Wood, Casanova & Karol, 2023

Casanova, Michelle T. & Karol, Kenneth G., 2023, Charophytes of Australia’s Northern Territory - II. Tribe Nitelleae, Australian Systematic Botany 36 (4), pp. 322-353 : 348-350

Nitella tumulosa Zaneveld , Blumea 4: 86 (1940)

Nitella mucronata f. tumulosa (Zaneveld) R.D. Wood , Taxon 11: 18 (1962); Nitella furcata f. tumulosa (Zaneveld) R.D. Wood , Revis. Charac. 1: 526 (1965).

Type: Java,?Korthals (lecto: L n.v. [specimen in a small packet adjacent to the ‘TYPE’ label], fide R.D. Wood in R.D. Wood and K.Imahori, Revis. Charac. 1: 527 (1965)).

Monoecious. Plants up to 25 cm high; tangled and spreading ( Fig. 16 a ). Axes 750–1000 µm wide; internodes up to 33 mm long, as long as the sterile branchlets. Fertile branchlets 6 in a whorl; 2 or 3×furcate ( Fig. 16 d ); primary segments up to 5 mm long; secondary segments 1–4, up to 4 mm long; 2–4 tertiary segments up to 4 mm long; 2–3 quarternary segments, very short, up to 200 μm long (=dactyls); sterile branchlets 6 in a whorl; 2× furcate ( Fig. 16 b ); primary segments 15–20 mm long; secondary segments 1–3, up to 18 mm long; tertiary segments 2 or 3, up to 1 mm long. Fertile and sterile dactyls similar; bicellulate, 50–200 μm long, tapering to a conical, acute end-cell ( Fig. 16 e ). Heads not formed; fertile branchlets somewhat contracted, no mucus present. Gametangia conjoined at the fertile branchlet nodes ( Fig. 16 f ). Oosporangia single or geminate; coronula up to 15 µm high, upper cells longer ( Fig. 16 c ). Oospores golden brown ( Fig. 16 g, h ); up to 240 µm long × 225 µm wide with 7 prominent ridges ( Fig. 16 i ), ornamentation a beaded incomplete reticulum ( Fig. 16 h, j ). Antheridia up to 300 µm in diameter ( Fig. 16 f ). Chromosome numbers not known.

Taxonomic notes

This determination is based on the illustration and description of the lectotype provided in Wood and Imahori (1964, icon 267) and on Sakayama et al. (2005) who illustrated a similar oospore under the name Nitella tumulosa . The specimens from the Northern Territory largely agree with the description of N. tumulosa var. typica (nom. inval.) by Zaneveld (1940), except for having smaller oospores and usually fewer segments at each furcation. However, Zaneveld’s illustration of the oospore (and perhaps the species name) was based on a second specimen (which he designated var. pumila , meaning ‘dwarfed’) ( Zaneveld 1940; Wood and Imahori 1964, icon 268). The illustration shows small mounds or ‘tumuli’ on the oospore wall, rather than the ‘papillate or beaded imperfect reticulum’ described by Sakayama et al. (2005) or the papillate appearance illustrated by Imahori (in Wood and Imahori 1964, icon 267). On the weight of evidence, without having viewed the type material, but in agreement with the description of the oospore illustrated by Sakayama et al. (2005) the name N. tumulosa is applied here.

Recognition

The short, usually paired dactyls on uneven branchlets, monoecy and clustered gametangia are diagnostic for this species.

Distribution

Thailand, Malaysia, Indonesia and the Northern Territory, in shallow, shaded, slow-flowing or still water.

Etymology

Named for the appearance of the oospore wall, interpreted by Zaneveld (1940) to have tumuli, or low mound-like structures. It seems that this description refers to the oospore of Nitella tumulosa var. pumila rather than to that of the type variety.

Specimens examined

NORTHERN TERRITORY: Koolendong Range, perennial creek, 13 Mar. 1989, C. R.Dunlop 8290 & G. J.Leach (DNA); Billabong next to the Darwin River, 4 May 2011, J.Schult t840 ( MEL); 7 km E of Boggy Hole , James Range , 8 June 2003, P. K.Latz 18905 (DNA) .

Figures

Fig. 16. Nitella tumulosa from specimen J.Schult t840 (MEL). (a) Habit of whole plant, scale: 5 mm. (b) Apical whorls, scale: 1 mm. (c) Oogonium, scale: 100 µm. (d) Fertile whorl, scale: 1 mm. (e) Dactyls, scale: 0.2 mm. (f) Placement of gametangia, scale: 1 mm. (g) Light micrograph (LM) of oospore, scale: 100 µm. (h) LM of detail of oospore wall, scale: 20 µm. (i) Scanning electron microscope (SEM) image of oospore, scale: 100 µm. (j) SEM image of detail of oospore wall, scale: 20 µm.