Nitzschia taylorii Alakananda, P.B.Hamilton & Karthick, 2012

Alakananda, B., Mahesh, M. K., Hamilton, Paul B., Supriya, G., Karthick, B. & Ramachandra, T. V., 2012, Two new species of Nitzschia (Bacillariophyta) from shallow wetlands of Peninsular India, Phytotaxa 54 (1), pp. 13-25 : 15-19

Nitzschia taylorii Alakananda, P.B.Hamilton & Karthick , sp. nov. ( Figs 1–25 )

Valves lanceolate to linear lanceolate with protracted round to capitate apices. Valve mantle wider on keel side with siliceous nodules present immediately below keel. Length 22–42 µm, width 5–7.5 µm with 21–25 striae in 10 µm and 10–14 fibulae in 10 µm. Keel marginal, rounded, elevated from valve face and mantle ( Figs 13, 14 ). Raphe continuous from apex to apex without central area ( Fig. 18 ) and with terminal apices deflected towards valve face as a continuous loop across apex mantle ( Figs 15, 17 ). Striae uniseriate across valve face, extending onto keel ( Fig. 16 ). Mantle on opposite side of keel, with 2–3 elongated areolae and a broad hyaline basal margin ( Fig. 18 ). On keel side, mantle with 2–4 elongated areolae comprising each stria ( Figs 20, 21 ) with a solid surface at basal margin scattered with small papillae ( Fig. 26 ). Areolae on valve face round to elongated depressions, not occluded ( Fig. 22 ). Internally, each stria covered by hymen, and fibulae round to rectangular in shape throughout valve ( Figs 23, 25 ). Cingulum composed of numerous open copulae. Epicingulum of four bands, all with different surface structure. Valvocopula with single row of large elliptical pores on pars exterior and a row of small fine papillae along bottom of band ( Figs. 20, 26 ). Second and third bands with narrow external exposure, with no visible pores, but with fine papillae along bottom of band ( Fig. 26 ). Fourth band broad with a series of narrow elongated pores along pars exterior and a wide area devoid of structure at base of band ( Fig. 21 ).

Type:— INDIA. Bangalore : Begur wetland situated at Bangalore, 12° 52’ 20" N, 77° 37’ 58" E, elevation 900 m, March 2009. B. Alakananda & G. Supriya, s.n. (holotype CESH-5-1881! (circled specimen on slide); isotype CANA 85055 ! (circled specimen on slide)) .

Ecology:— Nitzschia taylorii was found in three wetlands viz., Begur, Hulimavu and Vaderahalli, characterized by basic pH (8.6 ± 0.6), alkalinity of 293.3 ± 80.8 mgL -1 and conductivity of 735.7 ± 322.5 µScm -1. Nitrate and phosphate values of these wetlands were 0.56 ± 0.95 mgL -1 and 0.33 ± 0.39 mgL -1 respectively. BOD and COD of these wetlands were recorded as 13.5 ± 7.9 mgL -1 and 37.3 ± 11.7 mgL -1 respectively.

Etymology:— The species epithet is named for our colleague and friend Dr. Jonathan Charles Taylor (North West University, South Africa) whose support for diatom studies in India is hereby acknowledged and who has been an inspiration to both Karthick and Alakananda.

Observations:— Nitzschia taylorii is distinguished by the separation of the keel from the valve face, the continuous raphe, large uniseriate areolae on the keel, row of nodules on the mantle below the keel, and the distinct morphology of the epicingulum bands. This taxon can be compared to N. solita Hustedt (1953: 152) in its general outline, although N. taylorii is more lanceolate (not constricted linear-lanceolate) and with distinct capitate apices. Both N. taylorii and N. solita have the same areolate morphology on the valve face and keel. Nitzschia taylorii is distinguished from N. steynii Cholnoky (1966: 207) by its lanceolate shape, the broader fibulae and finer striae. Nitzschia taylorii is less similar to N. frustulum ( Kützing 1844: 63) Grunow (in Cleve & Grunow1880: 98) and distinguished by its lanceolate shape with protracted capitate apices, uniseriate striae (not biseriate) on the keel. Further N. frustulum is presented with an interrupted raphe ( Fig. 19 ), where as N. taylorii is characterized by an uninterrupted raphe ( Fig. 18 ). Specimens of N. frustulum sensu lato, identified from brackish-like waters, have also been identified from the type locality of N. taylorii .

Four other taxa, N. costei Tudesque, Rimet & Ector (2008: 485) , N. macedonica Hustedt (1945: 946) , N. tropica Hustedt (1949: 147) and N. liebethruthii Rabenhorst (1864: 157) have similar valve outlines, approximate stria densities and fibula structure. In LM observations these taxa could be confused. In SEM, the differences between taxa were distinguished by valve outline ( N. tropica ), areolae formation on the keel ( N. macedonica , N. tropica , N. costei ), valve surface relief ( N. macedonica ), silica nodules on the mantle side of the keel ( N. taylorii ) and cingulum structure ( N. tropica , N. costei ) (compare Table 1).

Figures

FIGURES 1–12. Light microscopy of Nitzschia taylorii sp. nov. Figs. 1–9. LM of valve view showing the size diminution series. Figs. 10–12: LM of girdle view. Fig. 7 = holotype. Scale bars = 10 µm. (Specimens from holotype slide CESH-5-1881)

FIGURES 13–19. SEM micrographs of Nitzschia taylorii sp. nov. Fig. 13. SEM of external view of the entire valve. Fig. 14. SEM of girdle view showing valve bands. Fig. 15. SEM view of valve apex with deflected raphe terminal. Figs 16–17. SEM external view of raphe, valve mantle and areolae structure. Fig. 18. SEM of external view of central area of N. taylorii showing uninterrupted raphe. Fig.19. SEM of external view of central area of N. frustulum showing interrupted raphe. Scale bar in Figs 13, 14 = 10 µm; Figs 15–19 = 2 µm. (Specimens from sample CANA 85055)

FIGURES 20–26. SEM micrographs of Nitzschia taylorii sp. nov. Figs 20, 21. SEM of external girdle view showing valve bands. Fig. 22. SEM external view of areolae structure. Fig. 23. SEM internal view of entire valve. Fig 24. SEM internal view of valve apices. Fig. 25. SEM internal view showing round to rectangular shape fibulae. Fig 26. SEM external valve view showing basal margin scattered with small papillae (note arrow mark). Scale bars in Figs 20, 21, 26 = 2 µm; Figs 22, 24, 25 = 1 µm; Fig. 23 = 10 µm. (Specimens from sample CANA 85055)