Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae Author Long, Ji-Yan 0000-0001-8160-089X College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China & 2215656702 @ qq. com; https: // orcid. org / 0000 - 0001 - 8160 - 089 X 2215656702@qq.com Author Liu, Bing 0000-0002-8516-325X College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China & jsulb @ outlook. com; https: // orcid. org / 0000 - 0002 - 8516 - 325 X jsulb@outlook.com Author Rioual, Patrick 0000-0001-9491-9197 Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, P. O. box 9825, Beijing 100029, China & CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China & prioual @ mail. iggcas. ac. cn; https: // orcid. org / 0000 - 0001 - 9491 - 9197 prioual@mail.iggcas.ac.cn Author Yang, Bin 0000-0002-1123-9477 College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China & 2927378586 @ qq. com; https: // orcid. org / 0000 - 0002 - 1123 - 9477 2927378586@qq.com Author Zhou, Min 0009-0009-2832-5417 College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China & 2509776606 @ qq. com; https: // orcid. org / 0009 - 0009 - 2832 - 5417 2509776606@qq.com text Phytotaxa 2023 2023-04-18 592 2 163 177 http://dx.doi.org/10.1094/PDIS-04-22-0755-PDN journal article 10.11646/phytotaxa.592.2.11 1179-3163 7840352 Surirella liubingii J.Y.Long sp. nov. (LM: Figs 1–14 , SEM: Figs 15–26 , 102, 103 ) Observations:— LM: Valve outline long-ovate to ovate with broadly rounded headpole and cuneate footpole ( Figs 1– 14 ). Valve dimensions (n = 21): length 22–33 μm, width 8.5–9.9 μm (measured at widest part of the valve), length/width ratio 2.3–3.7. Costa-stria bundles (CSBs) distinct, alternated with over-fibula costae (OFCs) from pole to pole. CSBs not reaching valve margins because the internal wall of raphe canal growing into cell cavity to form a “pseudoseptum” from the valve margin (indicated by two arrows in Fig. 4 , see also Figs 21–23 ). CSBs parallel at the valve middle, slightly radiate approaching apices. Fibulae distinct, extending to midline, 6–7 in 10 μm. SEM: Each CSB mostly composed of three costae and four striae, but occasionally two costae and three striae or four costae and five striae ( Figs 15–17 ). Tiny rib-like thickenings produced externally ( Fig. 18 , arrows). Striae multiseriate, composed of 3 or 4 rows of areolae, 24–26 in 10 μm (measured from SEM images, n = 3). Outside openings of areolae round to slit-like ( Figs 18–20 ). Raphe canal located directly on mantle. Distal raphe endings simple and interrupting at both apices ( Figs 19, 20 , two arrows respectively). Internally, wall of raphe canal growing into cell cavity to the extent that the internal raphe canal wall is developed to form a longitudinal siliceous plate (a “pseudoseptum” from the valve margin, indicated by two double-headed arrows in Fig. 21 ), which hides the portula structure. The wall of the raphe canal is striated ( Fig. 26 ). Fibulae robust, occasionally bifurcate, extending to valve midline ( Figs 21–23, 25 , 102 ). Raphe continuous at headpole ( Fig. 24 , arrow), but interrupted at footpole ( Fig. 26 , two arrows). One portula produced between two adjacent fibulae ( Fig. 103 , three arrows). FIGURES 43–48. Surirella minuta , SEM , external view. 43, 44. Two valves showing the valve shape and the pattern of costa-stria bundles (CSB, labeled with white arrows in Fig. 43) alternated with over-fibula costae (OFC, labelled with black arrows in Fig. 43) from pole to pole. 45, 46. Details of the middle section of the valve (Fig. 45 from Fig. 43, Fig. 46 from Fig. 44), note the pattern of CSB alternated with OFC and multiseriate striae. 47, 48. Details of the apices from Fig. 43. Note the raphe endings interrupted at both the headpole (Fig. 47) and footpole (Fig. 48). Scale bars = 5 μm (Figs 43, 44), 1 μm (Figs 45–48). Type:— CHINA , Qinghai province , Menyuan County : unnamed freshwater river course, sampling point 37°27'28" N , 101°23'15" E , 2940 m asl . Bing Liu , 18 th July 2019 ( holotype slide JIU ! DIA202315 , specimen circled on slide = Fig. 1 ) . Etymology:— Named after Dr. Bing Liu who is the first author’s supervisor and who collected the samples. Ecology and distribution:— Epilithic in river. The following environmental parameters were measured. Conductivity was 448 ± 1 μS̔cm –1 , pH was 8.36 ± 0.03 and water temperature was 11.9 ± 0.5 °C. So far, Surirella liubingii has only been found in the type locality.