Tolypella mongolica R.E. Romanov, V.S. Vishnyakov, V.Yu. Nikulin & A.A. Gontcharov

Romanov, Roman E., Nikulin, Vyacheslav Yu., Vishnyakov, Vasily S., Tsegmid, Bukhchuluun, Efremov, Andrey N., Zhakova, Liubov V. & Gontcharov, Andrey A., 2024, Tolypella mongolica (Charophyceae, Characeae): A new dioecious charophyte species from the center of Eurasia and implications for charophyte taxonomy, including the validation of T. porteri and the new combination for T. jwalae, Phytotaxa 659 (1), pp. 24-40 : 27-29

Tolypella mongolica R.E. Romanov, V.S. Vishnyakov, V.Yu. Nikulin & A.A. Gontcharov sp. nov.

Diagnosis:— T. mongolica sp. nov. differs from all species of Tolypella but T. hispanica Nordst. ex Allen (1888: 51) and T. porteri ( Daily 1954: 144) R.E. Romanov stat. et comb. nov. (this study, see below) by dioecy. Ripe oospores of T. mongolica sp. nov. differ from all species of this genus in the most complex sculpture of surface resembling an aerial view of a mountainous landscape or being coarsely tuberculate. T. mongolica sp. nov. is distinct in rbc L and ITS rDNA sequences from all species of Tolypella . T. mongolica sp. nov. differs from dioecious T. hispanica by the absence of a densely reticulated oospore surface. T. mongolica sp. nov. differs from dioecious T. porteri by the following traits: branchlet end cells are not reduced and not sharply narrower than penultimate cells, flanges of spiral ribs are not poorly developed, the oospore surface is not smooth to very finely granulate.

Description ( Figs. 1–46 ):—Dioecious (female only) plants are dark green, without lime incrustation in a brackish environment but with evident incrustation in less brackish habitat, up to 10 cm high, reaching up to 13 cm in spawn if plants are spread for pressing at sheet ( Fig. 1 ). The protonema can persist and is easily recognizable because of its thickness and length resulting in a robust appearance. The internodes and branchlets above the first node are progressively shortening toward the apex, but branchlets are always clearly much longer than the internodes. This results in largely overlapping branchlet whorls especially at the shoot apices ( Figs. 1–7 ). No sterile branchlets are found. The first node produces numerous fertile branchlets, up to 12 (and more?), and shoots ( Fig. 11 ). The branchlets are monopodial, i.e. having the main axis bearing a single node mostly placed closer to the branchlet base because of the more or less shortened basal internode of the branchlet. The length of the basal internode of branchlets sharply shortens from basal to apical axial nodes, being the longest and clearly visible at branchlets at the basal node of each plant ( Figs. 8–12, 15–20 ). The end of the main axis of the branchlet is 3-celled ( Fig. 14 ), 2-celled as an exception, with the longest basal cell being more than half of the end ray of the branchlet. Branchlet nodes bear three lateral rays, incl. single abaxial ones, always distinctly many times shorter than the branchlet main axis, frequently barely recognizable to almost invisible in dense clusters of oogonia ( Fig. 21 ). The rays are 3-celled, rarely 2-celled, with progressively decreasing length of subsequent cells. Lateral rays can be with a single fertile node each bearing three subsequent lateral rays too ( Figs. 10, 22 ). The main axes of branchlets and lateral rays are gradually narrowing to the ends, although sometimes the difference between subsequent cells in width in case of short branchlets and 2-celled rays is spottable too. End cells are always with narrow to very narrow rounded, but not pointed tips ( Figs. 12–14, 20 ), short, but not tiny at long branchlets, rarely appearing somewhat mucronate in pressed state. Numerous oogonia (up to several dozen) are formed at axial nodes inside and outside of the whorls as well as at single nodes of each branchlet ( Figs. 2–13, 15–22 ). Dense placement of oogonia at axial nodes and nodes of branchlets of the same whorl, close to axial nodes because of shortened basal rays of branchlets results in the false appearance of heads at first glance, although whole branchlets are not shortened. Oogonia are ellipsoid, numerous, densely clustered at the bases of whorls and branchlet nodes, sessile or at stalks up to 450 μm long, 360–530 μm long excl. coronula, 350–475 μm wide. Spiral cells form 7–9 convolutions; they are not swelling below the coronula, but as a really rare exception can be narrowing and extending in the shape of the cone below the coronula. Coronulae are hemispheric to widely conical with blunt tips, 33–45 (as an exception 53) μm long, 60–78 μm wide, consisting of cells with more or less equal length or slightly longer in the upper row and vice versa. Oospores are widely obovoid, with a widely rounded apical pole ( Figs. 23–28 , 38–42 ), which is sometimes concave inside the oospore in a dry state, narrowing to the base, yellow-brown in an unripe state, dark brown to almost black in the ripe state in reflected light, red-wine-reddish to brown in the ripe state in transmitting light, with 6 to 7 flanged ribs and well-developed flanges around basal plates, 230–340 μm long, 220–330 μm wide, sparsely coarsely tuberculate to having the appearance of an aerial view of a mountain landscape with acute to mostly sharp edges of elements at the ripest stage ( Figs. 23–46 ). The presence of isolated well-developed pointed protrusions is notable too ( Figs. 32–34 ). They are more acute and elongated in comparison to tubercles, conical or tubercle-like at the base, forked into 2 or 3 to several moderately divergent narrow acute endings. Male plants were not found.

