Cosmarium margigranulatum, Costa & Ramos & Moura, 2023

Costa, Fabiana De Matos, Ramos, Geraldo José Peixoto & Moura, Carlos Wallace Do Nascimento, 2023, New taxa of Cosmarium and Euastrum (Zygnematophyceae) from the North Coast of Bahia, Brazil, Phytotaxa 632 (2), pp. 193-200 : 197

Cosmarium margigranulatum F.M. Costa & C.W.N.Moura sp. nov. ( Figs. 3 , 15–18 )

Diagnosis: —Cells as long as broad, median constriction deep, sinus closed, linear; semicells reniform, smooth median face, angles rounded covered by granules, apex slightly projected with three protrusions; cell oblong in apical view. Cell dimensions: length 36.8–41.3 μm, breadth 41.6–44.6 μm, breadth of isthmus 12.7–16.2 μm.

Holotype:— Material numbered ( HUEFS 263036 !) [pro parte], deposited at the Herbarium of the State University of Feira de Santana, population partially illustrated here ( Figs. 3 , 15–18 ).

Paratypes:— Material numbered ( HUEFS 263040) [pro parte], deposited at the Herbarium of State University of Feira de Santana.

Type locality:— BRAZIL. Bahia: Camaçari, Camaçari-Mirim River, Lat. 12°42’23.1’’ S, Long. 38°15’27.2’’ W, 29 November 2019, F. M. Costa & J. T.X. Neto s/n ( HUEFS 263036).

Habitat:— Periphytic on Eleocharis acutangula ; water conductivity 0.04 mS. cm-1 (± 0.01); dissolved oxygen 7.6 mg.L- 1 (± 0.1); pH 7.3 (± 0.9); total dissolved solids 0.02 ppt (± 0.01); water temperature 28.3 ºC (± 1.3).

Etymology:— The specific epithet refers to the ornamentation composed of various granules located at the margins of semicells.

Differential diagnosis:— Cosmarium margigranulatum differs from the other species of Cosmarium by having a very distinct ornamentation: concentrated granules along the margins of the semicells, but lacking in the central region.

Morphologically, the newly described species resembles Cosmarium ornatum var. pseudolagoense Förster (1964: 399) . However, this latter variety differs by having a concentric ring of granules on the face of the semicells and short spines at the angles of the semicells.

Figures

FIGURES 2–5. Line drawings. 2. Cosmarium lineatum sp. nov. 3. C. margigranulatum sp. nov. 4. C. panamense var. therezienii var. nov. 5. Euastrum evolutum var. truncatum var. nov. Scale Bar: 10 μm.

FIGURES 6–18. Cosmarium lineatum sp. nov. (6–14): frontal view (6–12), details of the thick layer of mucilage (6), lateral view (13), apical view (14). C. margigranulatum sp. nov. (15–18): frontal view (15–16), lateral view (17), apical view (18). Scale Bar: 10 μm.