Dinophysis - a planktonic dinoflagellate genus which can act both as a prey and a predator of a ciliate

Heterotrophic members of the marine plankton dinoflagellate genus Dinophysis are specialized predators, whose food includes the prostomatid ciliate Tiarina fusus. This ciliate differs from most planktonic ciliates in its ability to ingest prey of its own size including autotrophic Dinophysis spp. However, when trying to catch a heterotrophic Dinophy- sis sp., the ciliate is trapped instead by the dinoflagellate and emptied via a feeding tube (peduncle), which originates from the flagellar pore of the dinoflagellate. The specific predation on a ciliate by a heterotrophic dinoflagellate represents a new trophic link in the marine planktonic food web. The existence of colourl.ess thecate dinoflagellates in the marine pelagial has been recognized among taxo- nomists for more than a century (Gaines & Elbrachter 1987). In spite of this, few ecological studies dealing with the marine planktonic food webs have included them in the protozoan plankton even though they may make up a substantial part of the biomass of this group (Smetacek 1981). Knowledge about their trophic role in