Sellaphora constrictum J.P. Kociolek

You, Q-M., Kociolek, J. P., Cai, M-J., Lowe, R. L., Liu, Y. & Wang, Q-X., 2017, Morphology and ultrastructure of Sellaphora constrictum sp. nov. (Bacillariophyta), a new diatom from southern China, Phytotaxa 327 (3), pp. 261-268 : 262-263

Sellaphora constrictum J.P. Kociolek & Q-M You, sp. nov. ( Figs 1–17 ; Fig. 1 is of the holotype)

DESCRIPTION: Valves broadly linear, slightly constricted at the middle, margin appearing wavy or undulate, with rounded apices, length: 29.0–52.0 μm, width in the middle: 9.0–10.5 μm, greatest width: 9.5–11.0 μm. Raphe filiform to lateral and undulate. Axial area narrow and undulate with a small, sub-rounded or elliptical central area. Central striae relatively sparse and slightly radiate, 14–16/10 μm, striae more dense and radiate at the ends, 17–20/10 μm. Longitudinal ridges appear on either side of the axial area (see arrow in Fig. 5 , this feature is not apparent in all LM images). Areolae not resolved with LM.

The valve exterior has a slightly elevated narrow and undulate conopeum ( Fig. 10 : arrow A; Fig. 12 : arrow C), and is bordered on each side by a narrow trough ( Fig. 10 : arrow B). The trough is continuous and weakly expanded laterally through the central area ( Fig. 12 : arrow A) but not evident near the apex ( Fig. 13 ). The axial area is narrow, undulate, slightly elevated in the central and continues in the trough bordering the raphe branches. Towards the margin, there are three longitudinal ridges: one ridge borders the trough ( Fig. 10 : arrow C; Fig. 12 : arrow B); the other ridge is straight, near the valve margin ( Fig. 11 : arrow A) and the third ridge is almost along the border of the valve face and the mantle ( Fig. 11 : arrow B). The central area is slightly wider, forming an elliptical area ( Fig. 12 ). The raphe is undulate, with proximal raphe ends small, elliptical, and deflected slightly to one side and ending with small pores ( Fig. 12 ). Distal raphe ends are deflected to the same side and onto the mantle ( Fig. 13 ). Externally, there are two types (I and II) of areolae: type I areolae are present near the axial area and are small and rounded (48–54 / 10 μm). These areolae exist in narrow and deep grooves. The areolae are expanded in the central area and form the shape of a diamond or subdiamond that occupies up to 1/2 of the valve face ( Fig. 12 ). Type II areolae occur between type I areolae and the valve margins (40–46 / 10 μm). The type II areolae are with two longitudinal ridges on each side of the valve ( Fig. 11 : arrows A and B) .

Internally, the valves are relatively flat ( Fig. 14 ). The axial area is narrow and straight, slightly expanded in the central area. Raphe is straight, with proximal raphe ends not expanded, asymmetric, and deflected to the same side ( Fig. 15 ). Distal raphe ends terminate in elongated helictoglossae. There is a larger foramen-like pit at the end of valve that does not penetrate to the exterior ( Fig. 16 ). The striae have rounded areolae that are not differentiated internally. Areolae possess hymenate occlusions ( Figs 16–17 ).

Type:— CHINA. Guizhou Province: Maolan Nature Reserve, 25º15′42” N, 108º04′13” E, The new species was found in mixed samples of benthos, roots and scrapings from rocks from a tree-lined stream, collected by Q-X. Wang & J.P. Kociolek, 4 October 2015 (holotype: SHTU! slide and material GZ-1510089, Biology Department Diatom Herbarium, Shanghai Normal University, Shanghai, China, here illustrated as Fig. 1 ; isotype: COLO! material 10464, Kociolek Collection, University of Colorado, Museum of Natural History Diatom Herbarium , Boulder, USA).

Etymology:—The species is named for its outline, which is slightly constricted in the middle part of the valve.

Remarks:— Sellaphora constrictum sp. nov. was found in two regions that are located in the south of China, within similar habitats (clear, alkaline freshwater streams). The new species is rare in samples from Wuzhishan Mountain. In this study, the frustule in fig. 4 is from Wuzhishan Mountain, and all other frustules in the images are from Maolan Nature Reserve.

Figures

FIGURES 1–9. Sellaphora constrictum sp. nov., light microscopy.Valve view, size diminution series. Figure 1 is of the Holotype. Fig. 1– 3, 5–9 are from samples of Maolan Nature Reserve, Fig. 4 is from sample of Wuzhishan Mountain.Arrow in Fig. 5 shows the longitudinal ridge borders the trough. Scale bar =10 μm.

FIGURES 10–13. Sellaphora constrictum sp. nov. SEM, external views. Fig. 10. Valve view of entire valve, showing constriction in the middle of the margins, undulation of raphe, two types of areolae (arrow I and arrow II), conopeum (arrow A), the trough borders the conopeum (arrow B) and the ridge borders the trough (arrow C). Fig. 11. Valve view of entire valve, showing the ridge near the valve margin (arrow A) and the ridge along the border of the valve face and the mantle (arrow B), the mantle (arrow C) and the girdle (arrow D). Fig. 12. Central part of the valve, showing dilated proximal raphe ends, two types of areolae, the trough borders the conopeum (arrow A), the ridge borders the trough (arrow B) and expanded conopeum (arrow C). Fig. 13. Valve apex, showing distal raphe end curved on the mantle and arrangement of striae at apices. Scale bar =2 μm.

FIGURES 14–17. Sellaphora constrictum sp. nov. SEM, internal views. Fig. 14. Valve view of entire valve, showing straight raphe and arrangement of striae. Fig. 15. Central part of the valve, showing asymmetric proximal raphe ends deflected in the same direction and arrangement of striae. Note there is only a single type of areolae evident internally. Fig. 16. Valve apex, showing larger foramen-like (pit) that does not penetrate to the exterior. Fig. 17. Valve apex, showing the long helicotoglossa. Scale bar =2 μm.