Ulnaria constricta-biseriata Bing Liu, 2023

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

publication ID	https://dx.doi.org/10.3897/phytokeys.228.101080
persistent identifier	https://treatment.plazi.org/id/67A4AC44-FDA2-54DD-AFE1-BC094E02D77A
treatment provided by	PhytoKeys by Pensoft
scientific name	Ulnaria constricta-biseriata Bing Liu
status	sp. nov.

Treatment

Ulnaria constricta-biseriata Bing Liu sp. nov.

Figs 14 View Figure 14 , 15 View Figure 15 , 16 View Figure 16 , 17 View Figure 17 , 18 View Figure 18

Holotype.

Slide JIUDIA202301, specimen circled on slide, illustrated as Fig. 14A View Figure 14 .

Registration.

PhycoBank http://phycobank.org/103807

Type locality.

China. Guizhou province: Fanjing Mountain, Temple Longquan, Heiwan River (27°51'36"N, 108°45'51"E, 532 m a.s.l.), collected by Bing Liu, December 31, 2015.

Description.

LM (Fig. 14 View Figure 14 ). Valves linear-lanceolate, constricted at centre, apex rostrate to sub-capitate (Fig. 14A-H View Figure 14 , see also Figs 16A View Figure 16 , 17A View Figure 17 , 18A, E View Figure 18 ). Valve dimensions (n = 35): length 66-166 μm, width 5.5-8 μm at constricted centre, narrower by 0.2-1.1 µm than at its widest. Valve margins parallel with rostrate to sub-capitate apices (Fig. 14A-H View Figure 14 ). Sternum central, distinct, extending whole length of valve. Rectangular or square central area. Ghost striae often present in central area (e.g., Fig. 14A-E View Figure 14 ). Striae parallel, radiate only at the poles. Striae mostly opposite one another across sternum. Stria density 10-12 (often 11) in 10 μm.

SEM (Figs 15 View Figure 15 - 18 View Figure 18 ). Frustule in girdle view rectangular (Fig. 15A View Figure 15 ). Epivalve with up to three closed copulae (Fig. 16B-F View Figure 16 ), 2nd and 3rd copulae bearing two rows of poroids (2nd = B2, Fig. 15B-E View Figure 15 , white wavy arrow; 3rd = B3, Fig. 15D, E View Figure 15 , black arrow). Valvocopula closed, surrounding whole valve margin (Fig. 16A View Figure 16 ), bearing a mostly continuous row of poroids at the midline, dividing pars interior from pars exterior (Fig. 16B-D View Figure 16 ), lacking ornamentation at both poles (Fig. 16C, D View Figure 16 ); its advalvar edge having a row of serrated projections, each corresponding to a virga internally (Fig. 16B-D View Figure 16 , two arrows respectively). Valve central area rectangular (Figs 17B, E View Figure 17 , 18B, F View Figure 18 ). Striae constructed from series of relatively wide virgae interconnected with thin viminules, closing plates present with a few struts, affixed to the areolar wall (Figs 17B-F View Figure 17 , 18B-D, F View Figure 18 ; closing plate see Fig. 17F View Figure 17 , wavy arrow). Valves with mixed striae, mostly biseriate, formed by viminules; each stria situated opposite each other across sternum, equidistant until radiate at poles, and becoming uniseriate near sternum (Figs 17B-F View Figure 17 , 18B-D, F View Figure 18 ). One rimoportula present at each pole, externally expressed as a simple hole (Fig. 17D, F View Figure 17 ), internally bilabiate, situated close to sternum (Fig. 18C, D View Figure 18 ). Apical pore fields ocellulimbus, consisting of ca. 23 pervalvar and 11 transverse rows of porelli (both pervalvar and transverse rows unequal in length). A few serrated apical outgrowths protruding over each ocellulimbus (Fig. 17C, D, F View Figure 17 , one arrow respectively).

Etymology.

The specific epithet is formed from two terms: constrict and biseriate, reflecting the constricted valve central margins and the mostly biseriate striae of the valve.

Ecology and distribution.

The sampling site is close to the headwaters of the Heiwan River, which originates in the Fanjing Mountain National Nature Reserve. The diatom samples were scraped off of the stone surfaces. The following environmental parameters were measured in the field. Conductivity was 49.7 ± 0.2 μS ∙cm-1, pH was 7.7 ± 0.1 and water temperature was 9.4 ± 0.1 °C. So far, its distribution is known only from the type locality. To sum up, U. constricta-biseriata lives on the stone surfaces of the headwaters of a mountainous river.

Discussion.

Ulnaria constricta-biseriata is characterized by its linear-lanceolate valve outline, constricted valve central margins, and mostly biseriate striae. Ulnaria contracta ( Østrup) E.A. Morales & M.L. Vis has also constricted valve central margins, but it differs from U. constricta-biseriata by its lanceolate valve outlines and mostly uniseriate striae (see Morales et al. 2007, p. 61, figs 48-55, p. 63, figs 56-61, as Synedra ulna var. contracta Østrup).