Achnanthidium kangdingnese P. Yu, Q.M. You & Q.X. Wang, 2022

Yu, Pan, You, Qingmin, Bi, Yonghong & Wang, Quanxi, 2022, A new freshwater species Achnanthidium kangdingnese (Bacillariophyta, Achnanthidiaceae) from Sichuan Province, China, PhytoKeys 204, pp. 97-108 : 97

publication ID	https://dx.doi.org/10.3897/phytokeys.204.89690
persistent identifier	https://treatment.plazi.org/id/48CB6B8D-B057-5D41-813D-25C10FF686C3
treatment provided by	PhytoKeys by Pensoft
scientific name	Achnanthidium kangdingnese P. Yu, Q.M. You & Q.X. Wang
status	sp. nov.

Treatment

Achnanthidium kangdingnese P. Yu, Q.M. You & Q.X. Wang sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5

Description.

LM observations (Fig. 1A View Figure 1 -AD), valves are linear in shape, with rounded apices. Some individuals were slightly constricted in the middle. Valve length 10.8-23.5 µm, breadth 3.8-4.0 µm (n = 200). On both valves striae are radiate throughout, and striae count cannot be performed with LM. Raphe valve is concave, with a narrow, linear axial area slightly expanded near the center. The central area is well defined with one or two spaced striae. Rapheless valve is convex, with a narrow linear axial area weakly expanded at the middle portion of the valve. The central area is a small oval or absent.

SEM observations (Figs 2 View Figure 2 - 5 View Figure 5 ), both valves have a narrow hyaline area at the valve face-mantle junction (Figs 2A, B View Figure 2 , 4A, B View Figure 4 ). Raphe valve: Externally, the raphe is filiform and straight (Fig. 2A, B View Figure 2 ), distal raphe ends are deflected in opposite directions (Fig. 2 A-D View Figure 2 ), and proximal raphe ends are straight and teardrop-shaped (Fig. 2A, B, E View Figure 2 ). The number of striae is 34-36 in 10 µm at the middle portion, and 33-38 in 10 µm near the apices (Figs 2A, B View Figure 2 ; 3A View Figure 3 ). Areolae are round or oval. The uniseriate striae are composed of 4-7 areolae in the middle portion of the valve (Fig. 2A, B, E View Figure 2 ), and 1-7 areolae at the apex (Fig. 2 A-D View Figure 2 ). Valve mantle with a single row of linear areolae extend around the apices with a small interruption at the ends (Fig. 2A, C-E View Figure 2 ). Internally, the thickening widens at the end (Fig. 3A, C View Figure 3 ), and the raphe terminates in raised helictoglossae close to the apices (Fig. 3A-C View Figure 3 ). Proximal raphe ends are distinctly deflected in opposite directions (Fig. 3B, E View Figure 3 ). Areolae are transapically elongated in throughout valve (Fig. 3C, E View Figure 3 ). Areolae are occluded by hymene perforated by delicate slits, and each hymen is closely joined with the adjacent hymen (Fig. 3D View Figure 3 ).

Rapheless valve: the single row of pores on the mantle is continuous (Figs 4A-C View Figure 4 , 5A, C View Figure 5 ). Externally, the axial area is linear and weakly expanded in the central area (Fig. 4A, B View Figure 4 ). On some valves, there are two slit-like areolae oriented longitudinally in the middle region of the axial area (Fig. 4B View Figure 4 ). Striae are uniseriate, comprised of 3-6 round or transapically oriented areolae in the central area (Fig. 4A, B, D View Figure 4 ), and 1-5 round or oblong areolae at the apices (Fig. 4A-C View Figure 4 ). A row of slit-like areolae is present on the mantle (Fig. 4A, B View Figure 4 ). Internally, the axial area is slightly raised (Fig. 5A View Figure 5 ). Areolae are transapically oval in the valve (Fig. 5B, C View Figure 5 ). The number of striae is 34-38 in 10 µm in the center, and 38-40 in 10 µm near the apices (Figs 4A, B View Figure 4 ; 5A View Figure 5 ). Areolae are occluded by hymens perforated by delicate slits, and each hymen is closely joined with an adjacent hymen (Fig. 5B, C View Figure 5 ).

Holotype (designated here).

SHTU! Slide MGC201508036 in Lab of Algae and Environment, College of Life Sciences, Shanghai Normal University, Shanghai, China. Holotype illustrated in Fig. 1D, R View Figure 1 .

Type locality.

China. Mugecuo lake, Sichuan Province, 30°08'43"N, 101°51'35"E, altitude: 3780 m, leg. Quanxi Wang in August 2015.

Etymology.

The species so named refers to Kangding County where the holotype was collected.

Ecology.

Periphytic diatom samples collected in Mugecuo Lake (MGC201508036), pH 7.8, water temperature 12.5 °C, Conductivity 35 μs.cm-1). The sample of this new species occurred at less than 2% relative abundance (total counted 400 valves). There are 5 species that accounted for more than 5% of sample MGC201508036: Pantocsekiella ocellata (Pantocsek) K.T. Kiss & E. Ács ( Ács et al. 2016) (47.5%), Brachysira blancheana H. Lange-Bertalot & G. Moser ( Lange-Bertalot and Moser 1994) (9.6%), Encyonema silesiacum (Bleisch) D.G. Mann ( Round et al. 1990) (7.3%), Staurosira pseudoconstruens (Marciniak) H. Lange-Bertalot ( Krammer and Lange-Bertalot 2000) (7.1%), and Nitzschia frustulum ( Kützing) A. Grunow ( Cleve and Grunow 1880) (5.2%).

Distribution.

The new species is known only from the type locality.