Ulnaria ulnabiseriata D.M. Williams et Bing Liu, 2017

Liu, Bing, Williams, David M. & Tan, Lin, 2017, Three new species of Ulnaria (Bacillariophyta) from the Wuling Mountains Area, China, Phytotaxa 306 (4), pp. 241-258 : 248-251

Ulnaria ulnabiseriata D.M. Williams et Bing Liu , sp. nov. ( Figs 30–51 )

LM: Frustules rectangular in girdle view ( Fig. 36 ). Valves linear-lanceolate with protracted subcapitate to rostrate poles ( Figs 30–35 ). Valves with parallel sides at the centre, slightly tapering towards the poles from c. 1/3 down each half of the valve ( Figs 30–35 ). Transapical axis 6–8 μm, apical axis 105–229 μm (n = 50). Sternum central, distinctive, regular, extending length of valve. Striae broad, parallel, radiating only at poles, 9–11(often 10) in 10 μm. With respect to sternum, striae mostly opposite one another, few deviating, mostly, but not always, towards the poles ( Figs 30–35 , arrows). A single rimoportula at each pole, central area rectangular, c. 8×10 μm.

SEM: Frustules rectangular in girdle view, epivalve with valvocopula and three copulae ( Figs 37–40 , B 8–B5 ), as for hypovalve ( Figs 37–40 , B 1–B 4 ). Each band possessing a single row of poroids which bisects the pars interior and exterior, located at mid-line of each girdle band ( Figs 38–40 ). Valve face and mantle meet almost at right angles ( Figs 37–40 ). Valves with biseriate striae, situated opposite each other, equidistant until radiating at poles; striae extending to valve face-mantle junction then continued onto mantle ( Figs 37–40 , 42–46 ). Each stria formed from externally raised virgae with vimines, the latter having closing plates producing biseriate structure ( Figs 44–46 ). Each areola (including those on mantle) covered externally by velum ( Fig. 47 ). A single rimoportula present at each pole, each a pair of simple extended lips, situated close to sternum ( Figs 42–43 ). Two horn-like outgrowths located on top of each ocellulimbus ( Figs 38, 40 , 47 ). Mantle plaques present ( Figs 38–40 ). Internally, valves linear-lanceolate, with subcapitate to rostrate poles; striae biseriate almost opposite each other, near sternum becoming uniseriate ( Figs 49–51 ). Rimoportulae prominent, possessing the characteristic bilabiate shape, lying close to the sternum ( Figs 49, 51 ).

Type: — CHINA. Hunan: Zhangjiajie National Forestry Park, the course of Jinbian stream, at Shuirao Simen , 29°20’36” N, 110°28’13” E, 467 m a.s.l., Bing Liu , 29 th December 2015, (holotype BM! 101839, illustrated in Fig. 30 ; isotype JIU! G201605 , illustrated in Fig. 35 , both holotype and isotype indicated on the slide) .

Etymology: —The epithet ulnabiseriata is a combination of ulna and the term ‘biseriate’ to reflect its similarity to U. ulna and its biseriate striae.

Ecology:— The following environmental parameters were measured in the field. Electric conductivity was 102.7 ± 0.8 μS/cm, pH was 8.5 ± 0.7, and water temperature was 8.7 ± 0.2 °C. Since the diatom sample was scraped off the surfaces of stones and the water electric conductivity is near 100 μS/cm, Ulnaria ulnabiseriata can be considered an epilithic diatom characteristic of moderate electrolyte content freshwaters.

Figures

FIGURE 1. Map of the study sites: FR = Fanjing Mountain National Nature Reserve, GR = Gaowangjie National Nature Reserve, ZP = Zhangjiajie National Forestry Park.

FIGURES 30–36. Ulnaria ulnabiseriata sp. nov., LM. 30–35. Six valves showing variety of the valve, note some striae without opposite ones (arrows). 30. Photograph of holotype. 35. Photograph of isotype. 36. A frustule in girdle view. Scale bar =10 μm for all figures.

FIGURES 37–40. Ulnaria ulnabiseriata sp. nov., girdle view, SEM. 37. One complete frustule. 38–40. Details of the previous whole frustule, note the cingulum elements, especially the six closed girdle bands (labeled B1–B6). Scale bar =10 μm (Fig. 37), 5μm (Figs 38–40).

FIGURES 41–46. Ulnaria ulnabiseriata sp. nov., external view, SEM. 41. One whole valve. 42–43. Details of the previous two poles, note the alternate striae. 44–46. Details of the middle parts of the previous whole valve, note the opposite striae and biseriate striae becoming uniseriate striae at the end of each stria. Scale bar =10 μm (Fig. 41), 5μm (Figs 42–46).

FIGURES 47–51. Ulnaria ulnabiseriata sp. nov., SEM. 47. One pole in girdle view showing the ocellulimbus and the pore closing plates. 48. A whole valve. 49–51. Details of the previous whole valve. Scale bar =1 μm (Fig. 47), 10 μm (Fig. 48), 5 μm (Figs 49–51).

FIGURES 3–10. Ulnaria sinensis sp. nov., LM. 3. Whole frustule attached to single valve, in girdle view. 4. Holotype specimen. 5. Isotype specimen. 6–7. Two different valves. 8–10. Details of Fig. 4, note misaligned striae (arrows). Scale bars = 50 μm (Figs 3–7), 20 μm (Figs 8–10).