Specifically, the ciliates preferred Navicula cryptocephala when it was offered, versus Navicula trivialis and Nitzschia palea. Feeding experiments using [14C]-labelled algae were significant (p<0.05) and explained variation was high (>80%). Feeding rate estimates from these experiments were 1.14 cells/min for O. fallax and 0.18 cells/min for T. cucullulus. Feeding experiments using starved T. cucullulus yielded feeding rates which were higher than those obtained using [14C]-labelled diatoms, even at the lowest tested food concentration. Feeding rate estimated from egestion experiments (O. fallax: 0.87 cells/min, T. cucullulus: 1.08 cells/min) conflicted with estimates from the [14C]-labelled feeding experiments, and this may be due to the physiological stress placed upon the organisms during starvation. Therefore, we recommend that [14C]-labelled food be used whenever possible to minimize selectivity effects and physiological stress effects.