A single-celled microscopic algae which has a predator/prey relationship with fish in its ecosystem. During a large portion of its life cycle, Pfiesteria piscicida exists in a nontoxic cyst form at the bottom of a river. When those (cysts) detect certain substances (e.g., excreta) emitted by live fish, the Pfiesteria piscicida transform into an amoeboid or dinoflagellate form, which secretes a water-soluble neurotoxin into the water (which incapacitates nearby fish). The Pfiesteria piscicida next attach themselves to those fish, excrete a lipid-soluble toxin which destroys the epidermal layer of the fish’s skin, allowing the Pfiesteria piscicida to begin “eating” the fish’s tissue. Human exposure to the neurotoxin apparently causes short-term memory loss.
A unicellular marine organism, which may or may not produce a toxin, depending on environmental conditions. When toxic, it has been implicated in the death of millions of fish in the estuaries of North Carolina, Delaware, and Maryland. The toxin can become aerosolized, and if humans are exposed to it, severe neurological, mental, and physical illness may occur. Specific therapy to combat the toxin is not available, but concomitant infections can be treated with tetracyclines.