Campylodiscus sinensis B. Wu, Q. Liu et Q.X. Wang, 2013

Wu, Bo, Liu, Qi, Wang, Quanxi & Kociolek, J. Patrick, 2013, A new species of the diatom genus Campylodiscus (Bacillariophyta, Surirellaceae) from Dongtan, Chongming Island, China, Phytotaxa 115 (2), pp. 49-54 : 50-53

publication ID	https://doi.org/ 10.11646/phytotaxa.115.2.3
persistent identifier	https://treatment.plazi.org/id/5F7287F7-320A-C512-FF5F-F8C2FC85F442
treatment provided by	Felipe
scientific name	Campylodiscus sinensis B. Wu, Q. Liu et Q.X. Wang
status	sp. nov.

Treatment

Campylodiscus sinensis B. Wu, Q. Liu et Q.X. Wang , sp. nov. ( Figs. 2–3 View FIGURE 2 View FIGURE 3 ).

Cells solitary, with saddle-shaped valves, circular to subcircular in outline in valve view. Valves small, 22–28 µm in diameter (n=42). Costae evident, 3–5/ 10 µm. Central area distinctly circular to subcircular; width nearly half the diameter of the valve ( Figs. 2b, d View FIGURE 2 ). Central area delimited by a heavily silicified band, appearing hyaline in LM and often bisected by a wide (5–8 µm) silicified area. In the SEM, cells appearing suborbicular in outline when lying in valve view, with costae supporting the valve face by connecting the silicified band of the central part with the skirt and the mantle converging toward the center of the valve ( Figs. 3a, b View FIGURE 3 ). Internally, the valve is smooth, a silicified

band delimiting the central area is evident and bisected by wide silicified area ( Fig. 3b View FIGURE 3 ). The wide hyaline area surrounds two kidney-shaped depressions ( Fig. 3b View FIGURE 3 ), each with transapically-directed striae composed of single rows of areolae, 24–27 rows/ 10 µm ( Figs. 3b, i View FIGURE 3 ). Costae contain striae with double rows of areolae, 26–30 rows / 10 µm. Externally, the entire central area has many pyramid-shaped verrucae ( Figs. 3a, e, f View FIGURE 3 ). Two kidney-shaped convexities are present in the central area ( Figs. 3a, c View FIGURE 3 ). Costae contain striae formed by single rows of parallel areolae ( Figs. 3e, h View FIGURE 3 ). Parallel striae continue onto mantle ( Fig. 3d View FIGURE 3 ). The raphe is submarginal ( Fig. 3c View FIGURE 3 ), raised on a keel ( Figs. 3c, d, g View FIGURE 3 ) and interrupted at the valve margin ( Figs. 3c, g View FIGURE 3 ). There are two types of fibulae on the keel, one is fine, small, cylindrical, and do not extend inward onto the internal valve face ( Fig. 3h View FIGURE 3 , arrow). The other is robust, broadly cylindrical and extending out onto the internal valve face ( Fig. 3h View FIGURE 3 , arrowhead).

Type: — CHINA. Dongtan, Chongming Island, Shanghai, 31° 36.261’ N, 121° 52.344’ E. Epiphytic in puddle in the reed marshes, 9 of October 2008, s.n. (Holotype SNU!, slide D0056, Fig. 2B View FIGURE 2 ) GoogleMaps .

Comparison with similar taxa: —While there are many species of Campylodiscus , very few of them are small-sized. Campylodiscus clypeus, as the type of the genus, has large valves, 80–200 µm in diameter ( Poulíčková 2007), while in C. sinensis valves are small, 22–28 µm in diameter (n=42). We compare in Table 1 other species of genus Campylodiscus . Based on the features of these additional species (as reported in the literature), C. sinensis is distinguished from C. humilis Greville (1865: 233) , C. limbatus var. minutus Cleve (1883: 513) , C. minutus Grunow (1862: 438) and C. parvulus W. Smith (1851: 7) in the number of costae in 10µm. The striae are formed by a single row of puncta, which is different as compared to C. exiguus Grunow (1862: 441) , which has striae formed by double rows of puncta ( Rabenhorst 1864, De Toni 1890). These species have all been reported from coastal waters of Europe. With respect to small species found along the coasts of Asia, C. panduriger A. Schmidt (1875: 14) is a small-sized species described from the coast of Japan at Yokohama ( Schmidt 1875). Two other small forms, identified as Surirella scalaris Giffen (1967: 286) and “ C. spec.” are presented in Witkowski et al. (2000, plate 215, Figs. 4–6, and plate 216, Figs. 6, 7, respectively), both from the Indian Ocean off of Kenya. The feature of the two kidney-shaped protrusions found in C. sinensis appears to be unique to this species, and distinguish it from these other small species.

This is a unique species of Campylodiscus , by virtue of the two protuberances present near the center of the valve. Species in the genus with similar features are unknown to us. While not common, this species was readily visible in the material from Dongtan, and underscores the tremendous amount of work to be done to document the estuarine, benthic diatom flora of China.