Ninastrelnikovia lateritica S.Roy, Kociolek & B.Karthick, 2019

Roy, Surajit, Kociolek, John Patrick, Lowe, Rex L. & Karthick, Balasubramanian, 2019, Ninastrelnikovia lateritica sp. nov., a new and rare freshwater diatom species from the rocky pools of the Western Ghats, India with a note on the genus Ninastrelnikovia Lange-Bertalot & A. Fuhrmann (Bacillariophyta), Phytotaxa 394 (1), pp. 59-70 : 60-66

Ninastrelnikovia lateritica S.Roy, Kociolek & B.Karthick sp. nov. ( Figs 1–40 )

LM description ( Figs 1–14 ): —Cells forms colony, bilaterally symmetrical, biraphid. Chloroplast morphology unknown. Valves in valve view appear as narrowly elliptical or lanceolate, gradually inflated in centre. Ends subacutely or narrowly rounded. Length 13.5 – 17.7 μm, central width 3.8 – 4.1 μm, 1.1 – 1.5 μm at the valve apices. Raphe filiform and straight, proximal raphe ends moderately widely spaced, distal raphe ends appearing straight, not curved to the mantle. Axial area narrow, gradually widening towards an apically expanded elliptical central area. Striae distinct and prominent, transapical striae radiate in the valve centre and somewhat wedge-shaped, becoming sub parallel towards the ends, 15 – 16 in 10 μm.

SEM description ( Figs 15–40 ): —In external valve views ( Figs 15 – 28 ), two types of valves are noticeable. The first type of valve is located on the terminus of the colony and another type of valve is connected to the terminal valve towards the centre of colony. Valves terminating the cell colony ( Figs 15 & 16 ), show fully-developed straight raphe system along with longitudinally-oriented slender siliceous slat system. Instead of spines, this slat system forms pseudo-spines marginally. Another type of valve ( Figs 17 & 18 ) connected with the terminal valve, has a rudimentary vestige of the raphe and peripheral spatulate spines produced between striae. Marginal apical spines are more slender in comparison to other spines ( Figs 18 & 19 ). Slender siliceous slats are missing and spines are partly broken due to cleaning treatment ( Figs 17 & 18 ). Girdle view of a frustule with a terminal epitheca has a spine-bearing hypotheca ( Fig. 19 ). Both apices of terminal valve ( Figs 20 & 26 ) showing distal raphe ends extending onto the valve mantle and curved to the same side. Apex of intermediate valves ( Figs 21 & 27 ) reveals straight and reduced distal raphe ends. Apex of a colony-starting cell ( Fig. 22 ) shows the distal raphe end extending up to mantle, structure of pseudo-spines (arrows) and spatulate spines (arrowheads). Middle part of the terminal valve ( Fig. 23 ) has slightly dilated or expanded central raphe ends, but the central nodule is not visible in between proximal raphe ends and central area is devoid of a silica slat system. Middle part of the intermediate valve ( Fig. 24 ) has wedge-shaped, pleuriseriate striae and rudimentary proximal raphe end. Girdle view of the central area ( Fig. 25 ) shows the marginal spines (marked with arrowhead) and sporadically placed granules (round arrow). Another broken apex of the girdle valve ( Fig. 28 ) of a terminating cell shows the straight raphe fissure (arrow). Some striae in the valve centre are much larger than the others ( Figs 15, 17 & 18 ).

In internal valve views ( Figs 29 – 40 ), the raphe sternum is absent ( Figs 29 & 30 ). Valve shape variability is shown in Figs 29 – 32 . The proximal ends are deflected to the same side ( Figs 29 – 33 ) or appears straight due to weaklydeveloped nature ( Fig. 36 ), while the distal ends terminate as weakly developed helictoglossae ( Figs 29, 31 , 34 & 35 ). Internal valves of terminal and intermediate valves have the same set of characteristic features except for the proximal raphe ends. Terminal valve always shows unidirectionally placed proximal raphe ends ( Figs 29, 31 , 38 & 39 ). Presence of silica slat system on the outer side of the valves show these are terminal valve. Intermediate valves have both kinds of internal proximal raphe ends, hooked ( Figs 32 , 33 & 37 ) and straight ( Fig. 36 ). It is evident in Fig. 32 that another valve is attached (arrows) behind the intermediate valve. Valves shows interdigitating spines located on the valve and mantle junction and these spines support colony formation by interconnecting with adjacent valves ( Fig. 36 , aroows). However, the valves located inside the colony shows spines with limited growth ( Fig. 37 , arrows). The terminal valves have hooked ends only ( Figs 29, 31 , 38 & 39 ). Striae closed by reticulated pleuriseriate foramina ( Figs 36 , 37 & 39 ). Striae have openings that extend to the valve mantle ( Figs 29, 31 & 39 ). Strut-like structures are attached to the mantle ( Fig. 40 , arrows).

