FEEDING PREFERENCE AND POPULATION-GROWTH OF ASPLANCHNA-BRIGHTWELLI (ROTIFERA) OFFERED 2 NON-EVASIVE PREY ROTIFERS

Population growth rates of the predatory rotifer Asplanchna brightwell i were determined at 25 degrees C using a large (Brachionus calyciflor us) and a small (Anuraeopsis fissa) rotifer prey species in three conc entrations (0.5, 0.1 and 2.0 mu g dry weight ml(-1)) and in five combi nations. The prey ingestion time by the predator was also measured. Fo r B. calyciflorus the ingestion time (22.97-8.95 s) was more than six times that of A. fissa (3.68 +/- 0.93). Regardless of prey type, the p opulation growth of Asplanchna increased with increasing food density. There was a direct correlation between densities of amictic and micti c females. The maximum rate of population growth (1.01 +/- 0.10 d(-1)) was higher at high density of A. fissa prey than that at the same den sity of B. calyciflorus. Progressive increase of A. fissa density in t he offered food combination resulted in a corresponding increase of th e predator's number. Gut content analysis of A. brightwelli revealed t hat the number of prey ingested increased with increasing prey densiti es.