Nitella micklei Casanova

Casanova, Michelle T. & Karol, Kenneth G., 2023, Charophytes of Australia’s Northern Territory - II. Tribe Nitelleae, Australian Systematic Botany 36 (4), pp. 322-353 : 340

Nitella micklei Casanova in M. T.Casanova & J. L.Porter, Muelleria 31: 55 (2013)

Type: WESTERN AUSTRALIA. Mulga Downs Outcamp Claypan , 17 Aug. 2006, M. T. Casanova PBS17 : r114 (holo: MEL!).

Dioecious. Plants sometimes calcified, homeoclemous, up to 90 mm tall, internodes up to 35 mm long ( Fig. 10 a ). Axes stout, up to 650 µm in diameter. Fertile branchlets 5 or 6 in a whorl, up to 2 mm long, 1–22×furcate ( Fig. 10 b, d, e ). Primary segments up to 1.5 mm long, 2 or 3 secondary segments to 1.2 mm long; rarely 2 or 3 tertiary segments up to 0.5 mm long. Sterile branchlets 5 or 6 in a whorl, up to 18 mm in total, 1(–2)×furcate; primary segments up to 6 mm long; 2 or 3 secondary segments, up to 2 mm long; rarely 2 or 3 tertiary segments, up to 2 mm long ( Fig. 10 c ). Dactyl cells swollen or inflated 1–2 mm long, 0.5–1 mm wide, sometimes narrowing distally to be confluent with the mucronate end-cell. End-cell 75 µm long × 30–40 µm wide at the base ( Fig. 10 f ). Fertile dactyls as for sterile; individual segments can be less inflated on male plants. Gametangia on separate plants ( Fig. 10 d, f ). Oosporangia up to 230 µm long, 190 µm wide; coronula up to 18 µm high, 6 or 7 helical stripes ( Fig. 10 g ). Oospores 200 µm long × 170 µm wide with 6 or 7 striae of thick ridges; the striae uniting in a small apical crest ( Fig. 10 h ). Oospore membrane shallowly reticulate with (0–)1–2 smooth meshes across the fossa ( Fig. 10 i ).

Antheridia up to 450–470 µm in diameter. Chromosome numbers n = 9.

Recognition

A low growing but distinctive shrubby species with somewhat inflated bicellulate dactyls and robust axes, not at all slender. The oospores are distinctively patterned. Nitella tumida Nordst. , which has not yet been found in the Northern Territory, has much more inflated, even spherical dactyls, and slender axes.

Distribution

Northern, arid zone, temporary, usually turbid, claypans and dams.

Etymology

Named for David Mickle who has collected charophytes in the Pilbara.

Specimens examined

WESTERN AUSTRALIA: Koodjeepindawarranna Pool , 19 Aug. 2006, M. T. Casanova t254 ( MEL); Gnalka Gnoona, 19 Aug. 2006, M. T. Casanova t256 ( MEL). Fortescue River at Millstream ( Palm Pool ), 21 Aug. 2006, M. T. Casanova t258 ( MEL); Ethel Creek Claypan, 1 Aug. 2004, D. A. Mickle & M. N . Lyons 3073 ( PERTH); Cooliarin Pool T1 , 18 May 2004, M. N. Lyons & D. A . Mickle 3063 ( PERTH) . NORTHERN TERRITORY: Jimmy Dam , 23 km ESE Erldunda Homestead, 26 June 2000, P. K. Latz 16363 (DNA) .

Figures

Fig. 10. Nitella micklei (a, b) from P.K.Latz 16363 (DNA), (c–g) from holotype specimens M.T.Casanova PBS17: r114 (MEL), (h, i) from M.N.Lyons & D.A.Mickle 3063 (PERTH). (a) Three whorls of branchlets, scale: 1 cm. (b) Single whorl of antheridial branchlets, scale: 1 mm. (c) Sterile branchlet whorl, scale: 5 mm. (d) Fertile branchlet whorl, scale: 1 mm. (e) Apex of fertile branchlet, scale: 1 mm. (f) Fertile female branchlets with oogonium, scale: 1 mm. (g) Oogonium with 5 or 6 convolutions, scale: 100 µm. (h) Scanning electron microscope (SEM) image of oospore, scale: 50 µm. (i) SEM image of detail of the reticulum of the oospore wall, scale: 2 µm.