Closterium cynthiaforme Van Westen et Coesel

Van Westen, Marien C. & Coesel, Peter F. M., 2018, Taxonomic notes on desmids from the Netherlands II, with a description of six new species, Phytotaxa 385 (1), pp. 1-12 : 3

Closterium cynthiaforme Van Westen et Coesel stat. et nom. nov. ( Figs 2 , 9–11)

Synonym: Closterium archerianum var. pseudocynthia Růžička 1973 .

Closterium archerianum var. pseudocynthia was described by Růžička (1973: 198, pl. 1: 17–18). The arguments to describe this form as a variety of Cl. archerianum Cleve (in Lundell 1871:77, pl. 5:13) are not quite clear. Cells of Cl. archerianum var. archerianum gradually attenuate towards the somewhat obliquely truncate apices, whereas var. pseudocynthia has a more rounded apex. Moreover, cells of var. pseudocynthia are less slender (length to breadth ratio ≤ 10 versus> 10 in var. archerianum ) and stronger curved (> 155 o, versus <155 o in var. archerianum ). As the epithet already expresses, the cells have more in common with Cl. cynthia De Notaris (1867:65, pl. 7:71). But as the latter is a so-called girdle-band Closterium , affinity with that species is unlikely as well. Furthermore, the finds in Drenthe indicate a different ecology: Cl. archerianum var. archerianum is mainly found in artificial, slightly mesotrophic water bodies such as drinking pits for cattle, ponds and pools close to urban areas, whereas Cl. cynthiaforme is found in shallow, oligo-mesotrophic pools in nature restoration areas. Therefore, in our opinion, Closterium archerianum var. pseudocynthia should be removed from Cl. archerianum and raised to species level. As the name of Cl. pseudocynthia already exists for another taxon (Das & Keshri 2016) we propose the name Closterium cynthiaforme .

The dimensions of Closterium cynthiaforme in Drenthe are: length 90–120 μm, breadth 10.5–12.5, L/B ratio 7.7–10, with 8–10 striae in 10μm

Figures

FIGURES 1–8. 1. Closterium joostenii. 2. Closterium cynthiaforme. 3. Staurastrum subcomptum. 4. Staurastrum exlooënse.5. Cosmarium abbreviatiforme. 6. Cosmarium kouwetsii. 7. Zygospore of Cosmarium spierense with adhering gametangial cells. 8. Cosmarium spierense.