Diploneis guangdongensis W.W.Wu, Y.H.Gao & C.P.Chen, 2022

Wu, Weiwei, Sun, Lin, Li, Xuesong, Liang, Junrong, Gao, Yahui & Chen, Changping, 2022, A new small marine Diploneis species (Diploneidaceae, Bacillariophyta) from Guangdong Province, China, Phytotaxa 560 (2), pp. 233-240 : 234-235

Diploneis guangdongensis W.W.Wu, Y.H.Gao & C.P.Chen spec. nov. (LM Figs 1–20 , SEM Figs 21–32 )

Description:— LM: The valves are elongated-elliptical with parallel margins and round apices ( Figs 1–20 ). The valve length is 6.5–12 µm, and the breadth is 3.0–4.0 µm. The axial area is narrow. The central area is distinct and quadratic to slightly rectangular in shape. Longitudinal canals are narrow and lanceolate in the flat median portion. The raphe is a narrow straight slit. Striae are not visible under LM.

SEM: The valve surface is almost flat. Along both sides of the axial area, the longitudinal canal is lanceolate and linear, open outside by one row of C-shaped poroids throughout the whole length of the valve ( Figs 22–24 ). The openings of the canal are covered with volate occlusions externally ( Figs 23, 26 ). At the valve apices, the longitudinal canal circles the distal raphe endings ( Figs 21–23 ). The axial area is very narrow and linear. The central area is quadratic to slightly rectangular, ca. 0.83–0.90 µm wide. Externally, the raphe is a narrow straight slit, with simple and slightly expanded drop-like proximal ends ( Figs 24–25 ). The distal raphe ends are simple and bent to the same side of the valve, terminating at some distance from the valve apices ( Figs 22–23 ). The area with volate occlusions occupies approximately one-fourth to one-sixth of the valve width ( Figs 21, 26 ). The alveoli open externally via elongated slits ( Fig. 22 , white arrow). The slits are the areola occlusions, short and narrow, rarely branched. The striae are parallel in the middle of the valve, becoming slightly radiated at the valve apices, 30–35 in 10 µm. The elongated slits are formed as an interspace between costae with the same shape ( Fig. 24 , white arrow). Each marginal flap is elongated to the margin of the valve. The other part of the alveolate striae is covered by a broadly semilune hyaline area at the middle of the valve, merging with the longitudinal canal ( Figs 21, 25 ).

Internally, the longitudinal canal is nonporous and enclosed by a thick silica plate ( Figs 27, 29–30 ). The internal longitudinal canal is less silicified, the raphe is not placed in a depression formed by the longitudinal canals. The proximal raphe ends are slightly expanded into small, drop-like central pores bent to the same side of the valve ( Figs 29, 32 ). The distal raphe ends are slightly expanded and straight ( Figs 30–31 ). Transapical costae are narrower than alveoli in both inner and outer valves ( Figs 24–25 , 27, 29 ). The intercostal spaces consist of elongated alveoli ( Figs 29–30 ), each occluded by a thin siliceous layer, bearing perforations in a hexagonal array ( Figs 29–30 ). The cingulum is composed of two copulae without ornamentation ( Figs 25 , 28 ).

Type: — CHINA. Guangdong Province, Shantou City , sandy beach, 23.4378°N, 117.1369°E, 10 May 2020, L.Y. Tan, (holotype slide ST-200510-1! = Fig. 2 ; isotype Slide ST-200510-2, both deposited in the Biology Department Herbarium, Xiamen University (AU), China.

Etymology: — The epithet “ guangdongensis ” refers to the site where the new taxon was collected.

Figures

FIGURES 1–20. Diploneis guangdongensis sp. nov. LM. 1–20. Valve view showing the size and shape. Fig. 2. Holotype specimen. Scale bars = 10 µm.

FIGURES 21–26. Diploneis guangdongensis sp. nov., SEM external valve view. 21. External view of the whole valve. 22–23. External view of the elongated slits (Fig. 22, white arrow) and distal raphe endings. 24. Expanded, drop-shaped proximal raphe endings and structure of the longitudinal canal; the elongated slits are formed as an interspace between costae (white arrow). 25. Girdle bands. 26. External opening of alveoli covered with volae. Scale bars = 1 µm (Figs 21–22, 24–26); 500 nm (Fig. 23).

FIGURES 27–32. Diploneis guangdongensis sp. nov., SEM internal valve views. 27. View of the entire valve. 28. Girdle bands. 29. Valve central area with slightly expanded proximal raphe endings bent to the same side of the valve. 30. Distal raphe endings and elongated alveoli occluded by a thin siliceous layer with perforations arranged in a hexagonal array. 31–32.Areolae in the corroded valve. Scale bars = 1 µm (Figs 27–28, 30, 32); 500 nm (Figs 29, 31).