Desmid of the month
November 2002

Staurastrum chaetoceras

Staurastrum chaetoceras is one of the few desmid species which are encountered more frequently and more abundantly in eutrophic, alkaline waters than in oligotrophic, acideous waters. In a nutrient-rich environment a high cell division rate may be realized, probably the reason why this desmid species can compete with chlorococcalean green algae like Scenedesmus, Pediastrum, Oocystis etc which are also characterized by high reproduction rates (Spijkerman & Coesel 1998).
S. chaetoceras may occur both as a biradiate form (semicells provided with two processes) and a triradiate form (semicells with three processes). In hydrobiological literature, triradiate forms often are labeled wrongly S. paradoxum (see e.g. Nygaard 1945, pl. 4, fig. 57).
Possibly, radiation in S. chaetoceras is affected by season (Reynolds 1940). Also the length of the arm-like processes may vary. In cells originating from deep waters cell processes use to be much longer than in those collected from shallow water bodies often partly filled in by aquatic weeds. Presumably, development of long processes in deep waters is an adaptation to a planktic habitat (increase of cell surface : cell content ratio, by which increase of form resistance, by which lower sinking velocity).

References:

• Spijkerman, E. & P.F.M. Coesel, 1998. Ecophysiological characteristics of two planktonic desmid species originating from trophically different lakes. — Hydrobiologia 369/370: 109-116.
  
  
• Nygaard, G. 1945. Dansk Planteplankton. — Gyldendalske Boghandel, Nordisk Forlag, Copenhagen, 52 pp.
  
  
• Reynolds, N., 1940. Seasonal variations in Staurastrum paradoxum Meyen. — New Phytologist 39: 86-98