Luticola gandhii (H.P.Gandhi) A.Kale, Levkov & B.Karthick, 2017

Kale, Aditi, Levkov, Zlatko & Karthick, Balasubramanian, 2017, Typification of two species of Luticola (Bacillariophyta) from aerophilic habitats of the Western Ghats, India, Phytotaxa 298 (1), pp. 29-42 : 33-37

Luticola gandhii (H.P.Gandhi) A.Kale, Levkov & B.Karthick comb. nov., nom. nov. stat. nov. ( Figures 27–51 )

Basionym:— Navicula charlatti v. lanceolata H.P. Gandhi 1970, p. 770 , Figs 52–56 (Gandhi, H.P. (1970) A further contribution to the diatom flora of the Jog-Falls, Mysore State, India. Beihefte zur Nova Hedwigia 31: 757–813.)

Lectotype (designated here):—[illustration] Fig. 54 in Plate II in Gandhi (1970) (here reproduced as Fig. 29 ).

Locus typicus:— INDIA, Karnataka, Jog Falls. Sample collected from encrustations on wet rocks along with some bryophytes and podostemonads, floating flakes of green matter and the brownish scum from pools, puddles and sheltered ditches near Jog-Falls (14.1758 °N, 74.8460 °E)

Epitypus (designated here):— Slide 03–36 from epilithic material #118 collected from a wet wall near Mahabaleshwar (17.91943 °N, 73.63112 °E), elevation– 1197 m, deposited in Diatom Collection at AHMA, Agharkar Research Institute, Pune, India. (the valve representing the epitype is Fig. 38 ).

Isoepitypus:— Slide 03– 35 in AHMA.

Description:— The valve outline is lanceolate to linear-lanceolate and transapically asymmetrical in some valves. Apices protracted in larger specimens to narrowly rostrate in smallest specimens. The valve length ranges from 16–45 μm and valve width from 6–9 μm (n = 50). Valve face is uneven. Axial area is narrow, linear, elevated and slightly curved along raphe at centre and raphe branches are straight ( Figs 44, 48 ). Central area is bow-tie shaped with grooves on both sides of proximal raphe endings ( Figs 44, 46, 48 ). Central area bordered with 2–3, isolated, round, smaller areolae located near the valve margin ( Fig. 46 ). Several (4–5) irregular depressions that do not penetrate the valve interior are present in the central area. A single, isolated and round stigma is located between valve centre and margin ( Fig 46 ). Raphe branches are positioned on a distinct raphe sternum. Externally, distal raphe endings are hooked, first deflected on same side as proximal ends and then hooked towards opposite side continuing towards valve mantle ( Fig. 48 ). Proximal ends are short, rounded and deflected away from the stigma ( Figs 44, 46, 48 ). Transapical striae are punctate, radiate throughout 15–21 in 10 μm ( Figs 44, 48 ). Transapical striae are composed of 5–6 areolae. The areolae are variable in shape, larger near the valve margins ( Fig. 44 ). Mantle striae composed of 2–3 rows of areolae ( Fig. 48 ). Girdle band with a single line of small round poroids ( Fig 48 ).

The internal structure shows areolae occluded by hymenes, forming a continuous strip across the valve. A narrow indistinct marginal channel is present at valve face/mantle junction, and is occluded by a hymen ( Fig. 49 ). Central nodule forms a stauros. Stigma is an indistinct opening bordered with a large, circular and lipped structure with a small notch ( Fig. 50 ). Raphe slit is simple and straight with proximal endings slightly deflected away from the stigma ( Fig. 50 ). Distally, the raphe ends in small helictoglossa ( Fig. 51 ). Internal valve apices, clearly showing the pseudosepta ( Figs 49, 51 ).

Etymology:— Named in honor of H.P. Gandhi, for his contributions to diatom research in the Western Ghats. Further, having separated Navicula charlatii var. lanceolata from L. charlatii and raising its rank to species, the epithet “ lanceolata ” is no longer available as it will be a later homonym of Luticola lanceolata (Freng.) Levkov, Metzeltin & Pavlov (2013: 150) . Therefore, the new name Luticola gandhii is proposed.

Distribution:— This aerophilic species was originally described from the Central Western Ghats (12– 16°N) by Gandhi and currently from the Northern Western Ghats (16– 21°N). However, to date samples outside the Western Ghats region do not document this species. Hence L. gandhii is possibly endemic to the Western Ghats.

Ecology:— Gandhi described these taxon from encrustations on wet rocks along with some bryophytes and podostemonads, floating flakes of green matter and the brownish scum from pools, puddles and sheltered ditches. The present study recorded L. gandhii from epilithic material on a wet wall in spray-zone of a waterfall. The water quality recorded for the wet wall was pH = 6.59, electrical conductance = 30.7 μS/cm, water temperature = 19.8°C, dissolved oxygen = 8.3 mg /L, and nitrate = 1.0 mg/L.

Figures

FIGURES 27–31. Luticola gandhii (Gandhi) A.Kale, Levkov & B.Karthick, stat. nov., nom. nov. Illustrations (Plate II, Figs 52–56) for Navicula charlatti v. lanceolata Gandhi scanned from Gandhi (1970). 25–32. (scale bar 10 μm)

FIGURES 32-43. Light microscope images of Luticola gandhii from Mahabaleshwar (scale bar 10 μm)

FIGURES 44–48. SEM external view of Luticola gandhii from Mahabaleshwar (scale bars 2 μm)

FIGURES 49–51. SEM internal view of Luticola gandhii from Mahabaleshwar (scale bars 2 μm)