Haslea gretharum
Family: Naviculaceae
Haslea gretharum image
Haslea gretharum  

Species Description: This is another member of the group formerly included in the section Fusiformes of the genus Navicula (Hustedt 1931-66) and transferred to Haslea by Simonsen (1974). The original description for this species is: “Valves lanceolate with acute to somewhat rounded ends, 150-200µm long, 19.5-22µm wide”. Raphe straight with extremely approximate central pores. Central and axial areas lacking. Structure very delicate; transapical striae parallel, 18-19 in 10µm; longitudinal striae hardly visible (best in interference contrast), 36-40 in 10µm.” Figure 1 (light micrograph, modified from Simonsen 1974; plate 32, Fig. 1a) represents the holotype.

Many of the species transferred into Haslea (Simonen 1974) have not been examined with electron microscopy. A single valve of a Haslea was observed at Port Canaveral, Banana River that corresponds closely to an unpublished photo of H. gretharum type material from the Indian Ocean (F. Hinz via F. Sterrenburg personal communication, 4 Sept. 2014). This valve, the only one seen, is slightly smaller than Simonsen’s description (Fig. 2, SEM external view; Fig. 3, detail of Fig. 2). It does not show the internal structure, so the identification is tentative. Other identification possibilities include H. clevei (Sterrenburg et al. 2015) and H. frauenfeldii (Grunow) Simonsen; until more material is available, this identification is tentative.

Hustedt F. 1931-1966. Die Kieselalgen Deutschlands, Österreich und der Schweiz. In: Dr. L. Rabenhorst’s Kryptogamen-Flora von Deutschlands, Österreich und der Schweiz 7(1): 1-920, 7(2): 1-845, 7(3): 1-816. J Cramer Verlag, Weinheim.

Simonsen R. 1974. The diatom plankton of the Indian Ocean expedition of R/V “Meteor” 1964-1965. “Meteor”Forschungsrgebnisse, Reihe D 19: 1-66, Pl. 1-41.

Sterrenburg FAS, Tiffany MA, Herwig WE, Hargraves PE. 2015. Seven new species expand the morphological spectrum of Haslea. A comparison with Gyrosigma and Pleurosigma (Bacillariophyta). Phytotaxa 207: 143-162.

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.

Haslea gretharum image
Haslea gretharum  
Haslea gretharum image
Haslea gretharum  
Haslea gretharum image
Haslea gretharum