Pleurotaenium tenuissimum Kurt Förster ex C.B.Araújo & C.E.M.Bicudo, 2023

Araújo, Camila Barbosa de, 2023, Taxonomic and nomenclatural notes on two desmid species from Brazil (Desmidiaceae, Zygnematophyceae), Notulae Algarum 269, pp. 1-4 : 2-4

Pleurotaenium tenuissimum Kurt Förster ex C.B.Araújo & C.E.M.Bicudo , sp. nov.

Replaced designation: “ Pleurotaenium tenuissimum Kurt Förster ”, Algological Studies/Archiv für Hydrobiologie, Supplement Volumes 28: 246, 1981, nom. inval.

Description: Cells longer than wide; semicell cylindrical, apex subquadrangular with 4 more or less conical rounded warts squarely arranged; lateral margins parallel, abruptly attenuated to the apex; median constriction shallow; median sinus poorly developed; no central swelling; cell wall hyaline; chloroplast axial; 4-8 pyrenoids by semicell. Cells 238-255 μm long, 6.5-8 μm wide, 2.5-3 μm wide at apex.

Holotype: Scott & al. (1965: pl. 30: fig. 34, as “ Pleurotaenium tridentulum var. tenuissimum ”; ICN Art. 40.5, Turland & al. 2018), here reproduced as Fig. 4 (fig. 33, left).

Type locality: Arapiuns River, a tributary of the Tapajós River, State of Pará, Brazil.

PhycoBank Registration: 103602

Etymology: From Latin tenuis, - e (adj.), thin, fine, slender (narrow); superlative tenuissimus,- a, - um, (very slender).

Occurrence in Brazil: This species is reported from the Amazon region as Pleurotaenium tridentulum var. tenuissimum Grönblad & Croasdale ”, nom. inval.; Amazonas state ( Scott & al. 1965; Förster 1969, 1974; Uherkovich & Rai 1979, just citation); Pará state ( Scott & al. 1965), as “ Pleurotaenium tenuissimum Kurt Förster ”, nom. inval. ( Förster 1981).

We are grateful to Professor Michael Guiry and several reviewers for their valuable recommendations leading to an improvement of the manuscript.

Araújo, C.B., Furtado, M.F.M., Melo, S., Takiyama, L.R., Cantuária, P.C., Bicudo, C.E.M. (2022). Some interesting desmids (Desmidiaceae, Zygnematophyceae): first records, taxonomic notes, and distribution for the Amazon Brazilian flora. Check List 18 (6): 1337–1346, 13 figs.

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Prescott, G.W., Croasdale, H.T. & Vinyard, W.C. (1975). A synopsis of North American desmids. Part II. Desmidiaceae: Placodermae. Sect. 1. pp. 1-275, 57 pls. Lincoln: University of Nebraska Press.

Scott, A.M., Grönblad, R. & Croasdale, H. (1965). Desmids from the Amazon Basin, Brasil. Acta Botanica Fennica 69: 3–93.

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Turland, N.J., Wiersema, J.H., Barrie, F.R., Greuter, W., Hawksworth, D.L., Herendeen, P.S., Knapp, S., Kusber, W.-H., Li, D.-Z., Marhold, K., May, T.W., McNeill, J., Monro, A.M., Prado, J., Price, M.J. & Smith, G.F., editors (2018). International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) adopted by the Nineteenth International Botanical Congress Shenzhen, China, July 2017. Regnum Vegetabile, Vol. 159. pp. [i]- xxxviii, 1–253. Glashütten:

Uherkovich, G. & Rai, H. (1979) Algen aus den Rio Negro und seinen Nebenflüssen. Amazoniana 6 (4): 611–638.

as originally illustrated by Scott & Croasdale (in Scott & al. 1965: p. 32, pl. 4, figs 69-70 as “ Euastrum foersteri ”). Fig. 3 . Euastrum foersteri sp. nov.: as originally illustrated by Förster (1969: 33, pl. 9: figs 22, 23. Scale bar: fig. 22: 30µm; fig. 23: 50 µm, as “ Euastrum foersteri ”). Fig. 4 . Pleurotaenium tenuissimum sp. nov.: holotype (left “33”), the original illustration of “ Pleurotaenium tridentulum var. tenuissimum ” published by Grönblad & Croasdale (in Scott & al. 1965: 30, pl. 2: figs 33, 34). Fig. 5 . Pleurotaenium tenuissimum sp. nov.: holotype originally illustrated by Förster (1969: 28, pl. 6: figs 8-10. Scale bar: figs 8-9: 50 µm; fig. 10: 30 µm) as “ Pleurotaenium tridentulum var. tenuissimum ”. Fig. 6 . Pleurotaenium tenuissimum sp. nov.: material originally illustrated by Förster (1974: 153, pl. 4: figs 8, 9) as “ Pleurotaenium tridentulum var. tenuissimum ”.

Figures

Figs. 1-6. Nomenclatural types of desmid names proposed herein. Fig. 1. Holotype (top two views) of Euastrum foersteri sp. nov.: original illustration of “Euastrum arciferum var. longispinum Kurt Förster & Eckert” (in Förster 1964: p. 349, pl. 6: fig. 5). Fig. 2. Euastrum foersteri sp. nov.: