A new type of seafood toxicity, called amnesic shellfish poisoning, was described from 107 human cases after individuals consumed mussels containing domoic acid harvested from Prince Edward Island, Canada, in 1987. Most of these cases experienced gastroenteritis, and many older persons or others with underlying chronic illnesses developed neurologic symptoms including memory loss. Standard treatment procedures for the neurologic condition were not effective and three patients died. Domoic acid is a known neurototoxin, and it is believed that in these cases enough toxin was absorbed through the gastrointestinal system to cause lesions in the central nervous system. The most severely affected cases still have significant memory loss 5 years after the incident. The source of the domoic acid was identified as the pennate diatom, Nitzschia pungens f. multiseries, which was ingested by the mussels during normal filter feeding. A possible biosynthetic pathway for the toxin has recently been determined. Certain m...