Nitella townsendii Casanova, 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

Nitella townsendii Casanova , sp. nov.

Type: Northern Territory: Parkin Rd, Livingston , 6 May 2010, P.Dostine 49DW73-4 (holo: DNA!) .

Monoecious. Plants up to 8 cm high, with mucus; apparently rhizomatous ( Fig. 15 a ). Axes 400 µm wide; internodes 10–20 mm long, often longer than the sterile branchlets. Fertile branchlets 6–8 in a whorl ( Fig. 15 e ); 2×furcate; primary segments to 1.5–4 mm long; secondary segments 4–7, some without gametangia up to 3 mm long; some much shorter (0.8 mm) and with gametangia; 2–4 tertiary segments 0.6–1 mm long. Sterile branchlets 6 in a whorl ( Fig. 15 d ); unevenly 2 or 3×furcate; primary segments up to 15 mm long; secondary segments 5–7, up to 6 mm long; tertiary segments 6–8, up to 8 mm long. Fertile and sterile dactyls similar, bicellulate; 0.5–0.8 μm long, tapering to a long, conical, acute end-cell ( Fig. 15 c, g ). Heads not formed; fertile branchlets somewhat contracted; mucus abundant around the gametangia ( Fig. 15 e ). Gametangia conjoined at the fertile branchlet nodes, but antheridia appear to dehisce before oogonia mature ( Fig. 15 b ). Oosporangia single or geminate ( Fig. 15 b, g ), up to 350 µm long; coronula up to 15 µm high, upper cells longer ( Fig. 15 f ). Oospores dark brown, 190–230 µm long × 180–190 µm wide with 7 or 8 striae ( Fig. 15 h ) with robust, figured, porate flanges ~5 μm high; ornamentation of ropy, sinuous vermiculae and verrucae ( Fig. 15 j ). End-cell impressions quite small ( Fig. 15 i ). Antheridia up to 150 µm in diameter ( Fig. 15 i ). Chromosome numbers not known.

Taxonomic notes

The oospores and other morphological characters of this species are most similar to Nitella vermiculata J.Groves from Madagascar; however, the diameter of the vermiculate elements on the oospore wall of N. vermiculata are much narrower, and N. townsendii has a more ropy and perforate flange.

Recognition

Nitella townsendii is monoecious and has bicellulate dactyls and viscous mucus around the gametangia. The dactyls are somewhat in-curved at their tips, and the branchlets have more than five segments at each furcation. The oospores are especially distinctive.

Distribution

Rivers and streams around Darwin.

Etymology

Named for Simon Townsend, who has collected charophytes in the Northern Territory.

Specimens examined

NORTHERN TERRITORY: Billabong next to the Darwin River 4 May 2011, J. Schult t841 ( MEL) .

Figures

Fig. 15. Nitella townsendii (a, b) from specimen J.Schult t841 (MEL), (c–i) from holotype specimen P.Dostine 49DW73-4 (DNA). (a) Habit of whole shoot, scale: 5 mm. (b) Fertile branchlet with central antheridia and lateral oogonia, scale: 1 mm. (c) Sterile dactyls, scale: 0.5 mm. (d) Sterile whorl, scale: 1 mm. (e) Fertile whorl, scale: 1 mm. (f) Oogonium, scale: 100 µm. (g) Branchlet tip with only oogonia and dactyls, scale: 100 µm. (h) Scanning electron microscope (SEM) image of oospore, scale: 100 µm. (i) SEM image of base of oospore, scale: 50 µm. (j) SEM image of detail of oospore wall, scale: 20 µm.