Pleurosigma diverse-striatum
Family: Pleurosigmataceae
Pleurosigma diverse-striatum image
Pleurosigma diverse-striatum  

Species Description: Valves only slightly or not sigmoid, broadly lancolate with slightly rostrate apices. The raphe is somewhat sigmoid (Fig. 1, entire valve exterior, SEM) and sharply hooked at the apices (Fig. 3, detail of Fig. 1), with the central raphe endings highly variable, according to Sterrenburg (2001), but seen here somewhat deflected to opposite margins and not overlapping (Fig. 2, detail of Fig. 1). In contrast to most species of Pleurosigma, the external foramina of the areolae are circular rather than slit-like (Fig. 2)

The cells are recorded as 55-90µm long, 1-22µm wide, with 25-27 transverse and 18-22 oblique striae in 10µm, crossing at about 60 degrees. The species is known from the Caribbean Sea, Pacific Ocean, Indonesia, and coast of Kenya (Sterrenburg 2001). It is rare in the IRL system, found only once near the Fort Pierce Inlet (Fig. 1): slightly smaller than elsewhere, measuring 51.5 X 13µm with 25 transverse and 22 oblique striae in 10µm, crossing at about 62 degrees.

Sterrenburg FAS. 2001. Studies on the genera Pleurosigma and Gyrosigma: The types of Shadbolt and related taxa. Proc Acad Nat Sci Philadelphia 151: 121-127.

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 diverse-striatum image
Pleurosigma diverse-striatum  
Pleurosigma diverse-striatum image
Pleurosigma diverse-striatum  
Pleurosigma diverse-striatum image
Pleurosigma diverse-striatum