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

Yu, Pan, You, Qingmin, Pang, Wanting & Wang, Quanxi, 2022, Two new freshwater species of the genus Achnanthidium (Bacillariophyta, Achnanthidiaceae) from Qingxi River, China, PhytoKeys 192, pp. 11-28 : 11

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

Figs 1A -AD , 2 -5

Description.

LM (Fig. 1A - AD ), valves are slightly irregularly linear-lanceolate in shape, with rounded or weakly protracted apices. Valve length 13-35.7 µm, breadth 3.5-4.5 µm (n = 200). Raphe valve is concave, with narrow, linear-lanceolate axial area, with a central area that is transapically rectangular or bow tie-shaped, usually slightly asymmetric. Striae radiate at the middle portion and nearly parallel towards apices, the number of striae is 18-20 in 10 µm at the middle portion, 26-32 in 10 µm near the apices. Rapheless valve is convex, axial area narrow linear-lanceolate and weakly expanded at the middle portion of the valve. Striae are nearly parallel, 16-26 in 10 µm in the centre and 22-30 in 10 µm near the apices.

In the SEM, both valves have a narrow hyaline area at the valve face and mantle junction (Figs 2A, B , 4A, B ). Raphe valve: Externally, the raphe is filiform and straight (Fig. 2A, B ), distal raphe ends are deflected to the same side (Fig. 2A-C, E ), and proximal raphe ends straight and teardrop-shaped (Fig. 2A, B, D, F ). Striae uniseriate, containing 3-6 round, oval or transapically-orientated areolae in the middle portion of the valve and 1-3 round, oval or transapically-orientated areolae at the apices (Fig. 2A-C, E ). Valve mantle with a single row of linear areolae extend along the valve, but with a slight interruption in the apices (Fig. 2B, C, E ). Internally, raphe terminates in raised helictoglossae close to the apices (Fig. 3A-D ), proximal raphe ends form small hooks and are distinctly deflected in opposite directions (Fig. 3A, B, E ). Areolae transapically elongated in the central portion of the valve, becoming larger and oblong at the apices (Fig. 3C-E ). Areolae are occluded by hymenes perforated by delicate slits and each hymene joins with the adjacent hymene (Fig. 3F ).

Rapheless valve: Externally, the axial area is linear, being weakly expanded in the central area (Fig. 4A, B ). Striae are uniseriate, comprise of 4-6 round or transapically elongated areolae in the central area (Fig. 4A, B, D ) and 1-4 round or irregular oblong areolae at the apices (Fig. 4A-C ). A row of slit-like areolae is present on the mantle (Fig. 4C, D ). Internally, axial area slightly raised, with a shallow cutting line at the middle portion (Fig. 5A, B, E ) and have a shallow depression at the ends of the axial area (Fig. 5A-D ). Areolae are transapically oval in the centre of the valve (Fig. 5A, B, E ) and large, irregular and oblong at the ends (Fig. 5A-D ). Areolae are occluded by hymenes perforated by delicate slits and each hymene joins with the adjacent hymene (Fig. 5F ).

Holotype

(designated here). SHTU! Slide QXH201801-Z7 in Lab of Algae and Environment, College of Life Sciences, Shanghai Normal University, Shanghai, China. Holotype illustrated in Fig. 1H, W .

Registration.

http://phycobank.org/103057

Type locality.

China. Qingxi River, Anhui Province, 30°14'39"N, 117°49'58"E, leg. Q.X. Wang and P. Yu, 23th January 2018.

Etymology.

The species is named for the place where it was found, namely Anhui Province.

Ecology.

Collected in one sample (QXH201801-Z7) on stone. Water temperature - 8.1 °C, pH - 7.8, Salinity - 0.05‰, TDS - 95.55 mg·l-1, EC - 99.3 μS ·cm-1, TN - 0.5 mg·l-1, TP - 0.03 mg·l-1, COD - 0.1 mg·l-1.

Distribution.

So far only known from the type locality.

Figures

Figures 1. A-AD LM valve views of Achnanthidium anhuense sp. nov. AE-AS LM valve views of Achnanthidium qingxiense sp. nov. Scale bar: 10 µm.

Figures 2. A-F Achnanthidium anhuense sp. nov., SEM external views of raphe valve A, B external view of an entire raphe valve C, E apices of the valve, showing the distal raphe ends D, F central area of the valve, showing the proximal raphe ends, D seems detail of A and F of B. Scale bars: 5 µm (A, B); 1 µm (C-F).

Figures 3. A-F Achnanthidium anhuense sp. nov., SEM internal views of raphe valve A, B internal view of an entire raphe valve C, D apices of the valve, showing the distal raphe ends E central area of the valve, showing the proximal raphe ends F internal areola openings with fine hymenate structures. Scale bars: 5 µm (A, B); 1 µm (E); 0.5 µm (C, D); 0.3 µm (F).

Figures 4. A-D Achnanthidium anhuense sp. nov., SEM external views of rapheless valve A, B external view of an entire rapheless valve C apices of the valve D central area of the valve. Scale bars: 5 µm (A, B); 1 µm (C, D).

Figures 5. A-F Achnanthidium anhuense sp. nov., SEM internal views of rapheless valve A, B internal view of an entire rapheless valve C, D apices of the valve E central area of the valve F internal areola openings with fine hymenate structures. Scale bars: 5 µm (A, B); 1 µm (E); 0.5 µm (C, D, F).