Lioloma elongatum (Grunow) Hasle 1997
Family: Thalassionemataceae
Lioloma elongatum image
Lioloma elongatum  

Species Description: This genus consists of very elongate and narrow needle-like cells that are differentiated from the closely related Thalassionema by the absence of small spines along the valve margin. The three known species were formerly in the genus Thalassiothrix (Hasle & Syvertsen 1997). In L. elongatum, the two ends of the cell are different. The “head” pole is somewhat club-shaped with a single apical spine (Fig. 1A, modified from Hasle & Syvertsen 1997; and Fig. 2, SEM); the “foot” pole is gradually narrowed, and lacks a spine (Fig. 1B, modified from Hasle & Syvertsen 1997; and Fig. 4, live cell, phase contrast). Rudimentary secondary spines have been reported on the “head” pole (Rivera and Cruces 2007). A wide hyaline area (sternum) extends the length of the valve, and a row of complex areolae extends along each valve margin (Fig. 3, SEM), becoming reduced near the apices. Scattered along the length of the cell are many small chloroplasts (Fig. 4, valve view of foot pole, live cell, phase contrast; Fig. 5, girdle view of head pole, live cell, phase contrast)

The reported size from literature sources is 738-2040µm long, 3-4µm wide, with 8-14 areolae in 10µm. It was found rarely in the IRL, mostly about 1200µm long, and 3.6-3.8µm wide, with 10-11 areolae in 10µm (Fig. 3). It has a wide tropical distribution, mostly reported from the Pacific Ocean, but has probably been overlooked or misidentified in some areas, since it resembles the more common L. pacificum that is also occasionally present in the IRL. Further details of the morphology and distribution are found in Hasle (2001). It was found only near the Fort Pierce Inlet in summer of 2008 and 2013, and is probably adventitious.

Hasle GR, Syvertsen EE. 1997. Marine Diatoms. pp. 5-385. In: Tomas C (Ed.), Identifying Marine Diatoms and Dinoflagellates. Academic Press (NY).

Hasle GR. 2001. The marine, planktonic diatom family Thalassionemataceae: morphology, taxonomy and distribution. Diat Res 16: 1-82.

Rivera P, Cruces FR. 2007. On the diatom Lioloma elongatum (Grunow) Hasle (Thalassionemataceae) off the Chilean coast. Diat Res 22: 491-493.

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.

Lioloma elongatum image
Lioloma elongatum  
Lioloma elongatum image
Lioloma elongatum  
Lioloma elongatum image
Lioloma elongatum  
Lioloma elongatum image
Lioloma elongatum  
Lioloma elongatum image
Lioloma elongatum