Surirella ectorii Bing Liu & Rioual sp. nov.

Figs 4, 5, 6

Holotype.

Specimen circled on slide DIA 2025001 (= Fig. 4 B), deposited in the Herbarium of Jishou University (JIU), China. Registration: http://phycobank.org/105636.

Type locality.

China. Qinghai Province, Lake Qinghai, a sampling site near the lakeshore, 36 ° 50 ' 34 " N, 99 ° 42 ' 39 " E, 3210 m asl., collected by Bing Liu, July 19 th, 2019.

Description.

LM (Fig. 4). Valve outlines nearly elliptical with almost isopolar headpole and footpole. Valve dimensions (n = 24): length range 44–69 μm, width range 34–45 μm at its widest region. Costa-stria bundles (CSBs) distinct, alternating with over-fibula ribs (OFRs) from pole to pole (labelled in Fig. 4 E). CSBs radiate throughout the valve surface. Fibulae visible, short (judged by OFRs, labelled in Fig. 4 E), 4–6 in 10 μm. A marginal row of costae produced on the wall of raphe canal (e. g., Fig. 4 B, arrows), 16–18 in 10 μm.

SEM (Figs 5, 6). Externally, raphe canal located directly on mantle (Fig. 5 A – C), and wall of raphe canal bearing a marginal row of costae (Fig. 5 C, arrows, Fig. 5 F, double-headed arrow). Distal raphe endings straight, interrupted at both headpole and footpole (Fig. 5 D, E). Surface costae mostly slightly raised, some reaching valve midline (Fig. 5 C). Each CSB often composed of ca. 2–5 costae and 3–6 striae (Fig. 5 F). Outside openings of areolae slit-like (Fig. 5 F). Striae multiseriate, composed of ca. 2–5 rows of areolae (Figs 5 F, 6), 15–19 in 10 μm (measured at the valve margin from SEM images, n = 3). Surface siliceous warts and reticulate thickenings produced on costae and between adjacent two costae, respectively (e. g., Fig. 5 D – F). Internally, wall of raphe canal slightly growing into cell cavity, whereas portulae visible (Fig. 6 A, B). Fibulae slim, short, sometimes doubled or tripled (Fig. 6 F, arrows), spanning ca. 1 / 4 of valve width, not extending to valve midline except at two poles. Marginal trough-like depressions present around entire raphe canal (Fig. 6 D, black dotted line). Raphe continuous at headpole (Fig. 6 C, arrow) whereas interrupted at footpole (Fig. 6 D, two arrows). 2–5 portulae produced between two adjacent fibulae (Fig. 6 F, arrows). Inner openings of areolae rounded, not rimmed.

Etymology.

Named after the late diatomist from Luxembourg, Luc Ector (1962–2022), for his dedication to diatom taxonomy and his help with our studies of diatoms in China.

Vernacular name.

The Chinese name is “ 埃氏双菱藻 ”.

Ecology and distribution.

Surirella ectorii was commonly found on the sediment at the surface of the stones collected in Lake Qinghai but not in large abundance. In the samples it is found in association with S. brightwellii. So far, S. ectorii has only been found in the type locality and may therefore be considered as a brackish diatom endemic to Lake Qinghai.