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Pseudo-nitzschia: Description

The diatom genus responsible for producing domoic acid is named Pseudo-nitzschia. Unlike Alexandrium, Pseudo-nitzschia is often observed in low numbers along the California coast. This diatom can also increase in numbers rapidly, producing blooms of millions of cells per liter and dominating the phytoplankton community for extended periods of time.

Photograph of chains of Pseudo-nitzschia (approximately 100x)

Pseudo-nitzschia is a chain forming pennate diatom. There are many species within the genus Pseudo-nitzschia, and most are difficult to distinguish from one another with routine light microscopy. Some species of this diatom are known to produce domoic acid, while others do not appear to produce this toxin.

 

The individual cells in a chain overlap their neighbor cells at the tip. This overlapping pattern progresses in a "stairstep" fashion.

Photograph of Pseudo-nitzschia chail illustrating overlapping pattern of cells

 

Each cell contains two chloroplasts that appear as heavily pigmented areas separated by a clear spot in the center of the cell, which is actually the nucleus.

Photograph of Pseudo-nitzschia chain illustration location of chloroplasts and nucleus.

 
 
Last modified on: 3/11/2010 9:30 AM