Causative Organism: Pseudo-nitzschia spp.(1)

Approximate Size of Pseudo-nitzschia spp: The apical axis of cells is 38–50 μm long and the transapical axis is 2.5– 4.0 μm long (4)

Approximate Size of Nitzschia sp: 45–55 μm long and 9-11 μm wide (5)

Mode of Activity: Domoic acid binds to the synaptic receptors of the kainic acid receptor. This allows sodium ions to enter the post- synaptic membrane, inducing an increase in the permeability of cacium ions that leads to cell dysfunction or death (6)

Toxicity: LD50 of 2.4 mg domoic acid/kg of body weight in mice (12*)

Geographic range: 55o N - 55o S (12, 13*)

Species:

P. australis (4*), P. delicatissima, P. fraudulenta (6), P. multiseries (1), P. multistriata (4), P. pseudodelicatissima (1), P. pungens, P. seriata, P. turgidula (6), and N. navis-varingica (5)

Impacts of Toxin

Marine Food Web:

Toxin is bio-magnified and/or bio-transformed up the food web. (1, 7, 10)
Mortality in free-ranging brown pelicans and Brandt's cormorants in Santa Cruz during a Pseudonitzschia australis bloom.  Domoic acid was found in high concentrations in anchovies, the primary food source of the affected birds (7).  Sea lion deaths have also been attributed to ASP (9, 10).

Behavioral: Sea lions subjected to domoic acid displayed persistent seizures with obtundation, limbic system seizure injury, and degeneration within the neuropil of the hippocampus, amygdala, pyriform lobe, and other limbic structures (10)

Economic:

Closure of a variety of shellfish beds from harvesting when 20 mg domoic acid per gram shellfish tissue is identified in organisms in the United States, European Union, New Zealand and Australia (13*

Human Health

Name of Malody: amnesic shellfish poisoning (ASP) (1)

Symptoms: headache, seizures, hemiparesis, ophthalmoplegia, and abnormalities of arousal ranging from agitation to coma. Long term symptoms include severe anterograde-memory deficits, with relative preservation of other cognitive functions (11).

Incidents: (12*, 13*)

 *and references cited therein. 

References

1.  Amzil, Z. et al., 2001. Domoic acid accumulation in French shellfish in relation to toxic species of Pseudo-nitzschia multiseries and P. pseudodelicatissima. Toxicon, 39(8), 1245-1251. 
2. Bird, C.J. & Wright, J.L.C., 1989. The shellfish toxin domoic acid. World Aquacult, 20, 40–41. 
3. James, K.J. et al., 2005. Amnesic shellfish poisoning toxins in bivalve molluscs in Ireland. Toxicon, 46(8), 852-858.
4. Orsini, L. et al., 2002. Toxic Pseudo-nitzschia multistriata (Bacillariophyceae) from the Gulf of Naples: morphology, toxin analysis and phylogenetic relationships with other Pseudo-nitzschia species. European Journal of Phycology, 37(2), 247 - 257.
5. Lundholm, N. & Jvind Moestrup, Ø., 2000. Morphology of the marine diatom Nitzschia navis-varingica, sp.nov (bacillariophyceae), another producer of the neurotoxin domoic acid. Journal of Phycology, 36(6), 1162-1174.
6. Bates, S.S., 2000. Domoic-acid-producing diatoms: another genus added! Journal of Phycology, 36(6), 978-983.
7. Work, T.M. et al., 1993. Domoic acid intoxication of brown pelicans and cormorants in Santa Cruz, California. ELSEVIER, AMSTERDAM(NETHERLANDS). 1993.
8. Davidovich, N.A. & Bates, S.S., 1998. Sexual reproduction in the pennate diatoms Pseudo-nitzschia multiseries and P. pseudodelicatissima (bacillariophyceae). Journal of Phycology, 34(1), 126-137.
9. Gulland, E.M.D. et al., 2002. Domoic acid toxicity in Californian sea lions (Zalophus californianus): clinical signs, treatment and survival. Veterinary Record, 150(15), 475-480.
10. Silvagni, P.A. et al., 2005. Pathology of Domoic Acid Toxicity in California Sea Lions (Zalophus californianus). Veterinary Pathology Online, 42(2), 184-191.
11. Teitelbaum, J.S. et al., 1990. Neurologic Sequelae of Domoic Acid Intoxication Due to the Ingestion of Contaminated Mussels. New England Journal of Medicine, 322(25), 1781-1787.
12. Jeffery, B. et al., 2004. Amnesic shellfish poison. Food and Chemical Toxicology, 42(4), 545-557.
13. Lefebvre, K.A. & Robertson, A., 2010. Domoic acid and human exposure risks: A review. Toxicon, 56(2), 218-230.