This biraphid, naviculoid taxon shows an assembly of terminal and intermediate valves. The cells are connected by their valve faces with the help of by marginal interdigitating spines ( Figs 19 , 32 & 36 ).

Type: — INDIA. Maharashtra: Rocky Pool in Kaas Plateau , 17.72635°N, 73.82249°E ; elevation 1224 m a.s.l., (holotype: AHMA! Individual in Slide No 02 – 097 from material #99, here illustrated as Fig. 11 ) .

Type habitat: —Dried Chara collected from a dried rocky pool.

Etymology: —The specific epithet is based on the habitat (iron rich, rocky substrate) of the new species at the type locality.

Figures

FIGURES 1–14. LM-micrographs of Ninastrelnikovia lateritica sp. nov., from the type population; valve views showing the size diminution series. Holotype depicted in Fig. 11. 3 & 4. Frustules in valve view with high and low focusing showing distinct raphe and central nodule. 8 & 9. Showing reduced raphes with wider spaced central endings (Scale bar represents 10 μm).

FIGURES 15–19. External views of Ninastrelnikovia lateritica sp. nov. frustules (SEM). 15 & 16. Face views of cell colony terminating valves bearing longitudinally oriented siliceous slat system. 17 & 18. Face views of intermediate valves of cell colony showing linking spatulate spines and wedge shaped pluriseriate areolae. 19. Girdle view of cell colony terminating frustule. (All scale bars represent 2 μm).

FIGURES 20–28. Detail of the external views of Ninastrelnikovia lateritica sp. nov. frustules (SEM). 20 & 21. Apices showing distal raphe ends of terminal and intermediate valves respectively. 22. Girdle view of the apex of a frustule showing pseudospines (arrows), spatulate spines (arrowheads) with distal raphe end curving towards the mantle. 23. Middle part of the terminal valve showing fully developed raphe system. 24. Middle part of the intermediate valve showing rudimentary raphe. 25. Girdle view of the middle part of a frustule showing pseudospines (arrow), linking spines (arrowhead) and silica granules (round pointer). 26 & 27. Apices showing distal raphe ends of terminal and intermediate valves respectively. 28. Another broken frustule apex showing raphe slit (arrow). (All scale bars represent 1 μm).

FIGURES 29–32. Internal views of Ninastrelnikovia lateritica sp. nov. frustules (SEM). 29–31. Whole valve showing striae pattern, central area, proximal raphe ends and narrowly elliptical valve shape with gradually swollen centre. 32. One terminal cell (arrows) connected with another intermediate valve that showing proximal raphe end. (All scale bars represent 3 μm).

FIGURES 33–36. Close up of internal valves of Ninastrelnikovia lateritica sp. nov. (SEM). 33. Proximal raphe ends strongly deflected onto the same side and internally open areolae. 34 & 35. Distal raphe end ending in helictoglossae. 36. Straight or rudimentarily developed proximal raphe end found in a intermediate valve which attached with another valve by interdigitating, long spatulate spines (arrows). (All scale bars represent 1 μm).

FIGURES 37–40. Close up of internal valves of Ninastrelnikovia lateritica sp. nov. (SEM). 37. Curved proximal raphe end found in a intermediate valve as it bears spines (arrows). 38 & 39. Curved proximal raphe end found in a terminal valve which shows slender siliceous slats (arrows). 40. A broken apical part showing strut like structures which holds the mantle. (All scale bars represent 1 μm).