Urosolenia curvata 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 : 32-34

Urosolenia curvata Karthick & Kociolek , sp. nov. ( Figs 5–6 ; holotype illustrated in Fig. 5–B )

Cellulae singulars vel binatim. Frustula sub-cyclindrica valvis asymmetrica conicis terminatibus extensa tubulari. Calyptra rotundata ad basim, late angusto base perforata ab areolam. Areolae dispositae plus minusve fasciculis. Extensio curva origine in latere uno valva flexa versus latis oppositum. Frustula omnia fracta, hinc longitudinem frustuli non suppetum. Lamina extensa visibilis in LM. Latitudo frustuli 4.5–6.8 µm. Longitudo processus 15.9–25.0 µm. Copulae 7–8/ 10 µm.

Cells isolated or joined in pairs. Frustules sub-cylindrical with asymmetric, conical valves that end with a tubular extension. Calyptra rounded at base, with mantle narrow and base perforated. Areolae organized more or less into fascicles. Curved tubular extension originates from one side of valve and bend towards opposite side. (All frustules observed were broken; hence total frustule length is not available). Extended lamina visible in LM. Frustule width 4.5–6.8 µm, length of process 15.9–25.0 µm, copulae density 7–8/ 10 µm.

Type: — Fresh-water Diatoms 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-5-1883, Centre for Ecological Science Herbarium Diatom Collection , Indian Institute of Science, Bangalore, INDIA; isotypes BM 101459) .

Etymology: —Named for the curved process of the valve terminus.

Observations: —In the SEM, the calyptra is rounded at the base ( Fig. 6–F ), with a narrow mantle ( Figs 6– A, D, E ). It has long, arched process. The base of the calyptra is perforated by areolae, which are organized more or less into indistinct fascicles. Narrow ribs extend onto and up and along the calyptra’s extension ( Figs 6–D, G ). Girdle bands are imbricated, composed of 9–11 rows of round to irregularly–shaped porelli ( Figs 6– B, C ). Marginal lamina extended into teeth ( Fig 6–D, E ). Areolae on copulae 9–10 in 1 µm and areolae on valve 6–7 in 1µm. Number of poroids ranges from 2–5 on the valve. The terminal end of the process is sharp pointed open with teeth ( Fig 6–G ).

Urosolenia curvata differs from U. diademata Rott & Kling by the shape and tip of the seta. The process of U. curvata is strongly curved when compared to other known Urosolenia ( Rott et al. 2006, Sala et al. 2008). Urosolenia diademata has a seta tip with sharp pointed teeth, sometimes with a central ligula and lateral teeth (Fig 9 in Rott et al. 2006) or extended into a long fine hair-like seta ( Fig 8 in Rott et al. 2006). The ribs along the base of the process in U. curvata are well developed when compared to those in U. diademata (Fig 30 in Rott et al. 2006). It is difficult to compare features of the copulae between U.curvata and U. diademata since it has not been illustrated for the latter species. Urosolenia curvata also differs from U. amazonica by shape and lack of ornamentation on the valvocopula.

Figures

FIGURE 5. Urosolenia curvata LM. Details of valves, process and girdle bands. Scale bar = 10 µm.

FIGURE 6. Urosolenia curvata SEM. A. External view showing the valve and the long valve extension. B. External view of the valve copula region without areolae. C. External and internal view of the areolae on the girdle band. D. External view of the valve showing the structure of the valve lamina and poroids on the base of the valve extension. E. External view of the valve extension base showing the ribs and poroids. F. Internal view of the valve showing the absence of rimoportula. G. External view of the valve extension shows the terminal end of the process are sharp pointed open with teeth. Scale bars: Fig. A: 10 µm; Fig. G: 2 µm; Figs. B, C, D, E, F: 1µm