Parvilucifera infectans norén 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, was found to contain round bodies previously interpreted as the result of sexual reproduction. After two weeks of darkness in the refrigerator, all Dinophysis had died, however, and round bodies were present. These proved to be 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 phagocytic protist. Perkinsus has been indicated by 18S rRNA sequencing to be related to dinoflagellates, and the opportunity was taken to examine the ultrastructure of the flagellar apparatus of Parvilucifera in detail. Parvilucifera and its allies, known as perkinsids, share features with both dinoflagellates and apicomplexans. They do not fit readily into any of these groups but appear to form a missing link between them. They are described as a taxon 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 (paralytic shellfish poisoning). A discussion of the ecological role, in terms of biocontrol of harmful algal blooms, is included.