Cosmarium palatiniforme Van Westen & Coesel, 2021

Van Westen, Marien C. & Coesel, Peter F. M., 2021, Taxonomic notes on desmids from the Netherlands IV, with a description of another five new species, Phytotaxa 522 (3), pp. 240-248 : 246

Cosmarium palatiniforme Van Westen & Coesel spec. nov. ( Figs 2 , 18, 19, 20 , 33 )

Diagnosis: Cells a little longer than broad with a rather deep, linear, almost closed sinus. Semicells in frontal view sub-oblong with convex lateral sides and broadly rounded angles. Semicell margin with some 14 crenations, those on the lateral sides rather deep and emarginate, those at the apex most flattened. Semicells in frontal view just above the isthmus with a broad inflation furnished with 6-8 flattened, longitudinal costae, usually indistinctly granulate and paired with a separate granule near the isthmus. Supraisthmial ornamentation separated from radiate series of intramarginal granules by an unsculptured zone. Intramarginal granules joining the marginal crenations arranged in pairs. Outline of semicells in apical view elliptic, the central part inflated. Outline in lateral view ovate. Chloroplast with a single, central pyrenoid.

Dimensions: cell length 32–35 µm, breadth 27–31 µm, L/B = 1.1–1.2, thickness 18–19 µm, isthmus 10–13 µm.

Type:— THE NETHERLANDS. Drenthe: rain puddle on sandy track in estate De Holmers near Elp, 52.911518 ° N, 6.630222° E. Van Westen, 19 Februari 2017 (holotype L! Hugo de Vries Lab 2021.03, preserved as a fixed natural sample and represented by our fig. 2) .

Differentiating diagnosis:—The above-diagnosed taxon very well agrees with C. palatinum Dick as represented in Grönblad (1936, p. 11, pl. 2: 31). However, semicells of C. palatinum as originally diagnosed by Dick (1930, p. 43, pl. 8: 7) are characterized by a supraisthmial inflation furnished with distinctly separated granules arranged in a pattern of 5 by 3 series. Because of the questionable identity of our taxon with Dick’s C. palatinum we prefer to describe it as a separate species. As far as could be traced, no other records of C. palatinum have been published. Presumably, we have to do with a rare species with a predominantly boreal distribution. In the Netherlands it is only known from a few locations.

Figures

FIGURES 1–8. Drawings 1. Cosmarium grantii (from Eexterveld, province of Drenthe, the Netherlands). 2. C. palatiniforme. 3, 4. C. neonotabile (no 4 from Holmers, province of Drenthe, the Netherlands). 5. C. neocrenatum. 6. C. sphagnicola. 7. C. sphagnicoliforme (with zygospore). 8. C. regnesiforme.

FIGURES 18–23. LM photographs. 18–20. Cosmarium palatiniforme (from Holmers). 21–23. C. regnesiforme (21, 23 from Dwingelderveld, province of Drenthe, the Netherlands, 22 from type location). Scale bar = 10 µm

FIGURES 30–38. SEM photographs. 30. Cosmarium grantii (from Eexterveld). 31. C. neocrenatum (from Iceland). 32. C. neonotabile (from Holmers). 33. C. palatiniforme (from type location). 34. C. sphagnicola (from Eexterveld). 35. C. sphagnicoliforme (from type location). 36, 37. C. regnesiforme (from type location). 38. C. regnesi (Zeijen, province of Drenthe, the Netherlands). Figures 30–33: Scale bar = 10 µm, Figures 34–38: Scale bar = 5 µm