Cocconeis sp. 1

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 : 10

Cocconeis sp. 1

( Figs. 106-109)

Valves elliptic, ends rounded. Valve with raphe: axial area linear and narrow, central area narrow, raphe filiform. Striae delicate interrupted by submarginal hyaline line. Valve without raphe: axial area linear and narrow. Striae slightly radiate. Areolae inconspicuous. Length: 9-11 μm; width: 5.5-6.0 μm; striae 24-26 in 10 μm in both valves. This taxon differs from other Cocconeis Ehrenberg species by the very small dimensions and the presence of delicate striae, hardly visible in LM.

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

Cymbellales Mann 1990 Gomphonemataceae Kützing 1844

Gomphonema brasiliense ssp. pacificum Moser, Lange-Bertalot & Metzeltin, Biblioth. Diatomol. , 38: 185, pl. 50, figs. 1-6. 1998.

( Figs. 126-128)

Valves heteropolar, narrowly lanceolate. Apical and basal ends attenuate-rounded. Axial area wide and lanceolate, central area indistinct. Raphe straight, with proximal ends, slightly dilated to pores. Transapical striae short, parallel to radiate toward the ends. Stigma absent. Length: 21-31μm; width: 3.5-5.3 μm; striae 13-14 in 10 μm. Gomphonema brasiliense ssp. pacificum resembles G. brasiliense concerning shape valve and the short striae. G. brasiliense ssp. pacificum differ morphologically by the presence of ends more attenuate and lower valve dimensions, mainly the width values ( Metzeltin et al. 2005). This taxon was registered in Brazilian studies of Marquardt & Bicudo (2014) and Medeiros et al. (2018).

Material examined: BRAZIL, MATO GROSSO DO SUL: Taquaruçú, Patos Lake , 23.III.2018, sediment, D. T. Ruwer (Nupélia UEM - 18099-106, 18109, 18113-122) .

Occurrence: first citation for Upper Paraná River floodplain.