Ulnaria menyuanensis Bing Liu, 2023

Liu, Bing, 2023, The diatom genus Ulnaria (Bacillariophyta) in China, PhytoKeys 228, pp. 1-118 : 1

Ulnaria menyuanensis Bing Liu sp. nov.

Figs 44 , 45 , 46 , 47

Holotype.

Slide JIUDIA202307, specimen circled on slide, illustrated as Fig. 44D .

Registration.

PhycoBank http://phycobank.org/103813

Type locality.

China. Qinghai province: Menyuan County, an unnamed river, at a sampling location named Kengtan (37°27'28"N, 101°23'15"E, 2940 m a.s.l.), collected by Bing Liu, July 18, 2019.

Description.

LM (Fig. 44 ). Valves lanceolate (fusiform) with cuneate to rostrate apices (Fig. 44A-J , see also Figs 45A , 46A ). Valve dimensions (n = 31): length 60-104 μm, wide 5-7 μm at centre. Sternum distinct, extending length of valve. Central area not clearly visible due to presence of many ghost striae (Fig. 44A-J , see also Figs 45B, E, F , 46B, E, F ). Striae parallel, radiate only approaching each pole, 12-14 in 10 μm, denser near poles. Striae on both sides of sternum, some alternate, some opposite.

SEM (Figs 45 - 47 ). Valve characterized by a series of relatively wide virgae, interconnected with vimines and closing plates affixed with a few struts to each areolar wall (Figs 45A-F , 46A-F , closing plate see Fig. 47D, F ). Central area circumscribed by both short marginal striae and isolated areolae (Figs 45B, E, F , 46B, E, F ). Unperforate internal shallow grooves distinct in central area (e.g., Fig. 46B, E, F ). Ocellulimbus composed of ca. 13 pervalvar and 7 transverse rows of porelli. Striae uniseriate. Areolae not apically elongated from sternum to mantle (Fig. 46B-F ). One rimoportula located at each pole, externally expressed as a simple hole (Fig. 45C, D ), internally bilabiate, situated close to sternum (Fig. 46C, D ). Valvocopula a closed hoop, surrounding the valve internal margin (Fig. 47A ). Valvocopula bearing a mostly continuous row of poroids dividing pars interior from pars exterior, located at midline (Fig. 47B, C, E ), lacking ornamentation at both poles (Fig. 47D, F ). On its advalvar edge, valvocopula has a row of serrated projections, each corresponding internally to a virga (Fig. 47B, C, E , three arrows, respectively).

Etymology.

Named after Menyuan County, where the species was found.

Ecology and distribution.

Ulnaria menyuanensis was commonly found in the surface sediment collected in Kengtan with U. blancoi . Thus, U. menyuanensis lives on the stone surfaces of a plateau river. So far, its distribution is known only from the type locality.

Discussion.

Ulnaria menyuanensis is characterized by its fusiform valve outline, the presence of distinct ghost striae, and cuneate to rostrate apices. It differs from U. ramesii ( Héribaud) T. Ohtsuka by the latter’s linear-lanceolate valve outline (see Morales et al. 2007, p. 73, figs 87-94, as Synedra ulna var. ramesi ) and differs from U. oxyrhynchus ( Kützing) Aboal by the latter’s acute apices (see Morales et al. 2007, p. 65, figs 62-67, as Synedra ulna var. oxyrhynchus ). Ulnaria verhaegeniana Van de Vijver, De Haan, Mertens & Cocquyt has parallel margins almost to valve apices while U. menyuanensis has lanceolate valve outline and possesses distinct ghost striae (see Van de Vijver et al. 2017, p. 222 for comparison).

Figures

Figure 44. Ulnaria menyuanensis sp. nov., x 1000, LM A-J ten valves exhibiting a size diminution series, note the lanceolate valve outline and distinctive ghost striae in the middle regions of the valves D micrograph of holotype specimen. Scale bar: 10 μm.

Figure 45. Ulnaria menyuanensis sp. nov., external view, SEM A a complete valve B middle part detail from A, note the shallow grooves and short striae at the central region C, D two apical details from A. E, F Other middle parts, note the shallow grooves and short striae. Scale bars: 10 μm (A); 2 μm (B-F).

Figure 46. Ulnaria menyuanensis sp. nov., internal view, SEM A a complete valve B middle part from A, note shallow grooves and short striae C, D two apical details from A, note the bilabiate rimoportulae and apical pore fields E, F other middle parts, note shallow grooves and short striae. Scale bars: 10 μm (A); 2 μm (B-F).

Figure 47. Ulnaria menyuanensis sp. nov., internal view, SEM A a valve with associated valvocopula B middle part detail from A, note serrated projections (three arrows) C, D apical details from A, note serrated projections (C, three arrows) and closing plates (D, two arrows) E, F details from other apex from A, note serrated projections (E, three arrows) and closing plates (F, two arrows). Scale bars: 10 μm (A); 5 μm (B, C, E); 2 μm (D, F).