Nitella boreali-australis 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 : 329-331

Nitella boreali-australis Casanova & Karol , sp. nov.

Type: Mitchell Creek , Northern Territory, 24 May 2010, P.Dostine 12DW23-2 (holo: MEL! [spirit]) .

Nitella pseudoflabellata f. bancroftii R.D. Wood, Nova Hedwigia 22: 69 (1971) , nom. inval., nom. prov.

[ Nitella mucosa auct. non. (Nordst.) J.Groves: J.Groves in J.Groves & G. O.Allen, Proc. Roy. Soc Queensland 46: 44 (1935)].

Monoecious. Plants fine and flexible, mucus-covered,> 10 cm high. Axes up to 500 µm wide; internodes up to 10 mm long, shorter than the branchlet whorls ( Fig. 4 a ). Fertile branchlets 7 or 8 in a whorl, smaller and less furcate than the sterile whorls; primary segments up to 5 mm long, secondary segments 5 or 6, 0.5–1.5 mm long, divided into 4–6 tertiary segments of which one can be a dactyl, up to 0.5 mm long, further divided into 4 or 5 dactyls ( Fig. 4 c ); sterile branchlets 7 or 8 in a whorl, 10–20 mm long with longer segments than fertile branchlets; primary segments up to 10 mm long, secondary segments 4–7, 3–4 mm long, divided into 3–6 tertiary segments (=dactyls), up to 2 mm long, sometimes 1 or 2 again divided into 3–5 dactyls ( Fig. 4 b ). Fertile dactyls 3–5, up to 1 mm long, but usually 0.5–0.7 mm long, bicellulate; the end-cell conical and acute, confluent with the end of the penultimate cell ( Fig. 4 d ). Where a dactyl is formed at the second furcation, the dactyls can appear 3 cells long (i.e. a suppressed furcation). Sterile dactyls are similar to fertile dactyls but up to 2 mm long. Mucus-covered heads present, really consisting of sequentially smaller whorls distally. Male and female gametangia on the same plant; antheridia single and central in the lowest 2 furcations ( Fig. 4 c ); oosporangia single, lateral at all but the lowest furcation ( Fig. 4 c ). Oosporangia up to 400 µm long, 300 µm wide with 8 or 9 helical stripes, coronula up to 30 µm high, the upper cells slightly longer than the lower cells. Oospores 210–230 µm long, 190–210 µm wide with 8 or 9 flanged striae ~7 µm high ( Fig. 4 e ); the ornamentation fibrous-papillate and porate; the wall appears to be constructed of flocculate fibres, built into papillae occasionally, with rimmed pores (variolae) also occasional ( Fig. 4 f ). Antheridia up to 200 µm in diameter. Chromosome numbers not known.

Taxonomic notes

Three specimens of Nitella were collected by T. L. Bancroft in Queensland, two growing at ‘Stannary Hills’ in 1909 (possibly at the same locality, but the collection details are not specific) and one in Murphy’s Creek in 1910. James Groves (in Groves 1935) identified the two specimens from Stannary Hills as Nitella mucosa (Nordst.) J.Groves and N. orientalis T.F.Allen , and the specimen from Murphy’s Creek as N. phauloteles J.Groves. Wood and Imahori (1965) referred only to the specimen from Murphy’s Creek and provided an illustration ( Wood and Imahori 1964, icon 275). Wood (1971) listed a specimen ‘Stannary Hills: Bancroft in 1909’ under N. pseudoflabellata var. imperialis T.F.Allen , allocating it the provisional designation of ‘form…(8) bancroftii’, but did not distinguish between the two Bancroft specimens collected in this locality. Wood (1971) also amalgamated N. pseudoflabellata with N. mucosa , and N. orientalis with N. phauloteles (all of which are separate species). Although the epithet bancroftii was provisionally attached to one of these specimens, neither is used here as type material, and owing to the potential for confusion, the name ‘ bancroftii’ is not adopted for the taxon at species rank.

Recognition

A very soft, flabellate and mucus-covered monoecious species, distinguished from Nitella limosa Casanova & Karol by the two-celled dactyls. On the basis of oospore similarity, N. boreali-australis is probably closely related to N. imperialis (T.F.Allen) Sakayama from Japan, but that species has less porate oospores, gametangia missing from the first and last furcations, longer internodes and shorter branchlets.

Distribution

On the basis of the localities in Queensland and the Northern Territory, it is assumed that this species will be found across the wet tropics in northern Australia.

Etymology

The name boreali-australis literally means ‘northernsouthern’, but the intent is to refer to northern Australia.

Specimens examined

NORTHERN TERRITORY: Groote Eylandt, 18 May 1948, R. L. Specht A28 ( BM, NY); Groote Eylandt , 18 May 1948, R. L. Specht A29 a ( NY); Port Darwin , 4 Apr. 1896, T. B. Blow A103 ( BM) . QUEENSLAND: Stannary Hills, 1909, T. L. Bancroft ( BM); Lake Eacham , 11 Sep. 1993, T. J. Entwisle 2310 ( MEL); Mareeba , 28 Apr. 1962, H. S. McKee 9373 ( NY) .

Figures

Fig. 4. Nitella boreali-australis from specimen P.Dostine 12DW23-2 (DNA). (a) Habit of whole plant, scale: 10 mm. (b) Sterile whorl, scale: 5 mm. (c) Fertile branchlet, scale: 1 mm. (d) Dactyls, scale: 100 µm. (e) Scanning electron microscope (SEM) image of oospore, scale: 100 µm. (f) SEM image of detail of oospore wall, scale: 20 µm.