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

The thecate heterotrophic dinoflagellate Protoperidiniurn cf.djvergens and the thecate mixotrophic dlnoflagellate Fragiljdium cf.mexicanurn feed on each other In general, F cf. mexicanurn 1s the predominant predator in this reciprocal predat~on At Initial concentration ratlos 20.4 (F, cf.rncxicanuln P cf d~vergens), both specles fed on each other, but did not seriously affect the other's population.At ratios > 0.8, P. cf. dlvergens was drastically reduced to very low concentrations, and drtive predation by F. cf.mexlcanurn on P. cf. divergens was observed.This reciprocal predation may affect our view of energy and cycllng of carbon in the planktonic community.