Demoic acid, a potent neurotoxin, has been isolated from the diatom species Nitzschia pungens (phytoplankton) under certain environmental conditions, particularly silica depletion. When this species is ingested by shellfish, it is concentrated and represents a neurological hazard to any human who consumes them. This phenomenon was brought to the awareness of the public during an episode of poisonings in Prince Edward Island, Canada after eating mussels. This recent linkage of demoic acid with shellfish poisoning ( within the last two years) is of particular concern since the diatom Nitzschia pungens var. multiseries is a ubiquitous species thriving in many of our coastal waters. Dr. Fryxel has succeded in cloning the organism both from the Canadian bloom as well as from Galveston Bay. Because there is virtually nothing known about the regulation of the toxin production in this species especially with regard to life cycle stages, it is critical that the cycles of demoic acid production be worked out.
