Predation by the heterotrophic dinoflagellate Protoperidinium cf divergens on copepod eggs and early naupliar stages

Abstract

The heterotrophic dinoflagellate Protoperidinium cf. divergens, known as prey for adult copepods, itself feeds on copepod eggs and early naupliar stages. One to several P. cf. divergens can attack an egg or nauplius larger than themselves. The time for an egg to be digested was proportional to the number of P. cf. divergens attacking it. Ingestion rates of P. cf. divergens on Acartia tonsa eggs and on 100 mu m diameter unidentified eggs with a smooth surface increased linearly with increasing mean prey concentration. Estimated daily consumption of eggs by P. cf. divergens suggests that it may sometimes have a considerable predation impact on the populations of copepod eggs. This predation may change the general concept of energy and cycling of carbon in the planktonic community because the genus Protoperidinium and copepods are often amongst the most abundant micro- and macrozooplankton.