Ulnaria pandurata-biseriata Bing Liu, 2023

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

Ulnaria pandurata-biseriata Bing Liu sp. nov.

Figs 26 , 27 , 28 , 29

Holotype.

Slide JIUDIA202303, specimen circled on slide, illustrated as Fig. 26C .

Registration.

PhycoBank http://phycobank.org/103809

Type locality.

China. Hunan province: Zhangjiajie National Forestry Park, Jinbian stream, at Shuirao Simen (29°20'36"N, 110°28'13"E, 467 m a.s.l.), collected by Bing Liu, December 29, 2015.

Description.

LM (Fig. 26 ). Valves panduriform with slightly constricted middle part and rostrate poles (Fig. 26A-P , see also Figs 27A , 28A , 29A ). Valve dimensions (n = 36): length 37-60 μm, width 7-9.5 μm at centre, 8-10 μm at widest part. Sternum distinct, extending length of valve. Central area has two arrangements: an asymmetric hyaline region extending to both margins (Fig. 26A-M ) or a hyaline area which extends to one margin with the other side bordered with a few short striae (Fig. 26N-P ). Ghost striae are sometimes present (e.g., Fig. 26D, K ) in the central area. Striae parallel, radiate only approaching each apex, and mostly opposite one another across sternum. Striae density 9-11 (often 10) in 10 μm.

SEM (Figs 27 - 29 ). Valve characterized by relatively wide virgae, interconnected with thin viminules, areolar closing plates having a few struts fixing them onto the areolar wall (Figs 27A-F , 28A-F , 29A-D ). Valve with two types of mixed striae: one composed of a biseriate main part and a uniseriate minor part near sternum (usually 1 or 2 areolae), which describe most striae of valve (Figs 27A-F , 28A-F ), and the other composed of a biseriate part, a triseriate part, and a uniseriate part near sternum (usually 1 or 2 areolae) (Figs 27C, D , 28B-F , two arrows, respectively). One rimoportula present at each pole, externally expressed as a simple hole (Fig. 27C, D, F ), internally bilabiate, situated close to sternum (Fig. 28C-F ). Ocellulimbus composed of ca.19 pervalvar and 9 transverse rows of porelli. A few serrated apical outgrowths protruding over the ocellulimbus (Fig. 27F ). Valvocopula is a closed hoop, attached to the mantle interior, surrounding internal valve margin (Fig. 29A ). Each valvocopula bears a mostly continuous row of poroids dividing the pars interior from pars exterior, located at the midline (Fig. 29A-D ); lacking ornamentation at either apex (Fig. 29C, D ). On its advalvar edge, valvocopula bears a row of serrated projections, each corresponding internally to a virga (Fig. 29C, D , three arrows respectively).

Etymology.

The epithet pandurata-biseriata is a combination of the terms pandurate and biseriate to reflect the valvar panduriform outline of the valve and its mostly biseriate striae.

Ecology and distribution.

The sampling site is situated close to the headwaters of Jinbian stream, which originates in the Zhangjiajie National Forestry Park. The diatom samples were scraped off of stone surfaces. The following environmental parameters were measured in the field: Conductivity was 102.7 ± 0.8 μS ∙cm-1, pH was 8.5 ± 0.7 and water temperature was 8.7 ± 0.2 °C. So far, its distribution is known only from the type locality. To sum up, U. pandurata-biseriata lives on the stone surfaces of the headwaters of a mountainous stream.

Discussion.

Ulnaria pandurata-biseriata is characterized by its panduriform valve outline, mostly biseriate striae, variable central areas, and smaller valves. Similar taxa include U. goulardii D.M. Williams, Potapova & C.E. Wetzel (see Williams 1986, p. 141, figs 27-36) and U. sangzhi-biseriata sp. nov (see below). All possess mostly biseriate striae, but they can be distinguished by the panduriform valve outline of U. pandurata-biseriata from the two latter’s lanceolate valve outline (for U. goulardii , see Williams 1986, p. 141, figs 27-36, as Synedra goulardii ).

Figures

Figure 26. Ulnaria pandurata-biseriata sp. nov., x 1000, LM A-P 16 valves exhibiting a size diminution series, note the panduriform valve outline and variable central areas C micrograph of holotype specimen. Scale bar: 10 μm.

Figure 27. Ulnaria pandurata-biseriata sp. nov., external view, SEM A a frustule in valve view B middle part detail from A, showing the central area with a few shortened marginal striae on one side C, D two apical details from A, note some partially triseriate striae (arrows) E another middle part showing the fascia-shaped central area F another apex, note a few serrated projections protruding over ocellulimbus. Scale bars: 10 μm (A); 2 μm (B-F).

Figure 28. Ulnaria pandurata-biseriata sp. nov., internal view, SEM A a complete valve B-D details from A, note some partially triseriate striae (arrows) E, F other apical details, note partially triseriate striae (arrows). Scale bars: 10 μm (A); 2 μm (B-F).

Figure 29. Ulnaria pandurata-biseriata sp. nov., internal view, SEM A a valve with a valvocopula B middle detail from A, note the unornamented middle portion of valvocopula (arrow) C, D apical details from A, note serrated projections over each virga (arrows) and valvocopula without ornamentation at each apex. Scale bars: 10 μm (A); 2 μm (B-D).