Pfiesteria piscicida

Pfiesteria piscicida
Scientific classification
Domain:	Eukaryota
(unranked):	Sar
(unranked):	Alveolata
Phylum:	Dinoflagellata
Class:	Dinophyceae
Order:	Phytodiniales
Family:	Pfiesteriaceae
Genus:	Pfiesteria
Species:	P. piscicida
Binomial name
Pfiesteria piscicida Steidinger & Burkholder

Pfiesteria piscicida is a dinoflagellate species of the genus Pfiesteria that some researchers claim is responsible for many harmful algal blooms in the 1980s and 1990s on the coast of North Carolina and Maryland. Piscicida means "fish-killer".

Early research suggested a very complex life cycle of Pfiesteria piscicida with up to 24 different stages, spanning from cyst to several amoeboid forms with toxic zoospores. Transformations from one stage to another depend on environmental conditions such as the availability of food. However these results have become controversial as additional research has found only a simple haplontic life cycle with no toxic amoeboid stages and amoeba present on attacked fish may represent an unrelated species of protist.

Pfiesteria presumably kills fish via releasing a toxin into the water to paralyze its prey. This hypothesis has been questioned as no toxin could be isolated and no toxicity was observed in some experiments. However, toxicity appears to depend on the strains and assays used.Polymerase chain reaction-analyses suggested that the organism lacks the DNA for polyketide synthesis, the type of toxins associated with most toxic dinoflagellates. Researchers from the NOAA National Centers for Coastal Ocean Science, the National Institute of Standards and Technology, the Medical University of South Carolina, and the College of Charleston (S.C.) have formally isolated and characterized the toxin in the estuarine dinoflagellete Pfiesteria piscicida as a metal complex and free radical toxin and also have identified how the organism transforms from a non-toxic to toxic state.

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