Impact of copepod predation on the fecundity of Keratella cochlearis (Rotifera)

Copepod predation on rotifers affects the dynamics and structure of zooplankton communitites. Many experimental studies have analysed the feedine behaviour of some calanoid and cyclopoid copepod species on different rotifer prey type's. However. considerations of the impact of predation by these invertebrates on rotifer Populations have generally neglected possible additional effects of this predation through differential predation mortality between eggs, egg-bearing females and females without eggs. The present study used direct observations to describe the predatory effect of two freshwater copepod species, Lovenula alluaudi (Calanoida) and Acanthocyclops vernalis (Cyclopoida), oil egg-bearing females of the rotifer Keratella cochlearis. Both copepod species ingested Keratella eggs and egg-bearing, females. i.e. the female plus its egg. However, in the case of the calanoid copepod, there was a significantly greater probability Of Suppression of Keratella eggs after capture, including direct predation and separation of the eggs from their mothers, than of Keratella females plus attached eggs. In contrast, the probability of suppression of Keratella eggs by the cyclopoid copepod did not significantly differ from that of whole Keratella females. These results are discussed in terms of the impact of this predation pattern oil the fecundity of K. cochlearis populations in natural ecosystems. Rotifer reproduction may be regulated not only by food availability but also by copepod predation.