Cosmarium boeckii var. areolatum G.J.P.Ramos & C.W.N.Moura, 2021

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 : 292

Cosmarium boeckii var. areolatum G.J.P.Ramos & C.W.N.Moura , var. nov ( Figs 1 , 9–12 )

Diagnosis:—It differs from the nominate variety in having 7–8 sub-apical granules that are arranged in an ellipsoidal configuration. Cell dimensions: length 19–20 μm, breadth 17–18 μm, breadth of isthmus 5,5–6 μm.

Holotype:— Material numbered ( HUEFS 241798 !) [pro parte] deposited at Herbarium of State University of Feira de Santana, Brazil. Population partially illustrated here in LM ( Figs 1–6 ) and SEM ( Fig. 7 ).

Paratype:—Material numbered ( HUEFS 242434 ) [pro parte] deposited at Herbarium of State University of Feira de Santana, Brazil .

Type locality:— BRAZIL. Pantanal dos Marimbus, Andaraí, Bahia State, Lat. 12° 45’ 53.4” S, Long. 41° 18’ 36.1” W. Sample ( HUEFS 241798 ) collected by G. J. P.Ramos, F. M.Costa & C. W. N.Moura s/n on 23 May 2017 .

Habitat:—The new variety was found on Utricularia foliosa (periphytic habitat). EC 0.06 (± 0.01 mS cm-1), DO 7.1 (± 0.5 mg L- 1), pH 6.8 (± 0.3), TDS 0.02, T 27.3 (± 0.6 ºC), WT 0.6 m.

Note:— Cosmarium boeckii was described by Wille (1880:28) based on material collected in Norway. Despite being a common species, mainly in Europe and North America, in Brazil it is known only in the Central-West Region ( Prescott 1957). There are some infraspecific taxa of this species, differing from the nominate variety generally by cell size and granular arrangement. The main morphological feature of var. areolatum is the presence of granules forming an arrangement like an ellipsoidal halo, and its cell outline, which is irregularly crenate (dentate).

The var. areolatum was rarely found at the study area, occurring only in two samples. The presence of granules forming an arrangement like an ellipsoidal halo is notable in LM as well as SEM observations. It is morphologically similar to Cosmarium anisochondrum Nordstedt (1878: 12) but this species differs by having concentric granules in the midregion of the semicell, and margins slightly crenate.

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 9–32. LM and SEM. 9–15. Cosmarium boeckii var. areolatum: LM (9–12), SEM (15), frontal view (9, 10, 15), lateral view (11, 12), apical view (13, 14), 16–21. C. clepsydra var. incrassatum: frontal view (16–19), lateral view (20), apical view (21), 22–26. C. heptangulare: LM (22–25), SEM (26), frontal view (22–23, 26), lateral view (24), apical view (25), 27–32. C. kanetsunae: frontal view (27–28), lateral view (29, 30), apical view (31, 32). Scale bar: 10 μm, except Fig. 15 (5 μm).