Ulnaria jishou-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/A7A935AD-ABDF-5126-AC85-0B9FFB073B15
treatment provided by	PhytoKeys by Pensoft
scientific name	Ulnaria jishou-biseriata Bing Liu
status	sp. nov.

Treatment

Ulnaria jishou-biseriata Bing Liu sp. nov.

Figs 19 View Figure 19 , 20 View Figure 20 , 21 View Figure 21 , 22 View Figure 22 , 23 View Figure 23 , 24 View Figure 24 , 25 View Figure 25

Holotype.

Slide JIUDIA202302, specimen circled on slide, illustrated as Fig. 20D View Figure 20 .

Registration.

PhycoBank http://phycobank.org/103808.

Type locality.

China. Hunan province: Jishou City, Lianaiqiao, Donghe River (28°18'51.3"N, 109°43'41.6"E, 200 m a.s.l.), collected by Bing Liu, December 9, 2016.

Description.

LM (Figs 19 View Figure 19 , 20 View Figure 20 ). Frustules rectangular in girdle view (Figs 19A, B View Figure 19 , 20A View Figure 20 ), lanceolate in valve view (Fig. 19C, D View Figure 19 ). Chloroplasts two long plates per cell, valve-appressed (Fig. 19A View Figure 19 ), covering large portion of valve face in valve view (Fig. 19C, D View Figure 19 ). Valves lanceolate with prolonged, rostrate poles (Fig. 20B-J View Figure 20 , see also Figs 23A View Figure 23 , 24A View Figure 24 , 25A View Figure 25 ), dimensions (n = 38): length 139-200 μm, width 6-8 μm at centre. Valve margins parallel near central area, gradually tapering towards rostrate poles (Fig. 20B-J View Figure 20 ). Sternum central, distinct, narrow, regular. Central area having three arrangements: extending towards both margins forming square to rectangular (Fig. 20B, J View Figure 20 ) or round hyaline space (Fig. 20C-E View Figure 20 ); extending to one margin with other margin flanked by few short striae (Fig. 20G-I View Figure 20 ); both margins bordered with few short striae (Fig. 20F View Figure 20 ). Ghost striae sometimes present (e.g., Fig. 20C, I View Figure 20 ) in central area. Striae parallel, radiate only at poles, and mostly opposite one another across sternum. Stria density 10-12 (often 11) in 10 μm.

SEM (Figs 21 View Figure 21 - 25 View Figure 25 ). In some dividing cells, both epivalve and hypovalve associated with valvocopula and two copulae, forming 3:3 configuration of girdle bands (Fig. 21A-F, bands View Figure 21 labelled B1-B3, B1 = valvocopula); sometimes epivalve associated with valvocopula and three copulae, whereas hypovalve associated with valvocopula and two copulae, forming 4:3 configuration (Fig. 22A-D View Figure 22 ). Copulae sometimes bearing two rows of poroids near poles (Fig. 21C-F View Figure 21 ). Valvocopula a closed hoop, same shape as valve outline, closely attached to mantle interior, surrounding the valve internal margin (Fig. 23A View Figure 23 ); bearing a mostly continuous row of poroids dividing pars interior from pars exterior located at midline (Fig. 23B-E View Figure 23 ), some isolated poroids visible in pars exterior (Fig. 23B View Figure 23 , two arrows). At the advalvar edge, valvocopula produces a row of serrated projections, each corresponding to a virga internally (Fig. 23C View Figure 23 , arrows). Valvocopula lacking ornamentation at both poles (Fig. 23D, E View Figure 23 , black arrow respectively). Striae continuing onto mantle, absent from centre (Fig. 24B View Figure 24 ). Valve face and mantle intersecting almost at a right angle (Fig. 24B-F View Figure 24 ). Valve characterized by relatively wide virgae, interconnected with thin viminules, and closing plates with few struts fixing them onto each areolar wall (Fig. 24C, D View Figure 24 ). Valve has 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 are distributed on most of the valve face except each apex, and the other composed of a uniseriate main part and a biseriate minor part, which are only present near each apex (Figs 24C, D View Figure 24 , 25B-F View Figure 25 ). Ocellulimbus composed of ca. 18 pervalvar and 10 transverse rows of porelli (both pervalvar and transverse rows unequal in length). A few serrated apical outgrowths protruding over each ocellulimbus (Fig. 24C View Figure 24 , three arrows). Internally, virgae transversely extending towards mantle from sternum. Striae situated almost opposite each other across sternum and becoming uniseriate near sternum (Fig. 25B-F View Figure 25 ). Central area with three arrangements: extending to one margin, bordering with several short striae (Figs 24B View Figure 24 , external, 25E, internal); bordering both margins with several short striae (Figs 24E View Figure 24 , external, 25F, internal); or extending to both margins forming transapically rectangular fascia (Figs 24F View Figure 24 , external, 25B, internal). One rimoportula at each pole (Figs 23D, E View Figure 23 , 24C, D View Figure 24 , 25D View Figure 25 ), occasionally two produced at an apex (Fig. 25C View Figure 25 ). External opening of rimoportula expressed as a simple hole with different shapes (Fig. 24C, D View Figure 24 ); internally bilabiate, situated close to sternum, aligned with striae (Fig. 25C, D View Figure 25 ).

Etymology.

The epithet jishou-biseriata is formed from the city name Jishou and the term biseriate to reflect its type locality (Jishou) and its mostly biseriate striae.

Ecology and distribution.

The sampling site is close to Jishou City and many anthropogenic influences affect the environment and hence the diatoms. The diatom samples were scraped off of the stone surfaces. The following environmental parameters were measured in the field: Conductivity was 202.3 ± 1.2 μS ∙cm-1, pH was 8.5 ± 0.1, and water temperature was 13.2 ± 0.3 °C. So far, its distribution is known only from the type locality. To sum up, U. jishou-biseriata lives on the stone surfaces of a mountainous river running through a small city.

Discussion.

Ulnaria jishou-biseriata is characterized by its lanceolate valve outline, mostly biseriate striae, and very variable central areas. With respect to the valve outline, it is similar in some ways to U. ulnabiseriata , but the former has smaller and very variable central areas whereas the latter’s central areas are always a rectangular fascia (see Liu et al. 2017, p 249, figs 30-35).