ABSTRACT: The thecate heterotrophic dinoflagellate Protoperidinium cf. divergens and the thecate mixotrophic dinoflagellate Fragilidium cf. mexicanum feed on each other. In general, F. cf. mexicanum is the predominant predator in this reciprocal predation. At initial concentration ratios <=0.4 (F. cf. mexicanum:P. cf. divergens), both species fed on each other, but did not seriously affect the other's population. At ratios >= 0.8, P. cf. divergens was drastically reduced to very low concentrations, and active predation by F. cf. mexicanum on P. cf. divergens was observed. This reciprocal predation may affect our view of energy and cycling of carbon in the planktonic community.

KEY WORDS: Dinoflagellate · Food web · Heterotrophy · Mixotrophy · Protist · Reciprocal predation

Published in MEPS Vol. 151 (1997) on May 22
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997