Species Description: There are at least six species of Pseudo-nitzschia in the IRL system, whose distribution and identities are only partially known. This species was first described from Brazil samples, but has subsequently been found in tropical coastal waters of the Atlantic and Pacific oceans. It forms stepped colonies of a few to many cells (Fig. 1, a 2-cell colony, LM brightfield), with individual cells overlapping by about 10%. The valves are mostly linear through most of their length, tapering gradually to broadly rounded apices (Fig. 2, entire valve, SEM). The interstriae are transverse to the longitudinal axis and consist of a double row of areolae (Fig. 3, external (lower) and internal (upper) valve apices, SEM) except near the valve apex. The raphe is excentric, subtended by fibulae (Fig. 3). The raphe lacks a central nodule, and lacks a larger interspace between the two central fibulae. Each cell has two chloroplasts (Fig. 1)
The size range in Lundholm et al. (2002) is 12-65µm in the apical axis (length) and 1.8-3.0µm in the transapical axis (width). The fibulae and striae are about equal in number (Figs. 2, 3) at 20-26 in 10µm. Further ultrastructural details are in Lundholm et al. (2002). The species is closely related to P. americana and P. linea, which have not been found in the IRL system (as yet). This species was found near the Fort Pierce and Jupiter Inlets, suggesting that is adventitious.
Lundholm N, Hasle GR, Fryxell GA, Hargraves PE. 2002. Morphology, phylogeny and taxonomy of species within the Pseudo-nitzschia americana complex (Bacillariophyceae) with descriptions of two new species, Pseudo-nitzschia brasiliana and Pseudo-nitzschia linea. Phycologia 41: 480-497.