Smithsonian Marine Station at Fort Pierce

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Glossary of Terms

The following is a list of commonly used terms in diatom texts, and are included in the species narratives on this site. For terms not defined here, consult one or more of the following texts: Round et al. (1990); Hasle & Syvertsen (1997).

Terms indicated with an asterisk (*) are defined and/or illustrated in the General Morphology of a Diatom Cell portion on this site.

Annulus

a hyaline ring of slightly thickened silicon on a valve surface

Apical Axis *

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

Bilabiate Slit

in the genus Ditylum, a form of rimoportula that has two slits on opposite sides

Capitate

head-shaped

Cingulum *

Claspers

in the genus Rhizosolenia, small strucures clasping the adjacent valve of linked cells

Copula / Intercalary Bands / Pleurae *

Costate Ocellus

in the genus Cerataulus, a thickened hyaline or poroid siliceous area often slightly raised above the valve surface

Epivalve *

Fascia

a plain, unthickened transverse strip

Foramina

opening on one side of a complex areola

Frustule *

Girdle Bands *

Girdle View *

Homothallic

possessing both male and female capability in a single morphologically and physiologically identical cell

Hyaline Line / Interstriae

an unperforated siliceous strip between two striae

Hypovalve *

Macrolabiate

in the genus Coscinodiscus, the larger of two types of rimoportulae

Mantle *

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 hyalne 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

Pervalvar Axis *

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

Transapical Axis *

Uniseriate

arranged in a single series of cells

Valve *

Valve Face *

Valve View *

Valvocopula *

Vegetative Cells

cells that are a result of asexual division


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