Species Description: In a recent publication, definition of the genus Haslea was expanded significantly (Sterrenburg et al. 2015). Haslea species are characterized by a sandwich-structured valve consisting of an internal grate-like basal layer and an external tegumental layer perforated by continuous longitudinal fissures. These two layers are shored by longitudinal “bulkheads” (saepes) that are perforated so that they form fence-like rows of columns. The valve contour of many of the 30+ species is fusiform or lanceolate. In Sterrenburg et al. (2015) H. amicorum is defined in part as: valve rather broadly lanceolate, 32−39µm long, 7.5–8.5µm wide. Striae are transverse radiate, circa 11 in 10µm; longitudinal striae strongly curved, circa 22 in 10µm; expanded central areas visible in SEM, and central raphe endings straight. The holotype and isotype of H. amicorum are presented here as Figs. 1 & 2. In Fig. 1 (adapted from holotype, light microscope by Herwig in Sterrenburg et al. 2015, figure 65) the basal layer is clearly defined. The isotype (Fig. 2, SEM of exterior, modified from Sterrenburg et al. 2015, figure 67) shows the slightly expanded central area, the interrupted proximal longitudinal fissures, and the straight raphe endings

The IRL has at least two Haslea species that are very similar to H. amicorum but differ in ways whose taxonomic significance is uncertain. The first species was found in the Mosquito Lagoon and differs from H. amicorum in that: it lacks an expanded central area, the longitudinal striae are not interrupted (Fig. 3, valve exterior SEM), the central raphe fissures are slightly deflected to the same side (Fig 4, detail of Fig. 3, central raphe fissures deflected to the same side [arrows], sample ML104), and the size (14.7 X 2.9µm) is too small for H. amicorum. The second species was found in the northern IRL, is similar in size and apical raphe endings to H. amicorum, but differs in the same ways as the Mosquito Lagoon example (Fig. 5, external (lower) and internal (upper) views of valves of the same cell, SEM; Fig. 6, detail of median external valve from Fig. 5, with central raphe fissures deflected to the same side [arrows], sample B12S15). Because the range of morphological variability within the recently described H. amicorum is unknown, these variants are included as belonging to that taxon with the caution that they may eventually be described as novel species.

The species is known only from Birdrock, LaJolla, CA, and possibly the IRL.

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.