Includes abbreviations used on this site.

Apical axis The long axis of a diatom
Arcuate Curved like a bow, arc-shaped, bent along the apical axis
Attenuated Made thin or slender in girth or transverse thickness; tapered off (see Stauroneis anceps)
Biarcuate Curved on both ends
Capitate Having a distinct head; knob-like or swollen at the end
Cingulum A transverse groove that encircles the cell, made up of the girdle bands of a diatom
Cosmopolitan Widely diffused over the globe, found in many locations
Distal raphe end The external terminus of the raphe at the poles or ends of valves
Eccentric Having an axis or point of support that is not centrally placed
Endemic Native or limited to a certain area
Fascia An unornamented area across the middle portion of a valve in pennate diatoms, generally rectangular and band-shaped
Fibulae Internal struts that provide structural support to the raised keel that contains the raphe; extend transapically from the valve face to the valve mantle (Nitschia) or under the raphe in the central reigon (Denticula)
Frustule The siliceous covering of a diatom cell, consisting of two valves, an epivalve (top) and hypovalve (bottom) and their associated cingulum elements
Gibbous Convex, rounded, protuberant; exceeding a semi-circle but less than a circle
Girdle bands The connecting structure between the mantles of the valves in a frustule
Keel A raised or elevated ridge that contains the raphe, formed from a folding of the valve wall
Lanceolate A shape that is wider in the center than at the ends. (see L. muticopsis f. reducta)
LM -Light microscopy Using a microscope in which a beam of light passes through optical lenses to view an image of the specimen.
Pennate diatom A bilaterally symmetric diatom that produces amoeboid gametes
Proximal raphe end The internal terminus of the raphe near the center of valves
Pseudoraphe A false raphe; an unornamented region in the axial area on the hypovalve of monoraphid pennate diatoms
Puncta Pore or perforation through the valve, an areolae is a puncta bounded by an internal or external sieve membrane
Raphe A slit through the valve face of monoraphid and diraphid diatoms, usually situated along the apical axis. This is the structure which enables a diatom cell to move over substrates
Rostrate Terminating in a rostrum, which is a blunt tapered end to the valve resembling a beak
SEM - Scanning Electron Microscopy Using a microscope in which a finely focused beam of electrons is scanned across a specimen, and the electron intensity variations are used to construct an image of the specimen. This type of microscope is ideal for magnifications from 200 to 35,000.
Stauros Where the central nodule (more heavily silicified) is expanded to the valve mantle to form a crosslike structure
Stigma Each of the respiratory openings or breathing-pores; a spiracle
Striae Linear rows of puncta/areolae, usually oriented along transapical axis
Transapical axis The axis perpendicular to the apical axis
Undulate Furnished with wave-like markings
Valve Siliceous part of the frustule containing most of the morphological features used to describe diatoms (taxonmically, morphologically, etc.). Each valve has two surfaces, the face and the mantle








Resources used to help construct this glossary:

  • California Academy of Sciences (CAS) Diatom Collection Glossary
  • Freshwater Algae of North America, Ecology and Classification. Edited by John D. Wehr and Robert G. Sheath. Academic Press of Elsevier Science, San Diego, CA, 2003.