Desmidium quadratum Nordstedt var. constrictum Nordstedt

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 : 6-7

Desmidium quadratum Nordstedt var. constrictum Nordstedt , Kongliga Svenska Vetensk Akademiens Handlingar 22(8): 25. 1888.

( Fig. 12 )

Cell were about as broad as they were long, 35 × 36 μm, 22 μm broad at the apex and 32 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 to slightly deep median constriction; open median sinus; hyaline to light brown cell wall; axial chloroplast.

Material examined: BRAZIL, AMAPÁ, Macapá, Curralinho Lake , 13.V.2008, C.B. Araújo (SP469227) .

Comments: this variety differs from the typically observed characteristics for the species. It presented larger cells with narrower apices and a shallow to slightly deep constriction in the mid region, which results in a constricted appearance of the pseudofilament. Förster (1964) proposed D. quadratum var. constrictum Förster as a new variety, referring to it as D. quadratum f. “maior” Grönblad, based on Grönblad’s (1945) material. These authors divided some specimens of D. quadratum into larger and smaller forms. However, Croasdale et al. (1983) used the name Desmidium quadratum var. constrictum Nordstedt proposed by Nordstedt (1888) and should be considered legitimate because it refers to Wolle’s (1884: pl. 49, fig. 5). The new variety proposed by Förster (1964) based on Brazilian material must be rejected, and its occurrence only reported in Goiás state, Brazil.

Distribution in Brazil: Goiás (Förster 1964).

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.