Platessa arborea C. Radhakrishnan, S. Sherly & B. Karthick, 2022

Sherly, Sheena, Radhakrishnan, Cheran & Karthick, Balasubramanian, 2022, Platessa arborea sp. nov. (Bacillariophyceae): A new tree moss dwelling diatom from the Eastern Himalayas, India, Phytotaxa 552 (2), pp. 151-158 : 152-153

publication ID	https://doi.org/ 10.11646/phytotaxa.552.2.2
DOI	https://doi.org/10.5281/zenodo.6709374
persistent identifier	https://treatment.plazi.org/id/172D051B-060F-A97E-0AEE-92FDFAD42620
treatment provided by	Plazi
scientific name	Platessa arborea C. Radhakrishnan, S. Sherly & B. Karthick
status	sp. nov.

Treatment

Platessa arborea C. Radhakrishnan, S. Sherly & B. Karthick sp. nov. ( Figs 1–67 View FIGURE 1–60 View FIGURE 61–67 , Fig. 9 View FIGURE 1–60 represents the holotype)

LM Description ( Figs 1–60 View FIGURE 1–60 ):—Valve elliptical with narrowly rounded apices. Raphe-sternum valve (RSV): Length: 6.5–9.5 µm, width: 3.5–4.5 µm, ratio length/width: 1.6–2.2 (n = 60). Axial area narrow and hardly discernible, visible only near center of the valve; central area nearly rectangular shape, bordered by 2–3 shorter striae frequently more widely spaced. Striae radiate throughout the valve, 22–24 in 10 µm. Raphe slightly filiform expanded proximal raphe endings.

Sternum valve (SV): wide axial area, Length: 6.0–9.0 µm, width: 3.5–4.5 µm. Striae densely arranged 22–24 in 10 µm, parallel at centre, radiate towards apices.

SEM Description ( Figs 61–67 View FIGURE 61–67 ):—Raphe-sternum valve (RSV): Externally, raphe filiform, slight curvature found near ends ( Figs 61 & 63 View FIGURE 61–67 ). Proximal raphe ends positioned in a broadened shallow groove, distal raphe located in the shallow groove with cone-shaped endings, and both ends slightly bend to the same side ( Fig. 61 View FIGURE 61–67 ). Striae mostly uniseriate; however found biseriate at 2–3 striae near apices. ( Fig. 61 View FIGURE 61–67 ). Areolae, apically slit-like throughout the valve, only at the center of the valve it is round-shaped towards axial area ( Fig. 61 View FIGURE 61–67 ).

Internally, proximal raphe ends are strongly hooked, a very remarkable feature which is infrequent in other Platessa species, and its distal ends are curved on opposite sides, terminating in well-developed helictoglossae ( Figs 64, 65 View FIGURE 61–67 ). Striae lowered between raised virgae. Width of the interstriae is wider than the striae. Striae internally rectangular to round in shape and mostly covered with hymen ( Figs 64, 65 View FIGURE 61–67 ). An apparent depression is observed on the central nodule ( Figs 64, 65 View FIGURE 61–67 ). Sternum valve (SV), externally, axial area covered with several irregular shape depressions distributed on the surface of the valve ( Fig. 62 View FIGURE 61–67 ). Striae uniseriate, however, found biseriate at more than 10 striae near the valve mantle ( Fig. 62 View FIGURE 61–67 ). Interstriae is raised, and the width of striae is unequal ( Fig. 62 View FIGURE 61–67 ). Internally, axial area is flat and features are not easily visible ( Fig. 66 View FIGURE 61–67 ). Biseriate striae found near the mantle with hymenated areolae. Interstriae raised its width slightly more than the striae ( Fig. 67 View FIGURE 61–67 ).

Holotype (designated here):—Slide #58/55, Sample #2878; deposited at the Diatom Collection, Agharkar Research Institute Herbarium ( AHMA), Pune, India. GoogleMaps

Type locality:— INDIA, Sikkim, composite tree moss sample collected on 22 November 2019 on the way to Khecheopalri Lake GoogleMaps , West Sikkim district (27.34829 °N, 88.19187 °E; elevation 1794 m a.s.l.) by Radhakrishnan Cheran.

Etymology:—Named after the habitat (tree) on which it was found. In Latin, the tree is called an Arbor.