Odontidium longiovalum Jüttner, D.M.Williams & E.J.Cox, 2017

Jüttner, I., Williams, D. M., Gurung, S., Vijver, B. Van De, Levkov, Z., Sharma, C. M., Sharma, S. & Cox, E. J., 2017, The genus Odontidium (Bacillariophyta) in the Himalaya-a preliminary account of some taxa and their distribution, Phytotaxa 332 (1), pp. 1-21 : 9

Odontidium longiovalum Jüttner, D.M.Williams & E.J.Cox , sp. nov. ( Figs 40–62 )

LM ( Figs 40–54 ): Frustules rectangular in girdle view ( Fig. 40 ). Valves linear, linear-elliptic to elliptic with valve margins tapering from valve centre in medium sized and smaller valves. Margins almost parallel in larger valves near valve centre, tapering near apices. Apices broadly rounded or weakly cuneate, in larger cells slightly protracted ( Figs 41 – 54 ). Valve dimensions (n=29): length 10.5 – 61.0 μm, width 6.0 – 10.0 μm. Transapical ribs primary, secondary ribs rarely present, positioned at an angle or perpendicular to sternum, 3 – 5 in 10 μm. Striae between ribs at an angle or perpendicular to sternum, 2 – 7 rows between primary ribs. Cingulum composed of many bands. SEM ( Figs 55–62 ): external valve surface slightly rippled ( Figs 59, 60 ). Larger and smaller spines present along valve margin and mantle in 1 – 2 rows. A single row of spines continuing around apices ( Figs 55, 57 – 59, 61, 62 ). Number of spines variable. Some valves possess only a small number of spines. Spines positioned on virgae. Virgae of variable width, vimines much shorter. Striae uniseriate, parallel, slightly radiate towards poles ( Figs 55, 57, 58 ). Sternum ill-defined, wide, narrowing close to apical pore field. In larger valves, sternum extending into apical pore fields ( Figs 57, 58 ). One rimoportula per valve present, close to apical pore field, replacing 3 – 5 vimines within a stria. External rimoportula opens as a simple slit. Internally, rimoportula with two protruding lips ( Figs 55 – 57 ). Apical pore field at each apex composed of round porelli surrounded by a rim ( Figs 57, 58 ). Internally ribs perpendicular or at an angle to valve margin ( Fig. 56 ). Valvocopula with a row composed mostly of 2 poroids on the pars exterior. Four copulae with a row composed of 1 or 2 poroids on the pars exterior and a single row of elongated poroids located on the pars interior ( Figs 61, 62 ).

Type: — NEPAL, spring in the upper Langtang Valley between Kyanjin Gompa and Kyangjin Kharka, Ingrid Jüttner, 26.11.2000. The holotype is slide no. NMW.C.2007.009.2000.La.spr.3/2, National Museum Wales, Cardiff, UK!

Etymology: —The name refers to the oval shape of the smaller valves.

Ecology and distribution:— Odontidium longiovalum was found in an alpine spring and stream in the Helambu and Langtang area of central Nepal and in an alpine stream in eastern Nepal. The spring in the Langtang Valley was fast flowing and located at the foot of a south facing slope with boulders and alpine grassland. Periphyton and bryophytes were abundant in the spring and its substratum was dominated by cobbles (NMW.C.2007.009.2000.La.spr.3/2). The stream in the Helambu area, situated at 4381 m a.s.l., was 3.5 m wide, fast flowing and its substratum consisted of boulders, cobbles and pebbles (NMW.C.2007.006.He07). The stream in eastern Nepal was a tributary to the Ghunsa Khola, a small alpine stream situated at 3575 m a.s.l., ca. 2.2 m wide with a cobble, pebble and gravel substratum (NMW.C.2007.006.K58). Conductivity at these sites varied between 21 and 74 μS/cm ( Table 2).

Figures

FIGURES 40–54. Odontidium longiovalum. LM. Fig. 40. Frustule in girdle view. Figs 41–54. Valve views. Figs 40, 41, 45, 46, 48, 53, 54. NMW.C.2007.006.K58: tributary to the Ghunsa Khola near the village of Hombu, Taplejung district, Nepal. Figs 42, 47, 50, 51. NMW. C.2007.009.2000.La.spr.3/2: spring in the Langtang Valley, Rasuwa district, Nepal. Figs 43, 44, 49, 52. NMW.C.2007.006.He07: stream south of the Laurebina Pass, Helambu, Nepal. Scale bar = 10 μm.

FIGURES 55–58. Odontidium longiovalum. SEM. Fig. 55. Frustule in valve view. Fig. 56. Internal view of valve. Fig. 57. Apical pore field and rimoportula. Fig. 58. Apical pore field. Figs 55–57. NMW.C.2007.009.2000.La.spr.3/2. Fig. 58. NMW.C.2007.006.K58. Scale bars = 3 μm (Fig. 55), 2 μm (Figs 56–58).

FIGURES 59–62. Odontidium longiovalum. SEM. Fig. 59. Detail of valve surface. Fig. 60. Areolae with occlusions. Fig. 61. Frustule in girdle view. Fig. 62. Mantle with rows of spines, and two girdle bands. Figs 59–60. NMW.C.2007.006.K58. Figs 61–62. NMW. C.2007.009.2000.La.spr.3/2. Scale bars = 2 μm (Figs 61–62), 1 μm (Fig. 59), 200 nm (Fig. 60).