2 College of Life and Environment Science, Shanghai Normal University, Shanghai 200234, China
Zoigê Wetland covers Maqu County, Hongyuan County and Aba County, and is located at the eastern edge of the Qinghai-Tibet Plateau (Zhou et al., 2002; Chen and Lü, 2010). As typical alpine peat wetland ecosystem, Zoigê Wetland has an important role in biodiversity and the conservation of water and soil. From the mountain regions numerous watercourses flow down towards the wetland, as a consequence forming a complete physiographic region (Mu, 1982).
The diatom genus Muelleria (Frenguelli) Frenguelli was established in 1945 (Frenguelli, 1945), and M. gibbula (O. Müller) Frenguelli is the type species. It comprises a small number of biraphid diatoms, with less than 40 species reported so far. The genus Muelleria is characterized by two apparently longitudinal ribs, the proximal raphe ends deflected to the same direction in external valve (Spaulding and Stoermer, 1997). Most species are restricted to high latitudes of either the southern or northern hemisphere, most are narrowly endemic in fresh water and brackish water (Spaulding et al., 1999).
We encountered a new species of Muelleria from the Zoigê Wetland, and the present report includeslight (LM) and scanning electron microscope (SEM) observations on Chinese specimens of the new species and comparisons with similar species in the genus2 MATERIA AND METHOD
The diatom samples in this study were obtained from Zoigê Wetland in May, 2012. Most of the samples were benthic from freshwater and were fixed in situ with 4% formaldehyde.
Samples were digested with hydrochloric acid and concentrated H2O2 (30%) to remove organic matter. After treatment, cleaned material was washed 5–7 times with distilled water, then dried on cover glasses and mounted in Naphrax.
For LM, the slides were observed with an Olympus BX51 microscope at the University of Colorado, Boulder. For SEM observation, the material was air dried on copper stubs to copper stubs, sputter coated with gold-palladium and viewed with a JEOL JSM-6380LV SEM at Shanghai Normal University.
Type slides and material are stored at the Freshwater Algal Herbarium of Shanghai Normal University(SNU). Terminology for valve features follows Hendey (1964), Round et al. (1990), Spaulding and Stoermer (1997), Spaulding et al. (1999).3 RESULT
Muelleria pseudogibbula Q. Liu & Q.X. Wang sp. nov.
Valves are lanceolate to linear-lanceolate with rounded apices. Valve length 20.5–25.0 μm, breadth 6.0–6.5 μm. The raphe is almost straight with two longitudinal canals alongside the axial area running parallel to each side of the raphe. Proximal raphe ends are deflected to the same directions and finish before the first row of areolae. Axial area is narrow and linear. Central area is small and elliptical. Striae are radiate near the center, becoming parallel near the apices. Central striae are more widely spaced, 19–21 in 10 μm, increasing to 25–26 in 10 μm distally.
In SEM, striae are composed of individual, circular, small areolae that are variable in size and becoming abruptly and distinctly expanded on each side of distal raphe (Fig. 2a, b). The raphe is straight, barely undulate and filiform (Fig. 2a). External distal raphe ends form two divergent branches in a "Y" shape (Fig. 2a, b). Proximal raphe ends are deflected to the same side of the valve and finish before the first row of areolae (Fig. 2a, c). Distal raphe ends curve slightly in the same direction as the proximal raphe ends, clearly bifurcating, finish onto the valve face/mantle junction (Fig. 2a, c). The axial area is narrow and linear, enlarging slightly in the middle of the valve to form an elliptical central area, and at the apices (Fig. 2a, b).
Type: CHINA. Zoigê Wetland, Sichuan province (SHTU, holotype SC20120505401, holotype illustrated in Fig. 1b, isotype SC20120505402).
Etymology: The specific epithet of the new species refers to its resemblance to M. gibbula.
Type locality: Zoigê Wetland, Sichuan province, China; altitude 3594 m, epiphytic on aquatic vascular plants, water pH 8.2.4 DISCUSSION
The new species is similar to Muelleria gibbula, M. regigeorgiensis and M. linearis. In its valve outline, Muelleria pseudogibbula is similar to M. gibbula, which has a linear to elliptical valve outline with broadly rounded apices (Spaulding and Stoermer, 1997; Spaulding et al., 1999). However, M. pseudogibbula has expanded areolae on each side of the distal raphe ends, these appear as lacking in M. gibbula and M. linearis M. pseudogibbula has rounded areolaeand M. regigeorgiensis Van de Vijver & Spaulding has C-shaped to reniform areolae (van de Vijver et al., 2010).5 ACKNOWLEDGEMENT
We are grateful to the collector of PANG Wanting, NI Yichen and FANG Yong for their help with collection samples in the field.
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