Home / Diatoms / Pennate / Colonies / Biraphes / Pseudonitzschia
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Name derivation:
Classification:
Pseudo-nitzschia H. Peragallo 1900; 48 of 63 species descriptions are currently recognized taxonomically (Guiry and Guiry 2014). Order Bacillariales; Family Bacillariaceae
Morphology:
Distinguished, in part, from the genus Nitzschia by their ability to form chains (Hasle 1994), with the exception that Pseudonitzschia that can also be present as single cells (Lelong et al. 2012).
Similar genera:
Nitzschia (unicells)
Habitat:
Freshwater and marine.
Toxicity enhanced by exposure to copper (50 μg L^-1):
At least 12 species of Pseudonitzschia are on the IOC-UNESCO 'HABs Taxon list' as producers of domoic acid (DA), a neurotoxin. A non-toxic strain of P. delicatissima suffered an increase in mortality when exposed to 50 µg L-1 copper, while a toxic strain of P. multiseries was insensitive to the same exposure (Lelong at al. 2012).  Apparently DA production is triggered by copper when present at more than trace concentrations (Fuentes and Wikfors 2012). Clam flats are periodically closed to harvesting along the coast of New England whenever blooms of P. spp. are observed as a precaution against the presence of toxic strains even though most species produce little or no DA most of the time increasing the stress level of commercial shellfish growers (Wikfors 2016).
References:
Guiry, M.D. and G.M. Guiry 2014. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 30 May 2014. Hasle, G.R. 1994. Pseudo-nitzschia as a genus distinct from Nitzschia (Bacillariophyceae). Journal of Phycology 30: 1036–1039. Fuentes, S. and G.H. Wikfors 2012. Control of domoic acid toxin expression in Pseudo-nitzschia multiseries by copper and silica: Relevance to mussel aquaculture in New England (USA). Marine environmental research 83:23-28. Lelong, A., H. Hégaret, P. Soudant, and S.S. Bates 2012. Pseudo-nitzschia (Bacillariophyceae) species, domoic acid and amnesic shellfish poisoning: revisiting previous paradigms. Phycologia 51(2):168-216. Lelong, A., D.F. Jolley, P. Soudant and H. Hégart 2012. Impact of copper exposure on Pseudo-nitzschia spp. physiology and domoic acid production. Aquatic Toxicology 118-119:37-47. Wikfors, G.H. 2016. Recent Pseudo-Nitschia/ASP Closures in Southern New England. East Coast Shellfish Growers Association 4:1 and 16.