Urosolenia extensa Karthick & Kociolek, 2011

Karthick, B. & Kociolek, J. P., 2011, Four new centric diatoms (Bacillariophyceae) from the Western Ghats, South India, Phytotaxa 22 (1), pp. 25-40 : 34-35

Urosolenia extensa Karthick & Kociolek , sp. nov. ( Figs 7–8 , holotype illustrated in Fig. 7–A )

Frustula cylindrica. Valvae symmertica conicae, angustatis longissimis, rectis ad undulates. Processus positatus ad centrum valvae, extense ramo-simili visibili LM. Latitudo frustuli 3.2–5.1 µm. Longitudo processes 15.4–44.4 µm. Copulae 5–7/ 10 µm.

Frustules cylindrical. Valves symmetrical, conical, continuing in a very long straight to slightly undulated process. Process positioned on valve center. Process possessing branch-like extension visible in LM. Frustules width 3.2–5.1 µm, length of process 15.4–44.4 µm, copulae density 5–7/ 10 µm.

Type: Hirebhaskar Dam (14°05’48” N, 74°53’30”E, altitude 552 meters above sea level), Sharavathi River , Shimoga District , Karnataka, India. Collected by H P Gandhi on 11 th January 1955. (Sample No. Sr. 110 in Gandhi's collection) (holotype CESH-5-1884, Centre for Ecological Science Herbarium Diatom Collection , Indian Institute of Science, Bangalore, INDIA; isotypes BM 101460) .

Etymology: Named for the elongated process of the valve.

In the SEM, the calyptra is funnel-shaped, tapered to form a tubular, extended process ( Figs 8–A, B). Striae of the calyptra are in linear rows ( Figs 8–A, G). The linearly arranged striae can be interrupted by elongated, narrowly rectangular openings ( Figs 8–B, E). The elongated girdle consists of imbricate broad half bands, each isolated by a rim-like structure. Regularly distributed elongated areolae are present on the girdle ( Fig 8– C, D). The base of the calyptra is a rim without additional ornamentation. The conical part of the valve has small areolae with density of 8–9/ 1 µm. The extension process possesses a small branch like projections and ends bluntly pointed ( Fig 8–F).

Urosolenia extensa differs from all other known Urosolenia species by its shape and absence of structure on valve lamina as observed in U. curvata and U. diademata Rott & Kling ( Rott et al. 2006). U. extensa can be differentiated from the U. delicatissima by the absence of buttonhole shaped external labiate opening on the valve ( Sala et al. 2008. Fig 13, 14) and the presence of branch like projections on the process ( Fig 8–F).

Figures

FIGURE 7. Urosolenia extensa LM. Details of valves, process and girdle bands. Scale bar = 10 µm.