Delicatophycus liuweii, Liu & Li & Wu & Kociolek, 2021

Liu, Wei, Li, Yan-Ling, Wu, Han & Kociolek, John Patrick, 2021, Delicatophycus liuweii sp. nov., a new cymbelloid diatom (Bacillariophyceae) from an upper tributary of the Liujiang River, Guangxi, China, Phytotaxa 505 (1), pp. 63-70 : 64-66

Delicatophycus liuweii Y.- L. Li sp. nov. Figs 1–25

Description:— LM: Valves strongly asymmetrical to the apical axis, lanceolate, dorsal margin strongly arched, ventral margin nearly straight to slightly concave, except at mid-valve, where it is slightly tumid ( Figs 1–7 ). Ends obtusely rounded. Length 32–56 μm, breadth 8.0–9.5 μm. Maximum length/width ratio 6.0 (n=60). The axial area is moderately wide, linear-lanceolate in shape. Central area absent. Raphe strongly lateral, becoming filiform near the distal ends and slightly reverse-lateral near the proximal ends. Proximal raphe ends distinct, ventrally bent, external distal raphe ends dorsally deflected. Striae radiate. Stigmata 3–6 positioned on the ventral side of the central nodule and adjacent to the middle ventral stria. Striae in the middle 11–12 in 10 μm, becoming up to 20–21 in 10 um towards the ends, areolae 25–27 in 10 μm.

SEM: Externally, axial area moderately wide, curved, ventrally displaced near the central area ( Figs 14–19 ). Proximal raphe branches ventrally deflected ( Figs 18–19 ), distal raphe fissures strongly curved towards the dorsal side ( Figs 16–17 ). Striae radiate throughout ( Figs 14–15 ) and extending onto the mantle without interruption ( Fig. 18 ). Valve face areolae 25–27 in 10 μm. Stigmata 3–6, present on the ventral side near the central nodule ( Figs 18–19 ). Apical pore fields absent ( Figs 14–17 ).

Internally, the axial area is linear-lanceolate ( Figs 20–21 ). Distal raphe endings terminate as helictoglossae, deflected slightly off the main raphe axis ( Figs 22–23 ). The central nodule is indistinct. Raphe continuous, lacking an intermissio in the center ( Figs 20–21, 24–25 ). Stigmata 3–6, present on the ventral side near the central nodule ( Figs 24, 25 ). Each stigma is surrounded by siliceous protuberances ( Figs 24–25 ). Each stria is positioned within an alveolus internally ( Figs 20–21 ).

Type: — CHINA. Guangxi Province, Hechi City, Liujiang River, upper tributary of unknown name, 24° 44.56′ N, 107° 55.02′ E. 675 m asl, W.Liu on 8th July 2018. (holotype: Herbarium of Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences ! Slide # GXLJ01 = Fig. 1 ) .

Etymology: —The specific epithet ‘ liuweii ’ refers to the name of the sample collector.

Ecology: — Delicatophycus liuweii has so far only been found in the Liujiang River, in a littoral habitat with low CODMn (0.9 mg ·L- 1), BOD5 (4.05 mg ·L- 1) and NH 4 + -N (0.066 mg ·L- 1), and moderate DO (8.47 mg ·L- 1). Species associated in the collections containing D. liuweii include: Achnanthidium minutissimum (Kützing) Czarnecki (1994: 157) (16.1%), Rossithidium petersenii (Hustedt) Aboal in Aboal et al. (2003: 178) (5.7%), Lemnicola exigua (Grunow) Kulikovskiy, Witkowski & Plinski in Plinski & Witkowski (2011: 112) (4.5%), Humidophila contenta (Grunow) Lowe, Kociolek, J.R.Johansen, Van de Vijver, Lange-Bertalot & Kopalová (2014: 357) (5.4%), Halamphora montana (Krasske) Z. Levkov (2009: 207) (6.5%), Cocconeis placentula Ehrenberg (1838:194) (2.1%), Encyonopsis leei Krammer (2003: 514) (2.7%), Luticola mutica (Kützing) Mann in Round et al. (1990: 670) (2.1%), Nitzschia palea (Kützing) Smith (1856: 89) (14.8%), Nitzschia valdecostata Lange-Bertalot & Simonsen (1978: 58) (2.4%), Gomphonella olivacea (Hornemann) Rabenhorst (1853: 61) (2.8%), Navicula trivialis Lange-Bertalot (1980: 31) (6.3%) and other unidentified species of Gomphonema Ehrenberg (1832: 87) and Cymbella ( Agardh 1830: 1) .

Figures

FIGURES 1–13. Delicatophycus liuweii LM. Valve views showing size diminution series for the species. Fig. 1 is the holotype. Scale bar =10 μm.

FIGURES 14–19. Delicatophycus liuweii, SEM. External views. 14–15. External view of a whole valve. 16–17. Show the varied areolae at apices. 18–19. External view of valve center showing striae composed of areolae, 3–6 stigmata, and the proximal raphe endings. Scale bars =2 μm.

FIGURES 20–25. Delicatophycus liuweii SEM. Internal views. 20–21. internal view of a whole valve. 22–23. Showing valve apices. No differentiated porelli are apparent. 24–25. Internal view of valve center, 3–6 slit-like stigmata on the ventral side marked by irregular marginal tooth-like structures. Scale bars =2 μm.