Parvilucifera infectans Noren et Moestrup gen. et sp nov (Perkinsozoa phylum nov.): a parasitic flagellate capable of killing toxic microalgae

The toxic dinoflagellate Dinophysis, collected on the Swedish West Coast, w as found to contain round bodies previously interpreted as the result of se xual reproduction. After two weeks of darkness in the refrigerator, all Din ophysis had died, however, and round bodies were present. These proved to b e sporangia of a parasitic protist, here named Parvilucifera infectans gen. et sp. nov. Its identity was examined by LM, EM, and DNA sequencing. It is related to Perkinsus, an oyster-killing protist, and Colpodella, a phagocy tic protist. Perkinsus has been indicated by 18S rRNA sequencing to be rela ted to dinoflagellates, and the opportunity was taken to examine the ultras tructure of the flagellar apparatus of Parvilucifera in detail. Parvilucife ra and its allies, known as perkinsids, share features with both dinoflagel lates and apicomplexans. They do not fit readily into any of these groups b ut appear to form a missing link between them. They are described as a taxo n on level with the other alvelolate phyla, as Perkinsozoa phylum nov. Infection studies showed that Parvilucifera infectans infects several other dinoflagellates, notably Alexandrium spp. which are responsible for PSP (p aralytic shellfish poisoning). A discussion of the ecological role, in term s of biocontrol of harmful algal blooms, is included.