Desmid of the month
August 2008

Xanthidium octocorne

In former times this species was accounted the genus Arthrodesmus 1. The genus name Arthrodesmus Ralfs having appeared to be illegitimate 2, nowadays our species under discussion usually is placed in the genus Xanthidium3. As some of the characteristics of that genus (such as an ornamented, median inflation of the semicell body) are wanting, for this and some allied species Compère 4 designated  a separate genus, Octacanthium. In practice, however, that latter genus name is but seldom used.

Xanthidium octocorne, named after its 8-angled cells, hardly can be confused with any other species. In the Netherlands it is rather common in oligo-mesotrophic moorland pools, less common in fen hollows. Zygospores are only incidentally encountered.

References

  1. West, W. & West, G.S., 1912: A Monograph of the British Desmidiaceae. Vol. IV. — Ray Society, London.
  2. Compère, P., 1976: The typification of the genus name Arthrodesmus (Algae-Chlorophyta). — Taxon 25: 359-360.
  3. Coesel, P.F.M. & Meesters, J., 2007: Desmids of the Lowlands. — KNNV Publishing, Zeist.
  4. Compère, P., 1996: Octacanthium (Hansgirg) Compère, a new generic name in the Desmidiaceae. — Nova Hedwigia, Beiheft 112: 501-507.

Image © Marien van Westen

Xanthidium octocorne. Each of the 8 angles is provided with a long spine. Notice also the highly elongate isthmus.

Cell dimensions (L x B, including spines): ca 35 x 30 µm.

 


Image © Marien van Westen

Zygospore of Xanthidium octocorne