Taxonomia de duas espécies do gênero Stauroneis de um lago de inundação amazônico (Belterra, Pará, Brasil)

Abstract

The genus Stauroneis is characterized by having two plastids, mostly lanceolate to elliptical valves, uniseriate striae composed of rounded or transversely elongated areolas and the occasional presence of apical pseudosepta. These organisms live in fresh water and are epipellic, some aerophytic and periphytic in mosses. The objective of this work is the description of two species of the genus Stauroneis found in Lake Jurucuí, based on discriminated observations of light and scanning electron microscopy, comparing them with similar species of the genus. The research was based on samples collected in June 2018 at four initiation stations, starting in sediment, plankton and periphyton. Samples of planktonic material were collected with a plankton net with a 20 μm mesh, and the periphytic material by scraping the submerged parts of macrophytes using brushes and sticks. Sediment samples were collected at all stations with a “Core” type sampler. When comparing Stauroneis sp.1 with the following species: Stauroneis gracilior (Rabenhost) Reichardt (1995), Stauroneis neohyalina Lange-Bertalot & Krammer (1996) and Stauroneis margaritorae H. Lange-Bertalot (2003), Stauroneis sp. 1 had a more pointed apex and a more rectangular stature, which differs from future projections. We compared Stauroneis sp. 2 with the following species: Stauroneis bicuneata Metzeltin & Lange-Bertalot (2007) and Stauroneis schinzii var. Argentina Frengelli. The specimens of the species Stauroneis sp. 2 had a straight valve shape different from advanced species that have a slightly curved valve shape. The results obtained for phycological studies, in addition to expanding knowledge regarding the genus Stauroneis, which are still so little observed in the Amazon region. Therefore, we emphasize that there are no records of the species found in any other work, thus, based on the analyzes of the material in optical microscopy and electronic microscopy of tracking, we conclude that they are new species.