Species Description: This species somewhat resembles Nitzschia ventricosa, but is much larger and has different ultrastructure. As in N. ventricosa, the valves are lanceolate with very long slender rostrate apices that may be unequal in length (Fig. 1, entire valve, SEM). The raphe is excentric; the striae are transverse. The fibulae subtending the raphe vary somewhat in size and density, and a larger central space is present (Fig. 2, detail of Fig. 1). The prominent irregularly spaced ribs seen in N. ventricosa are lacking in N. longissima. The few cells seen in the IRL were 310-330µm long and 7µm wide, with 40-42 striae in 10µm. The fibulae number 6-7 in 10µm. These measurements are consistent with the dimensions given in various literature sources. The species is widely distributed; it was rare in the IRL system, as was also observed by Navarro (1982).

Navarro JN. 1982. Marine diatoms associated with mangrove prop roots in the Indian River, Florida, U.S.A.  Biblio Phycol 61: 1-151.

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.