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.

Annulus: A hyaline ring of slightly thickened silicon on a valve surface.

Areolae: A regularly repeated perforation through the cell wall.

Auxospore: A special cell that restores cell size; normally a result of sexual reproduction.

Auxospore Envelope: A hyaline envelope that surrounds the auxospore cell.

Auxosporulation: The process of auxospore formation.

Capitate: Head-shaped.

Fascia: A plain, unthickened transverse strip.

Foramina: Opening on one side of a complex areola.

Homothallic: Possessing both male and female capability in a single morphologically and physiologically identical cell.

Hyaline Line: An unperforated siliceous strip between two striae.

Interstriae: An unperforated siliceous strip between two striae.

Morphogenesis: A developmental sequence that causes an organism to develop its shape.

Mucilage: Glycoproteins and/or exopolysaccharides excreted by some diatoms.

Ocellus: A group of small pores surrounded by a thickened hyaline rim and raised from the surface of the valve.

Oogamous: Sexual reproduction in which the sperm is small and motile, and the egg is larger and nonmotile.

Oogonia: Female gametangia.

Otaria: Membranous costae that occur opposite each other on a valve, especially the genus Rhizosolenia.

Pili: Long siliceous hairs on a diatom valve.

Poroid: Simple unchambered hole through a diatom valve.

Pseudoseptum: A siliceous projection to the cell interior at the edge of the valve.

Rimoportula: A tubelike opening through the cell wall with an internal flattened tube or lip-like slit; also called labiate process.

Rimoportula Tube: The external portion of a rimoportula.

Rostrate: The blunt tapered end of a valve, shaped like a beak.

Spermatogonangia: In sexual reproduction, the cell that produces sperm cells.

Spinules: Little spines.

Uniseriate: Arranged in a single series of cells.

Vegetative Cells: Cells that are a result of asexual division.