Encyonema oblonga Qi Liu & Shulian Xie, 2021

Liu, Qi, Li, Jiajia, Wang, Quanxi, Kociolek, John Patrick & Xie, Shulian, 2021, Encyonema oblonga (Bacillariophyta, Cymbellaceae), a new species from Shanxi Province, China, Phytotaxa 480 (3), pp. 284-290 : 285

Encyonema oblonga Qi Liu & Shulian Xie sp. nov. ( Figs 1–18 ).

Description: Valves nearly symmetrical, linear-elliptical, dorsal and ventral margins almost parallel, ends broadly rounded. Length 21–30 μm, breadth 5.5–7.0 μm. Axial area narrow, linear. Central area asymmetric, formed by a distinctly-shortened stria on the ventral side and one- two slightly-shortened stria on dorsal side. Raphe filiform, proximal raphe ends are weakly expanded and deflected dorsally and distal raphe fissures are deflected ventrally. Striae parallel, becoming radiate at the ends, 10–11 in 10 μm. Areolae are distinct, 24–28 in 10μm.

In the SEM, externally, striae extend from the axial area to the mantle and are composed of individual lineate areolae ( Figs 11 , 14). Areolae bordering the axial area are smaller than the others ( Figs 11 , 14). Raphe filiform, proximal raphe ends are dilated and distal raphe end are hooked ( Figs 11, 13 , 14). Internally, raphe slits are straight, the intermissio is not present ( Fig 15, 17 ). Distal raphe ends terminate as helictoglossae ( Figs 15, 16 ). Striae are separated by well-developed intercostal ribs. The areolae are rectangular to elliptic. Beam stubs project above the intercostal ribs ( Ohtsuka et al. 2004) ( Figs 15–18 ). Stigmata and apical pore fields are absent.

Type:— CHINA. Shanxi Province, Manghe National Nature Reserve . N 35°17′20″, E 112°31′35″, altitude 826m, pH 8.6, temperature 15℃, Date: September 2017, Collector: Qi Liu & Jiajia Li. (slide 201709046-1 , holotype illustrated in Fig 2 ! Isotype JPK Collection, COLO, slides201709046-2 ) .

Etymology:—The species epithet refers to the oblong shape of the valve.

Ecology and distribution: Encyonema oblonga was found in Manghe rivers and Yuntai Mountains. pH 8.6, temperature 15℃and conductivity 625μS/cm in Manghe river, Shanxi province in September 2017. pH 8.5, temperature 19℃ and conductivity 475μS/cm of a small river at Yuntai Montains, Henan Province in May 2018. These rivers are a part of Yellow River basin.

Figures

FIGURES 1–10. Encyonema oblonga sp. nov. LM. Size diminution series of specimens from the holotype slide. Valve views. Scale bar = 10 µm. FIGURES 11–13. Encyonema oblonga, sp. nov. SEM. External views. Fig. 11. Whole valve, showing slit-like areolae without occlusions extending from valve face onto the mantle. Raphe is arched, with dilated proximal ends deflected dorsally, and distal ends hooking onto the ventral margin. Fig. 12. Apex, showing hooked nature of the distal raphe end. Fig. 13. Central area of the valve with dilated proximal raphe ends terminating close to one another.

FIGURES 14–18. Encyonema oblonga, sp. nov. SEM. Fig. 14. External view, with girdle bands evident. Slit-like areolae become much smaller on the mantle. Cingulum elements are of the open type. Figs 15–18, internal views. Fig. 15. Valve view showing continuous raphe through the center, lacking an intermissio. Helictoglossae terminate well before the valve end. Fig. 16. Apex of the valve showing striae with short stubs projecting within the striae. Fig. 17. Center of the valve, showing raphe lacks an intermissio. Fig. 18. Fractured valve showing raphe to be of the key and lock type.