Species Description: Valves are straight and lanceolate with very long, slender rostrate apices (Fig. 1, entire valve interior, SEM). These apices may be of unequal or equal length (Fig. 3, living cell, phase contrast). The raphe is strongly excentric; the interstriae are transverse, diminishing to single areolae in the rostrate apices (Fig. 2, detail of Fig. 1). Valve length is about 145-160µm and width is 8-10µm. The interstriae number about 34 in 10µm. Fibulae subtending the raphe are 7-10 in 10µm, slightly more numerous in the rostrate apices (Fig. 2). Irregularly spaced ribs traverse the valve interior, averaging about 10 in 10µm.

Witkowski et al. (2000) give a much broader range of metrics for this species, but the IRL examples are similar to those reported from the IRL by Navarro (1982) and from Guam by Lobban et al. (2012). It was rare in the IRL, usually in the southern areas, which is consistent with being described as a “warm water” species.

Lobban CS, Schefter M, Jordan RW, Arai Y, Sasaki A, Theriot EC, Ashworth M, Ruck EC, Pennisi C. 2012. Coral-reef diatoms (Bacillariophyceae) from Guam: new records and preliminary checklist, with emphasis on epiphytic species from farmer-fish territories. Micronesica 43: 237-479.

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

Witkowski A, Lange-Bertalot H, Metzeltin D. 2000. Diatom Flora of Marine Coasts I. Iconographia Diatomologica 7: 1-925.

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.