Observations of the feeding behavior and growth rates of the heterotrophic dinoflagellate Polykrikos kofoidii (Polykrikaceae, Dinophyceae)

This paper describes the feeding behavior of the heterotrophic dinoflagellate Polykrikos kofoidii Chatton on Gymnodinium catenatum Graham. Polykrikos kofoidii used a nematocyst to pull the prey into its body through the posterior sulcus, finally engulfing the prey completely. We measured growth rates of P. kofoidii on diverse assemblages of dinoflagellate prey. Gymnodinium catenatum was one of the best food sources for P. kofoidii, supporting a rapid growth rate in excess of one doubling per day. This suggests that G. catenatum populations may be controlled by P. kofoidii predation in natural bloom conditions. However, P. kofoidii cannot be a potential bloom-controlling factor in all toxic dinoflagellate blooms because it is rapidly killed by at least three Alexandrium strains.