Pleurotaenium subcoronulatum (W.B.Turner)

Levanets, Anatoliy & Vuuren, Sanet Janse Van, 2024, New insights into the morphology, taxonomy and geographical distribution of Pleurotaenium subcoronulatum (Zygnematophyceae, Desmidiales), Phytotaxa 655 (2), pp. 144-158 : 149-150

1. Pleurotaenium subcoronulatum (W.B.Turner) West & G.S. West 1895: 44, pl. 5: fig. 33

Basionym: Docidium subcoronulatum W.B. Turner 1893: 29 , pl. III [3]: fig. 1

Synonym: “ Pleurotaenium subcoronulatum var. spinulosum ” Opute, 2000, nom. inval.

Type locality: India, Bengal.

Description: Cells are medium sized, and often attached to each other to form chains ( Fig. 4A ). The semicells are regular in diameter, with a slightly undulated margin. More pronounced undulations occur near the basal swelling, while fainter undulations are present towards the apex ( Fig. 2E ). A prominent basal inflation is present near the isthmus (arrow, Fig. 2E ). The apex is truncated and decorated with 20–26 tubercles. The cell wall may be smooth or finely punctated. Cells are 340–400 μm long, and the width at the basal inflation and apex is 28–32 μm and 24–28 μm, respectively. A short furrow is visible at the base of each tubercle on the apex ( Figs 2F , 4A ). Longer cells were found by several authors in various parts of the world ( Table 1 ). Conjugating, but morphological dissimilar cells, were observed from India resulting in the formation of a broadly oval zygospores, 50–70 µm in diameter ( Ramanathan 1963).

Distribution:

North America: Canada ( Prescott et al. 1975; Poulin et al. 1995), USA ( Smith 1924; Brown 1930; Prescott et al. 1975; Ngo et al. 1987; Dillard 1990; Rosen et al. 2019; Fairbanks 2020).

Central America: Cuba ( Comas 2009).

South America: Brazil ( Thomasson 1977; Melo & Souza 2009; Freitas & Loverde-Oliveira 2013; Costa et al. 2014), French Guiana ( Bourrelly & Couté 1982; Thérézien 1985; Hoff et al. 1995), Paraguay ( Lemmermann 1910), Venezuela ( Sanchez 1992).

Africa: Burkina Faso ( Zongo & Zongo 2016), Côte d’Ivoire ( Lozo et al. 2019), Democratic Republic of the Congo ( Van Oye 1953; Golama Swana Kaketa 1996; Etat des lieux de la biodiversitédans la RD Congo 2014), Madagascar ( West & West 1895), Mozambique ( Rino 1971), Niger ( Tahirou 2013), Nigeria ( Opute 2000; Kadiri 2002; Ekhator et al. 2013, 2014; Ekhator & Alika 2016), Sierra Leone ( Grönblad et al. 1968), South Africa ( Fritsch & Rich 1924; Williamson 1994), Tanzania ( Van Meel 1954), Zimbabwe ( Rich 1935). Lakes on borders of African countries: Lake Moëro [Lake Mweru] ( Van Meel 1954), Lake Victoria ( Cocquyt et al. 1993).

Asia: Bangladesh ( Ahmed et al. 2008; Bhuiyan et al. 2019), India ( Turner 1893; Ramanathan 1963; Tessy & Sreekumar 2011; Gupta 2012; Gupta & Das 2019; Verma et al. 2021), Indonesia ( Krieger 1932; Scott & Prescott 1961; Sulawesty & Lukman 2019; Abudi et al. 2021), Japan ( Okada 1936; Hirano 1956; Kanetsuna 1967; Hirose et al. 1977; Ohtani 1996), Korea South (National species list of Korea 2019), Myanmar ( Burma) ( Skuja 1949), Nepal ( Bando et al. 1989), Singapore ( Pham et al. 2011), Thailand ( Hirano 1992).

Australia and New Zealand: Australia ( Ling & Tyler 1986, 2000; Day et al. 1995; Dingley 2001).

Note: Pleurotaenium subcoronulatum var. spinulosum Opute (2000: 141 , fig. 5.11) was described from Warri/ Forcados Estuaries in Nigeria based on its unique cell wall morphology. Cells are approximately ten times longer than broad, arranged single or in short chains of 2–4 cells. Semicells are with a distinct basal inflation, but with no further undulations ( Fig. 4H ). The apex is slightly expanded and crowned with 12–14 characteristic conical tubercles. The prominent tubercles and the filamentous habit are comparable with the type, but the cell wall differs from any other reported form as it is covered with a tuft of fine hairs or spines over the entire surface ( Fig. 4H ). Cells are 480–512 μm long, and 47–52 μm wide (52–56 μm including the spines).

Unfortunately, Opute’s name is nomenclaturally invalid as the type was not indicated in accordance with Art. 40.1 of ICN ( Turland et al. 2018). Numerous attempts to find Opute’s type material were unsuccessful (none has been found at University of Benin website, and Index Herbariorum does not list any holdings in other herbaria). Due to the poor quality of Opute’s illustration, we decided not to use Art. 40.5 ( Turland et al. 2018) to typify this taxon. In this case, we place this name in synonymy as an invalid name.

Figures

FIGURE 2. Scanning electron micrographs of Pleurotaenium subcoronulatum f. majus Rich (A–D) and P. subcoronulatum (E–F). A) Entire cell of P. subcoronulatum f. majus with two unequal semicells, B) Central part of the cell illustrating the isthmal ring (arrow), C) Apical end of upper semicell with apical tubercles and bordered pits (arrow), and D) Apical end of lower semicell illustrating tubercles with fluted cell wall, E) Small semicell of P. subcoronulatum with inflated basal area (arrow), and F) higher magnificaton of apical end with teeth-like tubercles. Scale bars: 50 µm (A–E) and 25 µm (F).

FIGURE 4. Comparison of the morphology of P. subcoronulatum with closely related infraspecific taxa. A) P. subcoronulatum (from Turner 1893), B) P. subcoronulatum (from West & West 1895, C) P. subcoronulatum f. elongatum (from Prescott et al. 1975), D) P. subcoronulatum var. africanum (from Krieger 1937), E) P. subcoronulatum var. detum (from West & West 1896), F) P. subcoronulatum var. maximum (from Van Oye 1953), G) P. subcoronulatum var. rectum (from Borge 1903) and H) P. subcoronulatum var. spinulosum (from Opute 2000). No scale bars; dimensions indicated in descriptions.