Luticola minutissima M. Rybak, Peszek, Skoczylas & Ludwig, 2022

Rybak, Mateusz, Peszek, Łukasz, Skoczylas, Łukasz & Ludwig, Thelma Alvim Veiga, 2022, A new small-celled diatom from Brazil - Luticola minutissima sp. nov., with comparison to the type of the Antarctic L. neglecta Zidarova, Levkov & Van de Vijver, Phytotaxa 530 (3), pp. 287-294 : 288-291

publication ID	https://doi.org/ 10.11646/phytotaxa.530.3.4
DOI	https://doi.org/10.5281/zenodo.5836013
persistent identifier	https://treatment.plazi.org/id/03AA879B-061A-4F01-0C81-8A4995F3FE26
treatment provided by	Plazi
scientific name	Luticola minutissima M. Rybak, Peszek, Skoczylas & Ludwig
status	sp. nov.

Treatment

Luticola minutissima M. Rybak, Peszek, Skoczylas & Ludwig , sp. nov. ( Figs 1–46 View FIGURE 1–37 View FIGURE 38–46 )

Type:— BRAZIL. Rio de Janeiro: city of Rio de Janeiro, Alto da Boa Vista, 22°57’09’’S, 43°13’40’’W, Ł. Skoczylas, 29 March 2015 (holotype UPCB! slide UPCB96.149 View Materials , Herbarium of the Departamento de Botânica da Universidade Federal do Paraná, Brazil , depicted in Fig. 19 View FIGURE 1–37 ). Isotypes : slide 26943 at the Szczecin Diatom Collection hosted by the University of Szczecin ( SZCZ); slide 2015/1/1 and cleaned material stored in the Diatom Collection of the Institute of Agricultural Sciences , Land Management and Environmental Protection at the University of Rzeszów GoogleMaps .

Description:— Valves elliptic-lanceolate to rhombic-lanceolate with narrowly rounded apices ( Figs 1–37 View FIGURE 1–37 ). Range of valve dimensions (n = 60): 5.2–16.8 μm long and 3.7–5.4 μm wide. Axial area linear, central area bow-tie shaped, bounded by 2–4 areolae. Elongated stigma present in the central area, located close to face valve margin ( Figs 38, 40, 42 View FIGURE 38–46 ). Internally, stigma with indistinct opening bordered with large, circular, and lipped structure ( Fig. 43, 45, 46 View FIGURE 38–46 ). Marginal channel evident in SEM ( Fig. 46 View FIGURE 38–46 ), not visible in LM. Raphe branches almost straight to slightly curved ( Figs 1–37 View FIGURE 1–37 , 39–41 View FIGURE 38–46 ). External proximal endings double curved, first deflected away from the stigma, next abruptly hooked at a 90-degree angle to the stigma side ( Fig. 29–42 View FIGURE 1–37 View FIGURE 38–46 ). Distal raphe endings hooked towards the stigma side, continuing onto the valve mantle ( Fig. 39–42 View FIGURE 38–46 ). Striae radiate, 22–28 at 10 μm, composed of 3–4 rounded areolae. Internally, poroids on valve face occluded by hymens, forming a continuous strip on each stria ( Fig. 44, 46 View FIGURE 38–46 ). Valve mantle has a single row of round areolae ( Fig. 30, 37 View FIGURE 1–37 ).

Etymology:— The species name minutissima (lat. –tiny, smallest) refers to the small size of the new species’ frustule.

Distribution and ecology:— The species was observed in terrestrial habitats (mosses and lichens overgrowing different substrates, i.e. a concrete wall and palm tree trunks), both in urban and forest areas. The species developed very rarely, in the form of individual valves in the samples.

Together with Luticola minutissima sp. nov., the most frequent species in sample 2015/1 were Humidophila sp. (90.3%) and Achnanthes pseudoinflata M.Rybak, Peszek, Skoczylas, Ector & C.E.Wetzel (2020: 3) (7.4%), while in sample 2015/3 the most frequent were: Humidophila contenta (Grunow) Lowe, Kociolek, J.R.Johansen, Van de Vijver, Lange-Bertalot & Kopalová (2014: 357) (74.8%) and Luticola moreirae Straube, Tremarin & T.Ludwig (2017: 428) (17.9%). In sample 2015/2 no dominant species were designated, due to an extremely low number of valves (15–30 per slide).

Additional observation of Luticola neglecta Zidarova, Levkov & Van de Vijver is presented ( Figs 47–67 View FIGURE 47–67 ). The observed valves (n = 30) correspond to the description in Zidarova et al. (2014, 2016) in most morphological features. Notwithstanding, some additional observations were made. The external shape of stigma in the mentioned papers is small and rounded, but from our observations, it also seems to be slightly elongated ( Figs. 61, 63, 64 View FIGURE 47–67 ). The internal valve view ultrastructure has not been described until now. The areolae of the valve face are occluded by hymenes, forming a continuous strip on each stria. A marginal channel is visible internally under SEM, and is occluded by hymen. Internal stigma opening is small and C-shaped.