A DESMID OF THE GENUS EUASTRUM -
RARE IN BRITAIN 

by Bill Ells, UK

 
 
 
'A Treatise on the British Freshwater Algae' by G.S. West 1904 (revised edition 1927) has a photograph of ‘Plankton from Loch Ruar, Sutherland’ on the frontispiece. Diatoms and several species of the desmid genus Staurastrum can be seen, also the desmid Euastrum verrucosum var. planktonicum W.&.G.S.West 1903. In Fig.1. indicated with an arrow.

A number of the same species, rarely seen in Britain, were found in a freshly gathered sample from Loch Ruar in 1993 (Fig.2). It is still to be found in the same Loch after 90 years.

W.& G.S.West in their Vol.2. of 'The British Desmidiaceae' 1905, give the habitats only in Scotland at Loch Ruar and Nan Cuinne.

I would be interested to know if it has been recorded since from elsewhere in Britain.

Beginners Note. Desmids of the same species which differ from the type first described are divided into varieties or forma. Thus the above species Verrucosum of the genus Euastrum was first described by C.G.Ehrenberg in 1848. There are three varieties listed in 'A Check-list of the Desmids of the British Isles' including planktonicum.

Thanks to Dr. A.Joyce for providing the sample.

Comments by e-mail are welcomed to Comments to the author sent via our contacts page quoting page url plus : ('wells','')">William (Bill) Ells.
 
 

References
'A Check-list of the Desmids of the British Isles' 1991 By A.J. Brook and D.B.Williamson. Freshwater Biological Associaton, Occasional Publication No.28.


 
  
ellseu1a.jpg (17560 bytes)
Figure 1
ellseu2.jpg (10439 bytes)
Figure 2

 
 

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