Delicata chongqingensis Wei Zhang, S.Q.Yang & S. Blanco, 2019

Yang, Song-Qi, Zhang, Wei, Blanco, Saùl, Jüttner, Ingrid & Wu, Zhong-Xing, 2019, Delicata chongqingensis sp. nov., a new cymbelloid diatom species (Bacillariophyceae) from Daning River, Chongqing, China, Phytotaxa 393 (1), pp. 57-66 : 59

Delicata chongqingensis Wei Zhang, S.Q.Yang & S. Blanco sp. nov. ( Figs 2–25 )

LM: Valves moderately dorsiventral, semi-lanceolate, dorsal margin evenly and moderately arched, ventral margin straight in the central section. Slightly protracted, rounded valve ends ( Figs 2–11 ). Length of the observed specimens 21.0–30.5 μm, width 6.0–8.3 μm, length/width ratio 2.9–4.0, median 3.5 (n=32). Axial area narrow, curved, not or slightly ventrally displaced. Dorsally central area forming a large, irregular semifascia, bordered on the dorsal side by 2–4 shortened central striae of different length. Raphe not or slightly ventrally displaced, distinctly lateral, becoming filiform near the distal ends and reverse-lateral near the proximal ends. On the ventral side in the valve centre striae slightly radiate or more or less parallel, sometimes slightly wider spaced, slightly radiate away from the centre and often becoming more or less parallel close to the apices. On the dorsal side shortened striae wider spaced, more or less parallel or slightly radiate. Away from the centre striae slightly radiate throughout the valve. Areolae not discernable in LM. Striae 11–15 in 10 μm, mostly 11–13 in 10 μm dorsally, 13–15 in 10 μm ventrally, slightly denser towards the ends (16–18 in 10 μm).

SEM: Proximal raphe branches curved to the ventral side terminating in small central pores that are slightly ventrally deflected ( Figs 12–17 ). Distal raphe fissures hooked towards the dorsal side ( Figs 12, 13, 18, 19 ). Striae composed of tilde-shaped or sigmoid areolae ( Figs 12–19 ) extending around the apices and onto the mantle. Three to four rounded or slit-like, isolated areolae are present on the ventral side near the central nodule ( Figs 14–17 ). Narrow linear axial area widening towards the semifascia in the valve centre. Raphe continuous internally, distally raphe ends terminating in small, knob-like helictoglossae which are offset and bent very slightly towards the dorsal margin ( Figs 20–22 ). Ventrally, one or two slit-like internal openings, marked by small marginal nodules, at the end of the central striae adjacent to the central area ( Figs 23, 24 ). Striae constitute alveoli internally, with oval or tilde-shaped internal areola openings ( Figs 21–25 ).

Type: — CHINA. Chongqing municipality, Daning River, 31° 39′ 42′′ N, 109° 27′ 50′′ E, elevation 680 m a.s.l., coll. Z.X. Wu, 20 April 2013 (holotype: slide DNR-1, illustrated in Fig. 8 ).

Etymology: —The specific epithet “ chongqingensis ” refers to the place from which the species is described.

Figures

FIGURES 2–11. Delicata chongqingensis, LM (DIC). Valve views, showing the valve variability of the holotype population, scale bar = 10 μm.

FIGURES 12–19. Delicata chongqingensis, SEM, external views. 12, 13. External view of the whole valve. 14–17. External view of the central part of the valve showing the dorsal semifascia, three to four isolated, rounded or slite-like areolae (arrows), and the shortened striae in the valve centre on the dorsal side. 18, 19. Valve apices and tilde-shaped areolae forming distinct undulate striae. Scale bars = 5 μm (Figs 12, 13), 4 μm (Figs 14, 15), 2 μm (Figs 16–18) and 3 μm (Fig. 19).

FIGURES 20–25. Delicata chongqingensis, SEM, internal views. 20. Internal view of a whole valve and the dorsal semifascia. 21, 22. Internal view of valve ends with helictoglossae. Figs 23, 24. Internal view of valve centre, central area bordered by shortened striae, and one or two slit-like areolae on the ventral side marked by small marginal nodules (arrowheads). Fig. 25. Internal view of an eroded part of the valve, showing the stria alveoli and the oval and tilde-shaped internal openings of the areolae. Scale bars = 5 μm (Fig. 20), 2 μm (Figs 21, 22, 25), 3 μm (Figs 23, 24).