Pleurosigma javanicum
Family: Pleurosigmataceae
Pleurosigma javanicum image
Pleurosigma javanicum  

Species Description: Valves are lanceolate and sigmoid with somewhat acute apices (Fig. 1, exterior of entire valve, SEM). The raphe system is median through most of its length, approaching the margin near the apices (Fig. 3, detail of Fig. 1), where the distal raphe ends curve around the ends of the valve. Several isolated areolae are present at the extreme tip of the valve. The central area is rather small, and the raphe ends overlap and curve sharply away from each other on the valve exterior (Fig. 2, detail of Fig. 1). The external foramina of the areolae are slit-like. The apical axis (length) is 107-136µm and the transapical axis (width) is 25-28µm. The transverse striae are 24-25 in 10µm and the oblique striae are 20-21 in 10 µm, crossing at an angle of 64 degrees.

A brief description was presented initially in Cleve & Grunow (1880), later expanded by Cleve (1894). The IRL material corresponds to the original type material from Java, in Cleve & Möller Type Slide 145 (Sterrenburg, personal communication, 18 November 2013). That suggests a tropical preference for this species. Although quite rare in the IRL, it was found in the Banana River and south to the Jupiter Inlet at various times of the year, and may have been misidentified as P. rigidum or as P. angulatum. Both of these have been previously described from the IRL.

Cleve PT. 1894. Synopsis of the naviculoid diatoms. Kongl Svenska VetenskAkad Handl 26: 1-194.

Cleve PT, Grunow A. 1880. Beiträge zur Kentniss der arctischen Diatomeen. Kongl Svenska VetenskAkad Handl 17: 1-121.

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.

Pleurosigma javanicum image
Pleurosigma javanicum  
Pleurosigma javanicum image
Pleurosigma javanicum  
Pleurosigma javanicum image
Pleurosigma javanicum