Gomphonema baishaensis Y.-L. Li, 2025

Huang, Ji-Min, Guo, Ji-Shu, Ni, Hong-Ping, Xiao, Qiao-Zhi, Kociolek, John Patrick & Li, Yan-Ling, 2025, Gomphonema baishaensis sp. nov. (Bacillariophyta, Gomphonemataceae), a new diatom species from Guangdong Province, China, Phytotaxa 700 (3), pp. 257-268 : 259-263

Gomphonema baishaensis Y.-L. Li sp. nov. ( Figs 2–29 )

Description. LM. ( Figs 2–20 ): Valve clavate, broadest towards the headpole, with a rounded headpole and narrowly rounded footpole. Some individuals show a slight and inconspicuous constriction at the headpole apex. Valve length 12.5–32.0 µm, valve width 5.0–6.5 µm, valve length/width ratio varying between 2.4–5.1, median 3.8 (n = 30). The widest part of the valve is closer to the apex than to the central area, in small individuals near the central region. Axial area narrow, slightly wider in the central. Raphe slightly eccentric, slightly undulate. The central area is irregular, expanded due to one shortened striae on both sides. An isolated stigma is located to one side of the valve center. Striae slightly radiate throughout out the valve. The striae density is 8–10 within 10 µm in the center and 9–12 within 10 µm in the poles. Areolae not visible.

SEM. Valve exterior ( Figs 21–25 ): The raphe is slightly undulate ( Fig. 21 ). Proximal raphe ends dilated, drop - like in shape, slight deflection towards the stigma ( Figs 21, 23 ). External distal raphe ends hooked near the apices ( Fig. 22 ). Striae slightly radiate. On the valve most of the striae consist of a single row of slit-like areolae ( Fig. 21 ), with some of the striae near the mantle consisting of a double row of slit-like or short slit-like areolae, slit-like areolae that also form double rows in some striae near the apices ( Fig. 22 , arrow a), which become arranged in a single row and rounded on the mantle ( Fig. 25 , arrows b, c, d), 40–60 in 10 µm. A round stigma opening is present in the central area ( Figs 21, 23 ). At the footpole, the distal raphe end bisects apical pore field ( Figs 21, 24 ). The apical pore fields are spatially separated and morphologically distinct from the striae. The porelli of the pore fields are located on the valve face and mantle, with each pore being round in shape ( Fig. 24 ).

SEM. Valve interior ( Figs 26–29 ): Striae mostly consist of a single row of slit-like shaped areolae, some of which consist of double rows of round areolae. The raphe is straight, slightly undulate. The proximal raphe ends deflect to the same side as the stigma, curving into a hook shape ( Figs.26, 28 ). The stigma presents a slit-like opening. ( Fig. 28 ). Internal distal raphe endings terminate as small helictoglossae ( Figs 26, 29 ).

Diagnosis: Gomphonema baishaensis differs from G. tamilensis Karthick & Kociolek ( Karthick et al. 2012: 190) by striae density ( G. baishaensis , has 8–12 striae in 10 µm, which is higher than the 7–8 in 10 µm in G. tamilensis ), size range ( G. baishaensis measuring 12.5–32 µm in length and 5.0–6.5 µm in width, whereas G. tamilensis measures 26.6–27.5 µm in length and 6.6–7.4 µm in width). In terms of valve morphology, G. baishaensis has a rounded headpole, contrasting with G. tamilensis 's broader circular form. Both species attain maximum width in their upper valve regions, but the widest point in G. tamilensis lies nearer the central area, whereas in G. baishaensis it is closer to the headpole, this is more distinct in larger individuals. This feature is more evident in larger specimens, while in smaller individuals the widest part is closer to the central area.

Holotype (designated here):— BS 202172601 in Coll. Yan-Ling Li , Yunnan University, Kunming, China. Fig. 2 represents the holotype . Isotype YUNGL 20220329, Harbin Normal University, Harbin, China

Type locality: — CHINA. Guangdong Province: Baisha River, freshwater, 24°38′11′′ N, 113°30′26′′ E, elevation 45 m a.s.l., 26 th July 2021, scraping of rocks collected by Hong-Qu Tang.

Etymology:— baishaensis , refers to the type locality from which the new species was obtained.

Ecology:— Gomphonema baishaensis was found in a moderately alkaline river (pH = 8.1), 32.2 °C of water temperature, 225 µS/cm of conductivity and 7.91 mg /L of dissolved oxygen (DO). The dominant diatoms species observed in this area include Achnanthidium minutissimum (Kützing) Czarnecki (1994: 157) (2.3%), Aulacoseira granulata (Ehrenberg) Simonsen (1979: 58) (4.1%), Adlafia minuscula var. muralis (Grunow) Lange-Bertalot (1999: 32) (1.9%), Bacillaria paxillifera (O.F. Müller) T. Marsson (1901: 254) (0.2%), Craticula subminuscula (Manguin) C.E. Wetzel & Ector (2015: 229) (33.0%), Cymbella turgidula Grunow (1875) (0.5%), Fragilaria tenera (W. Smith) Lange-Bertalot (1980: 746) (4.2%), Gomphoneis clevei (Fricke) Gil (1989: 267) (3.7), Gomphonema minutiforme Lange-Bertalot & E.Reichardt (1993: 61) (10.2%), Navicula cryptotenella Lange-Bertalot (1985: 62) (3.0%), Nitzschia amphibia Grunow (1862: 574) (9.5%), N. clausii Hantzsch (1860: 40) (0.9%), N. palea (Kützing) W. Smith (1856: 89) (1.9%), N. fonticola (Grunow) Grunow (1881) (1.4%), N. paleacea (Grunow) Grunow (1881) (10.7%), Planothidium joursacense (Héribaud) Lange-Bertalot (1999: 277) (1.9%), Psammothidium subatomoides (Hustedt) Bukhtiyarova & Round (1996: 13) (1.9%), Seminavis strigosa (Hustedt) Danieledis & Economou-Amilli (2003: 30) (0.5%), and Tabularia fasciculata (C. Agardh) D.M. Williams & Round (1986: 326) (2.8%).

Figures

FIGURES 2–20. Light microscopy of Gomphonema baishaensis sp. nov. from the holotype population, valve views showing the size diminution series. Fig. 2 represents the holotype. Scale bar = 10 µm.

FIGURES 21–25. Gomphonema baishaensis sp. nov. SEM, external views. Fig. 21. Exterior view of whole valve showing slit-like areolae, axial area and proximal and distal raphe ends. Fig. 22. External view of the headpole with distal raphe end curved on the mantle, slit-like areolae form double rows in some striae near the apices (arrow a). Fig. 23. Exterior of valve centre showing proximal raphe ends and rounded stigma opening. Fig. 24. External view of the footpole with the external distal raphe end curving onto the valve mantle and apical pore field porelli spatially separated from areolae and morphologically distinct from the areolae. Fig. 25. The girdle view (Arrows b, c, and d, point out changes in areola arrangement). Scale bar = 3 μm (Fig. 21), 1 μm (Figs 22–24), 2 μm (Fig. 25).

FIGURES 26–29. Gomphonema baishaensis sp.nov. SEM, internal views.Fig.26. Internal view of whole valve showing the raphe, central area and helictoglossa at poles. Fig. 27. Internal view of headpole showing the helictoglossae. Fig. 28. Interior view showing the central nodule with recurved proximal raphe ends and slit-like stigma opening. Fig. 29. Internal view of footpole showing the helictoglossae and pseudosepta. Scale bar = 2 µm (Figs 26, 28–29), Scale bar = 1 µm (Fig 27).