Chara aridicola Casanova & Karol, 2023

Casanova, Michelle T. & Karol, Kenneth G., 2023, Charophytes of Australia’s Northern Territory - I. Tribe Chareae, Australian Systematic Botany 36 (1), pp. 38-79 : 47-49

Chara aridicola Casanova & Karol , nom. nov., stat. nov.

Chara contraria var. australis A.Braun, Linnaea 25: 708 (1853). Type: in Nova Hollandiae interiore prope Cudnaka, Oct. 1851, F. v. Mueller 5 (holo: MEL!) .

[ Chara vulgaris var. vulgaris auct. non L.: R.D.Wood, Nova Hedwigia 22: 14–16 (1971)]

Monoecious. Plants up to ~ 100 mm high, heavily calcified. Axes 500–1400 µm in diameter ( Fig. 5 a ); 2× corticated, aulacanthous (i.e. spine cells appear to be in furrows because the primary cortical cells are smaller), 18–24 cells around ( Fig. 5 d ). Spine cells globose or conspicuous, 60–200 μm long, 50–70 μm in diameter. Stipulodes inconspicuous, in 2 rows, twice the number in each row as the number of branchlets in the adjacent whorl, uppers 100–300 μm long, lowers 50–150 μm long, downward pointing or globose. Branchlets partly and often incompletely corticated (on the lowest 1–3 branchlet internodes), 8–10 in a whorl, up to 17 mm long, segments 6 or 7, terminated by a single cell ( Fig. 5 b ). Bract cells innermost up to 1.5 mm long, ~2 of them, outer up to 250 μm long, bracteoles 2, shorter than innermost bract cells but longer than the immature oosporangia. Gametangia conjoined singly at the lowest 3 corticated branchlet nodes. Very rarely there are 2 oosporangia above a single antheridium. Oosporangia 1100–1200 μm long, 500–630 μm wide, coronula 150 × 280 μm, somewhat spreading ( Fig. 5 c ). Antheridia up to 500 µm in diameter. Oospores black, 750–820 μm long and 450–500 μm wide with 13–17 ridged striae ( Fig. 5 e ), fossa smooth ( Fig. 5 f ), end-cell impression ~140 μm across ( Fig. 5 g ). Gyrogonites present. Chromosomes n = 28 (specimen Casanova p780).

Distribution

In semi-permanent bores, quarry ponds and springs of the Northern Territory and South Australia; the water chemistry has not been recorded.

Etymology

‘ Aridicola ’, from Latin aridus, dry, and - cola, dwelling, describing the species’ preference (particularly the type material) for arid zones, referring to its occurrence in arid and semi-arid regions of the Northern Territory, Western Australia and South Australia

Notes

Braun (1853) described this species as a variety in 1853 on the basis of material collected by von Mueller, and speculated that the large oospore size (larger than Chara contraria A.Braun ex Kütz. from Europe) was because of nutrient availability ( Nordstedt 1887). Groves in Groves and Allen (1935) recorded one specimen from Queensland and did not refer to material described by Braun (1853). Wood (1962) united all previously recognised varieties and forms of C. contraria with C. vulgaris . This was repeated with reference to Australian material ( Wood 1971). The Australian material is different from the type material of C. contraria in Europe, which is tylacanthous (i.e. with spine cells on the larger cortical cells) with conspicuous stipulodes, and C. vulgaris , which usually has brown oospores, conspicuous stipulodes and is more completely corticated on the branchlets. The oospores of C. aridicola also differ in size and ornamentation from those of C. contraria (<750 μm long, somewhat porate) and C. vulgaris (<750 μm long, papillate to verrucate).

The name given by Braun (1853) was C. contraria var. australis . Since the epithet australis was already occupied by a species in subgenus Charopsis , a new epithet has been given, namely, aridicola .

This species has corticated axes and partly corticated branchlets (the lowest 1–3 branchlet internodes) and gametangia only at the branchlet nodes with cortex adjacent to them, large black oospores with gyrogonites. It is similar to C. behriana (A.Braun) Casanova , which has partial or no cortication on the fertile branchlet nodes. The other corticated species of Chara in the Northern Territory have either three times corticated axes ( C. setosa Klein ex Willd. , C. globularis Thuill. , C. zeylanica Klein. ex Willd. ) or completely naked branchlets and one row of stipulodes.

Specimens examined

NORTHERN TERRITORY: Barkly Tableland, Brunette Downs, Crows Nest Bore , 11 July 2001, J. A. Risler & C. P . Mangion 835 (DNA, NT) .

SOUTH AUSTRALIA: Woakwine Quarry , 1 Nov. 2010, M. T. Casanova r846 ( BM, MEL, NY) .

Figures

Fig. 5. Chara aridicola, (a–d) from M.T.Casanova P780, and (e–g) from the type specimen Mueller 5 (MEL). (a) Habit of upper axis of plant, scale bar: 5 mm. (b) Branchlet whorl, scale bar: 1 mm. (c) Gametangia, with bracteoles and bract cells; scale bar: 100 µm. (d) Transverse section of axis, scale bar: 0.5 mm. (e) Oospore in side view; scale bar: 200 µm. (f) Detail of oospore wall; scale bar: 2 µm. (g) Base of oospore; scale bar: 50 µm.