Desmidium quadratum Nordstedt var. quadratum

Araújo, Camila Barbosa de, Bicudo, Carlos Eduardo de Mattos, Takiyama, Luís Roberto & Melo, Sérgio de, 2020, Pseudofilamentous desmids (Zygnematophyceae) from an Amazonian floodplain lake (Macapá, AP, Brazil), Iheringia, Série Botânica (e 2020010) 75, pp. 1-14 : 6

Desmidium quadratum Nordstedt var. quadratum Acta Universitatis lundensis 9: 49, pl. 1, fig. 24. 1873.

( Figs. 11 A-B)

Cell were slightly wider than long, 15-16 × 19-21 μm, 11-14 μm broad at the apex and 18-19 μm broad at the isthmus. Semicells pyramidal-truncated; straight apical margins; lateral margins convergent, undulated, and slightly concave at the subapical region; rounded basal angles; shallow median constriction; open and linear median sinus; hyaline to light brown cell wall; axial chloroplast.

Material examined: BRAZIL, AMAPÁ, Macapá, Curralinho Lake , 14.I.2008, C.B. Araújo (SP469223), 15.IV.2008, C.B. Araújo (SP469226) .

Comments: according to Bicudo & Samanez (2016), presence of D. quadratum var. quadratum Nordstedt in Brazil is somewhat questionable, mainly due to the existence of morphological “major” and “minor” expressions. Furthermore, according to Oliveira (2011), several taxonomic identifications of specimens of this species in the literature are not consistent, since they may have included descriptions and illustrations that do not exactly match those of typical D. quadratum specimens.

Distribution in Brazil: Amazonas ( Souza 2008, Souza & Melo 2010); Bahia ( Oliveira 2011); Goiás ( Dias & Sophia 1994); Pará ( Grönblad 1945, Scott et al. 1965, Förster 1969); Mato Grosso ( De-Lamonica-Freire 1992); Rio de Janeiro ( Sophia 1987, 1999); São Paulo (Borge 1918, Bicudo 1969, Bicudo & Samanez 1984, 2016).

Figures

Figs. 3-15. Pseudofilamentous desmids of Curralinho Lake, Macapá, Amapá, Brazil. 3 A-C. Bambusina borreri. A, B. detailed cells; C. detailed pseudofilament; 4. B. borreri var. brasiliensis; 5 A-B. B. borreri var. majus, detailed cells and pseudofilaments; 6. Desmidium baileyi var. baileyi f. bailey; 7 A-B. D. elegans. A. detailed pseudofilament, B. detailed cell; 8 A-B. D. graciliceps var. graciliceps. A. frontal view of the pseudofilament, B. slight modification of the pseudofilament frontal view; 9. D. graciliceps var. groenbladii; 10 A-C. D. longatum. A. pseudofilament frontal view, B. formation of the elongate conjugation tube, C. zygospore; 11 A-B. D. quadratum var. quadratum. A. detailed pseudofilament, B. detailed cells; 12. D. quadratum var. constrictum; 13 A-B. Groenbladia neglecta var. neglecta. A. detailed pseudofilament, B. detailed cells; 14 A-B. G. neglecta var. elongata. A. detailed pseudofilament, B. detailed cells; 15. Haplozyga armata var. armata. Scale bars = 10 µm.