Domoic acid

Domoic acid, which causes amnesic shellfish poisoning (ASP), is an amino acid phycotoxin (algal toxin) found associated with certain algal blooms.

Occurrence
In 1958, domoic acid was originally isolated from the red alga called "doumoi" or "hanayanagi" (Chondria armata )in Japan. "Doumoi" is used as an anthelmintic in Tokunoshima, Kagoshima. Domoic acid is also produced by diatoms of the genus Pseudo-nitzschia. Domoic acid is commercially available.

Toxicology
The chemical can bioaccumulate in marine organisms that feed on the phytoplankton, such as shellfish, anchovies, and sardines. The toxin does not bioaccumulate in the classic sense because it is quickly excreted by fish and shellfish that ingest it. It only accumulates in high numbers in these plankton feeders when the diatom itself is high in number in the surrounding waters. Bioaccumulation or biomagnification typically occurs in lipid-rich tissues, which accumulate toxins over time. In classic bioaccumulation, the older and larger an organism is, the longer it has to accumulate the toxins in its fats, and therefore, the higher the concentration of toxin. In mammals, including humans, domoic acid acts as a neurotoxin, causing short-term memory loss, brain damage, and death in severe cases in Atlantic Canada. Algal bloom are associated with the phenomenon of ASP. Considerable recent research has been carried out by the Marine Mammal Center and other scientific centers on the association of red tides to domoic acid and to resulting neurological damage in marine mammals of the Pacific Ocean. In marine mammals, domoic acid typically causes seizures and tremors.

In the brain, domoic acid especially damages the hippocampus and amygdaloid nucleus. It damages the neurons by activating AMPA and kainate receptors, causing an influx of calcium. Although calcium flowing into cells is a normal event, the uncontrolled increase of calcium causes the cell to degenerate. Because the hippocampus may be severely damaged, long-term memory loss occurs.