Staurosirella sp. 2

Ruwer, Daiane Trevisan & Rodrigues, Liliana, 2021, Sediment diatoms from Upper Paraná River floodplAiN lAKeS: New recordS, Iheringia, Série Botânica (e 2021012) 76, pp. 1-16 : 7-10

Staurosirella sp. 2

( Figs. 41-46)

Valves heteropolar, ovate to clavate. Ends rounded, with apices slightly subcapitate and bases attenuate. Axial area linear and narrow, central area absents. Striae parallel and alternated slightly radiate at the ends in some specimens. Length: 5.6 - 15.9 μm; width: 2.1-3.1 μm; striae 10-12 in 10 μm. The specimens documented resemble Pseudostaurosira clavatum Morales ( Morales 2002) in valve morphology. Staurosirella sp. 2 can be distinguished from this taxon by lower values of valve length and less attenuate ends. Staurosirella sp. 2 is similar to species from the Opephora Petit genus concerning valve shape; however, Opephora presents predominant marine habit ( Round et al. 1990).

Material examined: BRAZIL, MATO GROSSO DO SUL: Batayporã, Garças Lake , 21.IX.2017, sediment, D. T. Ruwer (Nupélia UEM - 18085-18097) .

Eunotiales Silva 1962

Eunotiaceae Kützing 1844

Eunotia cf. bidens Ehrenberg, Ber. K. Akad. Wiss. Berlin, 1841: 413. 1843.

( Figs. 69-71)

Valves with dorsal margin convex with two slightly prominent undulations, ventral margin slightly concave. Ends truncated, detached from the valve body. Striae parallel to radiate. Length: 33-76 μm; width: 10-13 μm; striae 10-14 in 10 μm. The population observed are consistent concerning some valve morphology features and dimensions with Eunotia bidens presented in Metzeltin & Lange-Bertalot (1998) and Metzeltin et al. (2005). However, the studied population was maintained as a conferatur due to variation in the morphology of the ends. E. bidens has subcapitate, obtusely rounded apices, and slightly detached.

Material examined: BRAZIL, MATO GROSSO DO SUL: Taquaruçú, Patos Lake , 23.III.2018, sediment, D. T. Ruwer (Nupélia UEM - 18098-122) .

Occurrence: first citation for Upper Paraná River floodplain.

Eunotia deficiens Metzeltin, Lange-Bertalot & García- Rodríguez, Iconogr. Diatomol, 15: 48, pl. 22, fig. 5. 2005.

( Figs. 47-49)

Valves with dorsal margin convex, and slightly concave ventral margin. Ends rounded, slightly subcapitate, not detached from the valve body. Striae are parallel to slightly radiate, equidistant, and more concentrated at the ends. Length: 30-63 μm; width: 7.5-9.5 μm; striae 8-11 in 10 μm. The studied population is consistent with the type of material described in Metzeltin et al. (2005). E. deficiens resembles E. luna var. aequalis Hustedt but they differing in valve dimensions and striae density. E. luna var. aequalis present larger width values (12.6-15.3), dorsal margin more convex, and higher striae density (12-14) ( Bicca et al. 2009, Metzeltin et al. 2005, Simonsen 1987).

Material examined: BRAZIL, MATO GROSSO DO SUL: Taquaruçú, Patos Lake , 23.III.2018, sediment, D. T. Ruwer (Nupélia UEM - 18098-99, 18101-122) .

Occurrence: first citation for Upper Paraná River floodplain.

Eunotia cf. neomundana Metzeltin & Lange-Bertalot, Iconogr. Diatomol. , 5: 69, pl. 19, figs 1-6, pl. 22, figs 1-3. 1998.

( Figs. 66-68)

Valves almost linear, with a slightly triundulate ventral and dorsal margins. Ends apiculate, cuneate-apiculate, and attenuate-rounded. Striae parallel to slightly radiate at the ends, equidistant. Length: 25.2-76.1 μm; width: 6-10 μm; striae 8-13 in 10 μm. The studied population is similar to the type material described in Metzeltin & Lange Bertalot (1998) however; specimens documented have lower values of length and width.

Material examined: BRAZIL, MATO GROSSO DO SUL: Taquaruçú, Patos Lake , 23.III.2018, sediment, D. T. Ruwer (Nupélia UEM - 18101-120) .

Occurrence: Paú Veio Lake , Upper Paraná River floodplain, ( Biolo & Rodrigues 2013) .

Eunotia papilio (Ehrenberg) Grunow, Alg. Novara , 94. 1868.

( Figs. 72-73)

Valves with dorsal margin convex with two prominent undulations, ventral margin tightly concave. Ends cuneate, dorsally deflected. Striae parallel to radiate towards the ends. Length: 25-35 μm; width: 7-12 μm; striae 8-10 in 10 μm. The population observed is consistent with specimens from Metzeltin et al. (2005) and Brazilian studies of Costa et al. (2017) and Oliveira et al. (2012). This taxon differs from other Eunotia species by the presence of two prominent undulations on the dorsal margin and cuneate ends.

Material examined: BRAZIL, MATO GROSSO DO SUL: Taquaruçú, Patos Lake , 23.III.2018, sediment, D. T. Ruwer (Nupélia UEM - 18098-18099, 18101-122) .

Occurrence: first citation for Upper Paraná River floodplain.

Eunotia rabenhorstii var. monodon Cleve & Grunow in Van Heurck, Syn. Diat. Belg., pl. XXXV, fig. 12B. 1881.

( Figs. 76, 77)

Valves with dorsal margin convex with an attenuatedrounded undulation in the middle region, ventral margin concave. Ends rounded, widely dilated. Striae parallel to radiate towards the ends. Length: 9.0-25.5 μm; width: 5-9 μm; striae 13-16 in 10 μm. E. rabenhorstii var. monodon resembles E. rabenhorstii var. triodon Cleve & Grunow , differ by the number of undulations on the dorsal margin. E. rabenhorstii var. monodon presents one undulation while E. rabenhorstii var. triodon has three undulations on the dorsal margin ( Van Heurck 1881). The specimens observed are similar to those registered by Costa et al. (2017).

Material examined: BRAZIL, MATO GROSSO DO SUL: Taquaruçú, Patos Lake , 23.III.2018, sediment, D. T. Ruwer (Nupélia UEM - 18098, 18101-102, 18104, 18106-107, 18109-111, 18113-121.

Occurrence: first citation for Upper Paraná River floodplain.