A new species of parasite, Parvilucifera sinerae sp. nov., isolated from a bloom of the toxic
dinoflagellate Alexandrium minutum in the harbor of Arenys de Mar (Mediterranean Sea, Spain), is
described. This species is morphologically, behaviourally, and genetically (18S rDNA sequence)
different from Parvilucifera infectans, until now the only species of the genus Parvilucifera to be
genetically analyzed. Sequence analysis of the 18S ribosomal DNA supported P. sinerae as a new
species placed within the Perkinsozoa and close to P. infectans. Data on the seasonal occurrence of
P. sinerae, its infective rates in natural and laboratory cultures, and intra-species strain-specific
resistance are presented. Life-cycle studies in field samples showed that the dinoflagellate resting
zygote (resting cyst) was resistant to infection, but the mobile zygote (planozygote) or pellicle stage
(temporary cyst) became infected. The effects of light and salinity levels on the growth of P. sinerae
were examined, and the results showed that low salinity levels promote both sporangial germination
and higher rates of infection. Our findings on this newly described parasite point to a complex
host—parasite interaction and provide valuable information that leads to a reconsideration of the
biological strategy to control dinoflagellate blooms by means of intentional parasitic infections.
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