Fragilidium cf mexicanum, a thecate mixotrophic dinoflagellate which is prey for and a predator on co-occurring thecate heterotrophic dinoflagellate Protoperidinium cf divergens

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 less than or equal to 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 greater than or equal to 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.