Holotype (designated here):— MONGOLIA, Khövsgöl Aimag, Tsagaan-Uul Sum, endorheic brackish lake Gashuun Nur , 49°27.541′N, 98°31.990′E, ca. 1870 m a.s.l., down to 0.6 m depth, on silt, abundant, 17 July 2015, Vishnyakov X-55, det. Romanov (UBA-6283) ( Fig. 1 , upper bigger plant).

Isotypes (designated here):—UBA-6283, LE A 0006499, IBIW 66762, NHMM 21575.

Paratypes:— RUSSIAN FEDERATION, Altai Republic, Kosh-Agach District, channel between temporary small brackish lakes, [~ 49°58’39”N 88°44’01”E], on 0–0.2 m depth, on sand with coarse detrital sludge, 17 July 2016, Efremov, det. Romanov ( LE A 0006500). GenBank accession: rbc L PP 582210. RUSSIA, Volgograd Region, Pallas District, near southern shore of Lake Bulukhta, shallow bitter water body, [~ 49.295N, 46.104E], 03 June 1990, Klinkova & Shantser, det. Romanov & Zhakova ( LE A 0006501). GenBank accessions: rbc L PP 582211, ITS PP 583570.

Representative DNA sequences for LE:— rbc L PP 582212, ITS PP 583571.

Type locality:— MONGOLIA, Khövsgöl Aimag, Tsagaan-Uul Sum, endorheic brackish lake Gashuun Nur, 49°27.541′N, 98°31.990′E, ca. 1870 m a.s.l.

Etymology:—This species was named to highlight the country where its type locality is situated. In addition, the surface of ripe oospores resembles an aerial view of a mountain landscape resembling the relief of Mongolia, a beautiful upland and mostly mountainous country.

Distribution:— T. mongolica is known from three localities in Mongolia, the Altai Mountains, and the eastern part of the Lower Volga Region, i.e. in the North Caspian Lowland, only.

Habitat:— T. mongolica thrives in the shallows (0–0.6 m) of small brackish lakes and channels with the variable water levels in midland steppe and lowland steppe at hyper-continental and continental climates, on silt and sand with coarse detrital sludge.

Figures

FIGURE 1. Holotype and isotypes of Tolypella mongolica sp. nov., Mongolia (UBA-6283). The upper bigger plant is a holotype. Scale: 2 cm. Photograph by R.E. Romanov.

FIGURES 2–22. Morphological traits of Tolypella mongolica sp. nov., Mongolia (UBA, LE, NHMM): 2–5—apical parts of plants with different numbers of more or less compacted branchlets; 6—whorl of most compacted branchlets; 7—lateral branch; 8–10—basal parts of whorls with well-developed branchlets, arrowhead indicates lateral ray with fructifying node; 11—first node (arrowhead) of richly branched plant; 12—close view of apical whorls of branchlets, arrowhead indicates richly fertile single node of main axis of branchlet; 13—apical whorl of branchlets having two-celled ends; 14—gradually tapering three-celled end of long branchlets; 15–20—basal parts of branchlet whorls and axial nodes with numerous oogonia, arrowheads indicate single richly fertile nodes of branchlets above basal branchlet internode having variable length; 21 & 22—richly fertile single nodes of main axes of branchlets: 21—arrowheads indicate lateral rays; 22—arrowheads indicate nodes of lateral rays. Scale: 2–11—5 mm, 12–18, 20–22—1 mm, 19—2 mm. Photographs by R.E. Romanov.

FIGURES 23–28. Oospores of Tolypella mongolica sp. nov., Mongolia (UBA, LE), general appearance with different expression of surface sculpture, scanning electron microscopy: 23–25—lateral view; 26—apical view; 27—basal view; 28—tangential view of basal pole. Scale: 100 μm. Photographs by R.E. Romanov.

FIGURES 29–37. Oospores of Tolypella mongolica sp. nov., Mongolia (UBA, LE), different expression of surface sculpture, scanning electron microscopy: 29 & 30—densely coarsely tuberculate surface; 31—different expression of oospore surface at neighboring fossae, from sparsely weakly tuberculate to having complex tubercles at the middle of fossa; 32 & 33—isolated protrusions with acute forked ends; 34—tuberculate surface and tuberculate surface with forked acute protrusions at neighboring fossae; 35–37—surface resembling an aerial view of a mountain landscape. Scale: 29, 31 & 35—40 μm, 30, 32, 33, 34, 36 & 37—20 μm. Photographs by R.E. Romanov.

FIGURES 38–46. Oospores of Tolypella mongolica sp. nov., Altai Mountains (LE), general appearance and sparsely coarsely tuberculate surface, scanning electron microscopy: 38–42—general appearance: 38, 41 & 42—lateral view of oospores with different degree of prominence of tubercles; 39 & 40—basal view; 43–46—sparsely coarsely tuberculate surface with different prominence of tubercles. Scale: 38–42—100 μm, 43—10 μm, 44–46—20 μm. Photographs by R.E. Romanov.