Extracellular digestion in marine dinoflagellates

Abstract. Individuals of the common coastal marine dinoflagellate genus Protoperidinium have been found to perform extracellular digestion of chain-forming diatoms by means of a pseudopodial 'feeding veil'. This mechanism of feeding explains the absence of food particles in these non-photo-synthetic, thecate organisms, and seems to be an adaptation for opportunistic feeding. Among the most common dinoflagellates in coastal marine phytoplankton are members of the genus Protoperidinium Bergh. These forms, all with a well-developed cell wall (theca), lack chloroplasts, but no details are known of their nutrition. Food items have never been seen in them, whereas other non-photosynthetic, non-thecate dinoflagellates are phagotrophic and routinely con-tain visible ingested food [e.g., Gyrodinium spp., Katodinium ( = Gymnodinium