Feeding by the newly described heterotrophic dinoflagellate Gyrodinium jinhaense: comparison with G. dominans and G. moestrupii

Abstract

Heterotrophic dinoflagellates are major grazers of microalgae in marine food webs. The feeding of the newly described heterotrophic dinoflagellateGyrodinium jinhaensewas explored by providing 19 common microalgal prey species and the ciliateMesodinium rubrumas prey. Furthermore, the specific growth and ingestion rates ofG. jinhaensefeeding on the chlorophyteDunaliella salinawere determined as a function of prey concentration. Cells ofG. jinhaensewere able to feed on microalgae of sizes <= 26 mu m with the exception of the dinoflagellateKarenia mikimotoi. In contrast,G. jinhaensedid not feed on microalgae > 26 mu m with the exception of the dinoflagellateLingulodinium polyedra. With increasing mean prey concentration, both the specific growth and ingestion rates ofG. jinhaensefeeding onD. salinarapidly increased at mean prey concentrations < 504 ng C mL(-1)(6300 cells mL(-1)), but slowly at higher prey concentrations. The maximum growth and ingestion rates ofG. jinhaensefeeding onD. salinawere 0.655 day(-1)and 0.82 ng C predator(-1)day(-1)(10 cells predator(-1) day(-1)), respectively.Gyrodinium dominansandG. moestrupiiare able to feed on most microalgal prey species, including the species thatG. jinhaensedid not feed on. Moreover, these twoGyrodiniumspecies have positive growth rates when feeding on the red-tide dinoflagellatesProrocentrum cordatumandScrippsiella acuminata, which did not support growth ofG. jinhaense. Therefore,G. jinhaensehas an ecological niche different from that ofG. dominansandG. moestrupii,and this pattern may be the result of evolution among theseGyrodiniumspecies.