of the month
didymocarpum * is a rare, poorly known
desmid. In the Netherlands it was reported for the first time in summer
2002. Sampled from a small, shallow, mesotrophic dune pool, in the
first instance only vegetative cells were encountered. Originally,
those cells — on account of their minute median constriction and the
presence of asteroid chloroplasts — were labeled Actinotaenium
diplosporum var. americanum forma minus. However,
on the basis of the characteristically shaped twin zygospores that
were encountered later in the season it was concluded that the algal
material in question fully agreed with Actinotaenium didymocarpum as described from Lapland **.
* Penium didymocarpum Lundell 1871, on the basis of its cell
wall structure was transferred to the genus Actinotaenium by
Coesel & Delfos (1986).
Possibly, A. diplosporum var. americanum forma minus is identic to A. didymocarpum. Further taxonomic investigations
P. & A. Delfos, 1986. New and interesting cases of conjugating desmids
from Lapland. — Nordic Journal of Botany 6: 363-371.