Nitella crocodylus Casanova & Karol 2023, sp. nov.
Creators: name: Casanova, Michelle T.
name: Karol, Kenneth G.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Charophyta
Charophyceae
Charales
Characeae
Nitella
Nitella crocodylus

description: Nitella crocodylus Casanova & Karol, sp. nov.   
 Type: Manton Dam, 5 Sep. 2010, M. T.Casanova r760 (holo: DNA!; iso: BM!, MEL!, NY!).   
 [Nitella pseudoflabellata f. sonderi auct. non (A.Braun) R.D.Wood: R.D.Wood in R.D.Wood & K.Imahori, Revis. Charac. 1: 589–590 (1965)].   
 [Nitella pseudoflabellata var. imperialis auct. non T. F.Allen: R.D. Wood, Nova Hedwigia 22: 69 (1971)].   
 Dioecious. Plants up to 30 cm high, with some long branchlets along the axis; plant apex with mucus-covered heads (Fig. 6 a, c). Axes 400–500 µm wide; internodes up to 12 cm long in the lower parts, 10–20 mm in the upper parts, approximately as long as the sterile branchlets. Fertile branchlets 6 in a whorl; variable in length, some very short and in contracted whorls, others with very long (6–9 mm) primary branchlet segments; mostly 2× furcate, primary segments 1–9 mm long, secondary segments 4–6, up to 0.5–2 mm long or more if not bearing gametangia, 3–6 tertiary segments (dactyls) up to 0.6 mm long. Sterile branchlets 6 in a whorl, 2× furcate, primary segments 5–15 mm long, secondary segments 3–5, up to 6 mm long but often shorter, tertiary segments (dactyls) 2 or 3, up to 3 mm long (Fig. 6 b). Fertile and sterile dactyls similar, bicellulate, up to 1 mm long, tapering to a conical, acute end-cell (Fig. 6 d). Fertile branchlets often contracted into axial and apical heads (Fig. 6 c). Post-fertile branchlets apparently extend the primary branchlet segment, appearing as little brushes of segments and dactyls at the tips (Fig. 6 e), mucus present around young fertile branchlets. Gametangia on separate plants at all fertile branchlet nodes. Oosporangia solitary, coronula up to 20 µm high, upper cells approximately the same as lower (Fig. 7 f). Oospores dark brown, 270–300 µm long and 240–270 µm wide (Fig. 6 h) with 6 or 7 striae with porous flanges 5–19 μm high and ornamentation in 2 layers; the lower layer perforate with sinuate holes (Fig. 6 g), the upper layer incompletely reticulate, consisting of ropey lines (Fig. 6 i). Basal-cell impressions almost rectangular (Fig. 6 j). Antheridia up to 250 µm in diameter. Chromosome numbers not known.   Recognition  
 This species is characterised by abundant mucus and branchlets with very long primary segments (most likely postreproductive whorls), as well as other, more regularly furcate branchlets. It is distinguished from Nitella oollooensis by the presence in N. oollooensis of central secondary and tertiary branchlet-segment lengths. The oospores are also distinctive.   Distribution  
Water bodies in the vicinity of Darwin.  Etymology  
 This species is in reference to the animal with which the plant coexists in its habitats in the Northern Territory (Crocodylus porosus, the saltwater crocodile). It is a noun in apposition.   Specimens examined  
 NORTHERN TERRITORY: Manton Dam, 5 Sep. 2010,  M. T. Casanova r761 (DNA, MEL); Yirrkala, 19 Aug. 1948,  R. L. Specht A48 (BM, NY); Angularli Creek, Murgenella, 29 Aug. 1987, G. Leach 1397 (DNA, NT)  .
description: Published as part of Casanova, Michelle T. & Karol, Kenneth G., 2023, Charophytes of Australia's Northern Territory - II. Tribe Nitelleae, pp. 322-353 in Australian Systematic Botany 36 (4) on pages 333-335, DOI: 10.1071/SB22029, http://zenodo.org/record/10904369