Nitella nitida 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 : 343

Nitella nitida Casanova & Karol , sp. nov.

Type: Manton Dam Recreation Area , 0.45 m depth, 5 Sep. 2010, M. T. Casanova & B. M . Atkinson r754 (holo: DNA!; iso: MEL!, NY!) .

Dioecious. Plants with uneven spreading branchlet whorls; up to 15 cm high; with reproductive structures on shorter whorls ( Fig. 12 a, d ). Axes up to 350 µm wide; internodes up to 30 mm long, approximately as long as the branchlet whorls except in the fertile parts. Fertile branchlets 7 or 8 in a whorl, the male whorls more contracted and shorter than the sterile whorls ( Fig. 12 b ); females similar to the sterile whorls ( Fig. 12 f ). Primary segments on male branchlets up to 10 mm long, longer on female branchlets; secondary segments 3–6, some of them dactyls, 0.1–0.3 mm long; the shorter ones divided into up to 6 tertiary segments, up to 0.3 mm long; sterile branchlets 7 or 8 in a whorl, up to 20 mm long, with long primary segments and often more furcate than fertile branchlets; primary segments up to 13 mm long, unevenly furcate into 3–7 secondary segments which are 4–8 mm long; some again divided into 3–8 tertiary segments, up to 5 mm long ( Fig. 12 g ). Fertile dactyls 3–7; bicellulate, the end-cell shortly conical and acute, confluent with the end of the penultimate cell ( Fig. 12 c ). Sterile dactyls similar to fertile but often longer. Heads not formed, however the fertile whorls are often well separated along the upper axes. Gametangia on separate plants; antheridia single and central at the final 1 or 2 furcations ( Fig. 12 g ); oosporangia single, lateral to the final 1 or 2 fertile branchlet nodes. Oosporangia up to 500 µm long, 300 µm wide with 7 helical stripes ( Fig. 12 e ); coronula up to 30 µm high, the upper cells shorter than the lower cells. Oospores 230–250 µm long × 200–210 µm wide with 5 or 6 flanges; the flanges mostly free of ornamentation, 10–20 µm high ( Fig. 12 h ); ornamentation verrucate-papillate ( Fig. 12 i ), that is small papillae arising from the verrucae, nippled ( Fig. 12 j ). Antheridia up to 100 µm in diameter ( Fig. 12 c ). Chromosome numbers not known.

Taxonomic notes

The oospores of this new species are very similar to those of a specimen collected in 1887 ( W. A.Persieh 48, BM!) and labelled Nitella polyglochin A.Braun ex Nordst. , which was Braun’s collective name for some species related to N. furcata (Roxb. ex Bruzelius) C.Agardh. However , N. polyglochin is described as monoecious, and N. nitida is clearly dioecious (Specimen r754 is male, Specimen r753 is female).

Recognition

This species has interrupted fertile whorls, with very long primary branchlet segments; in some cases, the distal segments appear like little brushes at the tips of the branchlets. This feature is similar to Nitella oollooensis , but in that species the branchlet tips are more uneven and there is a central percurrent branchlet segment. The two can also be distinguished on the basis of oospore ornamentation. Other species of Nitella can be distinguished on the dactyl structure, oospore ornamentation, the presence of abundant mucus or the overall appearance of the branchlet whorls.

Distribution

Nitella nitida was found in shallow water, in the vicinity of Darwin, but quite likely occurs across the wetter parts of the Northern Territory and possibly Queensland.

Etymology

This species is named for Melbourne performer Nitida Atkinson , who was named after Eucalyptus nitida Hook. f. from the Latin nitidus (shining), a suitable name for these taxa and the woman.

Specimens examined

NORTHERN TERRITORY: Manton Dam Recreation Area , 5 Sep. 2010, M. T. Casanova & B. M . Atkinson r753 ( MEL, NY), r744 ( MEL, NY), r757 ( MEL, NY), r762 ( MEL, NY); Fogg Dam, 20 Apr. 1960, R.D. Wood , N. Eddy & A . Wilson 61-4-20-4 ( NY) .

Figures

Fig. 12. Nitella nitida (a–c) from isotype specimen M.T.Casanova & B.M.Atkinson r754 (MEL) and (d–j) from M.T.Casanova & B.M.Atkinson r753 (MEL). (a) Habit of whole male plant, scale: 10 mm. (b) Fertile male branchlet whorl, scale: 5 mm. (c) Male fertile final furcations, scale: 500 µm. (d) Habit of whole female plant, scale: 10 mm, (e) Oogonium, scale: 0.1 mm, (f) Fertile female branchlet, scale: 1 mm, (g) Fertile female branchlet whorl, scale: 5 mm, (h) Scanning electron microscope (SEM) image of oospore, scale: 50 µm. (i) SEM image of detail of oospore wall, scale: 10 µm, (j) SEM image of side view of oospore ornamentation, scale: 10 µm.