Cosmarium tetragonum

Cosmarium tetragonum is a species of green algae in the family Desmidiaceae. It is a freshwater species with a worldwide distribution.

Cosmarium tetragonum
Scientific classification Edit this classification
(unranked): Viridiplantae
(unranked): Charophyta
Class: Zygnematophyceae
Order: Desmidiales
Family: Desmidiaceae
Genus: Cosmarium
Species:
C. tetragonum
Binomial name
Cosmarium tetragonum
(Nägeli) W.Archer in Pritchard 1861[1]
Varieties

Cosmarium tetragonum var. elegans (Roy & Bisset) West & G.S.West 1908[2] (syn. C. elegans)

Synonyms

Euastrum tetragonum Nägeli

Description

The nominate variety (var. tetragonum) is about 35 to 48 µm long, and 20 to 26 µm wide, 14 to 18 µm thick, with an isthmus about 6 to 12 µm long. Semicells are roughly rectangular in outline, with undulate margins; each side has about four bumps and the top side has about two bumps.[3]

Varieties

Cosmarium tetragonum is variable and several varieties have been described. They are:

  • Variety lundelii differs from the nominate variety that the lateral bumps are unequal; the two median bumps are larger.[3]
  • Variety bipapillatum also has two median bumps that are larger, but also has a protuberance right at the base of the semicell, near the isthmus.[3]
  • Variety ornatum has a crease that follows the margin of the cell; the crease may also have projections near the apex of the semicell.[3]
  • Variety intermedium has stout cells that are 1.5 times as long as broad; semicells are more trapezoidal.[3]

References

  1. Pritchard, A. (1861). A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign. Fourth edition enlarged and revised by J. T. Arlidge, M.B., B.A. Lond.; W. Archer, Esq.; J. Ralfs, M.R.C.S.L. ; W. C. Williamson, Esq., F.R.S., and the author. pp. i-xii, 1- 968, 40 pls. London: Whittaker and Co., Ave Maria Lane. (description page 732)
  2. West, W. & West, G.S. (1908). A monograph of the British Desmidiaceae. III. pp. [i]-xv, [1]-274, pl. 65-95. London: The Ray Society. (description page 20)
  3. Prescott, G. W.; Croasdale, H. T.; Vinyard, W. C.; Bicudo, C. E. M. (1981). A Synopsis of North American Desmids. Part II: Desmidiaceae: Placodermae. Section 3. Lincoln: University of Nebraska Press. p. 720. ISBN 9780835737920.
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