Lamprothamnium stipitatum Casanova, Austral.

Casanova, Michelle T. & Karol, Kenneth G., 2023, Charophytes of Australia’s Northern Territory - I. Tribe Chareae, Australian Systematic Botany 36 (1), pp. 38-79 : 45-47

Lamprothamnium stipitatum Casanova, Austral. Syst. Bot. 26: 285 (2013)

Type: Weelarrana Salt Lake , Pilbara region, WA, 6 Jan. 2011, M. T. Casanova r888 (holo: PERTH!; iso: MEL!) .

Dioecious. Plants appearing more like a narrow species of Chara than Lamprothamnium (distinguished by the decumbent stipulodes, narrow axes and spreading bract cells, as well as the saline habitat), calcified. Axes 200–300 μm in diameter, ecorticate; internodes up to 5 cm long, a little shorter than the longest branchlets ( Fig. 4 a ). Stipulodes in a single row, opposite the branchlets ( Fig. 4 d ), up to 6 around, but often absent or reduced, downward-pointing, up to 200 μm long. Branchlets 6 in a whorl, up to 45 mm long, usually ~ 12 mm long, ecorticate, very narrow, up to 100 μm in diameter ( Fig. 4 b, c ), basal branchlet cell up to 2 mm long, branchlet end segments generally 2-celled, the terminal cell much shorter than the others, bract cells verticillate and spreading but usually very short, 100–200 μm long ( Fig. 4 c ). Fertile parts not much contracted, no real distinction between fertile and sterile whorls. Gametangia foliar and internal to the base of the branchlet whorl, sessile and stipitate, solitary and geminate. Oosporangia up to 500 μm long, 300 μm wide, stipitate (stipes up to 2 mm long) and sessile inside the base of the branchlet whorl, sometimes singular, sometimes geminate; on the branchlets, sessile and stipitate ( Fig. 4 d ), sometimes geminate ( Fig. 4 f ). Coronula of triangular cells (star-shaped from above; Fig. 4 e ). Oospores black, 360–375 mm long, 200–210 μm wide, 8 or 9 striae of low, undulating ridges ( Fig. 4 h ), oospore ornamentation granulate ( Fig. 4 i ), end cell impression up to 65 mm at widest diameter ( Fig. 4 j ). Antheridia large, up to 550 mm in diameter, bright orange, sessile and stipitate inside the base of the branchlet whorl, sessile on the lowest two branchlet nodes ( Fig. 4 b ). Vegetative reproduction not known. Chromosomes n = 14 ( Fig. 4 g ).

Distribution

In brackish temporary wetlands in northern inland Australia: the Pilbara region of Western Australia and the Tanami Desert.

Etymology

‘ Stipitatum ’ in Latin means provided with a stipe or a stalk, this species being named for the long-stalked gametangia.

Notes

Lamprothamnium stipitatum is the only dioecious Lamprothamnium known from Northern Territory and has very large antheridia. It can be distinguished from dioecious L. heraldii A.García & Casanova on the basis of its stipitate gametangia and paucity of bract cells and stipulodes. This is just the second specimen seen, but it confirms the validity of the species. Lamprothamnium species frequently have gyrogonites, a character that is missing in ecorticate Chara species.

Specimens examined

NORTHERN TERRITORY: Fiddlers Lake, Tanami Desert , 14 Aug. 2001, P. K.Latz 17982 (DNA) [distinctive, but very poor material, intermixed with filamentous algae] .

Figures

Fig. 4. Lamprothamnium stipitatum from the holoype specimen M.T.Casanova r888 (PERTH). (a) Habit of whole plant, scale bar: 5 cm. (b) Fertile antheridial branchlet whorl, scale bar: 1 cm. (c) Fertile antheridial branchlet whorl with basal antheridia, scale bar: 1 cm. (d) Fertile female branchlet whorl, scale bar: 1 cm. (e) Coronula of triangular cells, scale bar: 100 µm. (f) Pair of oogonia on a branched stipe, scale bar: 100 µm. (g) Light micrograph of antheridal cells in metaphase, chromosomes n = 14, 1000× magnification, image enhanced and chromosomes outlined. (h) Scanning electron micrograph (SEM) of oospore, scale bar: 100 µm. (i) SEM of detail of oospore wall, scale bar: 20 µm. (j) SEM of basal cell impression, scale bar: 50 µm.