Cosmarium trinodulum var. pilgeri Schmidle (1901:49)

Ramos, Geraldo José Peixoto, Santos, Maria Aparecida Dos & Moura, Carlos Wallace Do Nascimento, 2021, Taxonomic notes on some Cosmarium species (Desmidiaceae, Zygnematophyceae) from Brazil, Phytotaxa 483 (3), pp. 291-299 : 297-298

Cosmarium trinodulum var. pilgeri Schmidle (1901:49) ( Figs 8 , 55–59 )

Cell dimensions: 33–37 μm long, 30–35.5 μm wide, isthmus 10–13 μm wide.

Material examined:— BRAZIL. Pantanal dos Marimbus, Andaraí, Bahia State. Sample: HUEFS 241798 .

Habitat: —This variety was found associated with periphyton of Utricularia foliosa . EC 0.12 mS cm-1, DO 7.5 mg L- 1, pH 5.9, TDS 0.05, T 27.6 ºC.

Note:— This variety was described by Schmidle (1901) based on a sample gathered in a brook in the headwaters of the Xingu River, Brazilian Central-West. Over 100 years later, this rare variety, only known till now from its type locality, is being reported again to Brazilian territory, but now to Northeastern Region. It is interesting to note that both samples (from Mato Grosso and Bahia) were collected from similar latitude strips (about 10– 13º south of the Equator) .

The var. pilgeri differs from the nominate variety in having relatively shorter and wider cells, and 3–6 granules around a central granule with a circular pattern. This ornamentation pattern resembles the famous Belgian monument “Atomium”.

Overall, the three Brazilian taxa of Cosmarium trinodulum (var. trinodulum, var. brasiliense , var. pilgeri ) found in the Marimbus are remarkable for polymorphism. However, they have some consistent morphological features, mainly in the granules number and arrangement, which contribute to keep yet them as distinct taxonomic entities: (1) nominate variety generally has more than 13 interconnected granules per semicell, spatially arranged over most part of the semicell; (2) var. brasiliense generally has from 5 up to 13 granules arranged in 1–3 arched series per semicell; (3) var. pilgeri has 3 up to 7 interconnected granules per semicell, arranged in the median or subapical region.

Lastly, the diversity of granulated specimens of Cosmarium from Marimbus is interesting. There are some other similar and non-yet identified taxa in the analyzed samples, which they need further studies to verify whether they are morphological variations of some known species or if they are new to science.

Figures

FIGURES 1–8. Line drawings. 1. Cosmarium boeckii var.areolatum 2. C. clepsydra var. incrassatum 3. C. heptangulare 4. C. kanetsunae 5. C. pygmaeum 6. C. trinodulum 7. C. trinodulum var. brasiliense 8. C. trinodulum var. pilgeri.

FIGURES 33–59. LM and SEM. 33–38. Cosmarium pygmaeum: LM (33–37), SEM (38), frontal view (33–35), lateral view (36), apical view (37), 39–45. C. trinodulum: LM (39–44), SEM (45): frontal view (39–42, 45), lateral view (43), apical view (44), 46–54. C. trinodulum var. brasiliense: LM (46–53), SEM (54), frontal view (46–50, 54), lateral view (51), apical view (52, 53), 55–59. C. trinodulum var. pilgeri: frontal view (55–57, 57—Cell division), lateral view (58), apical view (59). Scale bar: 10 μm, except Fig. 38 (2 μm).