Rotifer-heliozoan interactions: a population growth study

AbstractWe quantified the population growth of the predatory heliozoan Actinosphaerium eichhornii fed separately four rotifer prey (Anuraeopsis fissa, Brachionus calyciflorus, Brachionus havanaensis and Plationus patulus) at three densities (0.5, 1 and 2 ind. ml−1 per day). All the four prey rotifer species were consumed by A. eichhornii. Regardless of the prey species, increasing rotifer prey density resulted in an increased population growth of the heliozoans. Higher cyst production in A. eichhornii occurred at higher prey densities on all prey species. A. fissa offered at the lower densities of 0.5–1.0 ind. ml−1 day−1 did not lead to cyst production by A. eichhornii. The predator did not survive beyond 2 days on Chlorella vulgaris alone. When cultured together with heliozoans, A. fissa, B. calyciflorus and B. havanaensis were eliminated within 4 days. However, the prey rotifer Plationus patulus continued to survive for about 10 days with heliozoans. The highest rate of population increase of heliozoans (0.91 day−1) was recorded when fed B. calyciflorus at a density of 2 ind. ml−1 day−1, while of those of prey varied from 0.30 to 0.41 day−1 when fed Chlorella vulgaris at 1 × 106 cells ml−1 day−1. We have analyzed the impact of heliozoan predation on rotifers.