Euastrum abruptum Nordst.

Euastrum abruptum Nordst. ( Fig. 3E View FIG )

Videnskabelige meddelelser fra Dansk naturhistorisk forening i Københaven 21 (14-15): 217 ( Nordstedt 1870).

Euastrum subglaziovii Borge, Öfversigt af Kongliga Vetenskaps-Akademiens Förhandlingar 56 (7): 25 ( Borge 1899).

DISTRIBUTION. — Cosmopolitan.Amazon Basin: Thomasson (1977); Lopes & Bicudo (2003); Melo & Souza de (2009); Cadima (2013); Feitosa et al. (2015). Western Amazonia (lowlands): Araujo (2003); Díaz-Olarte & Duque (2009).

DESCRIPTION

Cells 44.7-46.1 µm long, 28.0-33.0 µm wide, isthmus 7.4-8.6 µm, apex 28.0 µm; cells 1.3-1.6 times longer than wide. Cells with an open median sinus in the distal portion. Semicells sub trapeziform, three-lobed, ornamented with submarginal spines and granules, each basal lobe with one median protrusion with three large tubercular granules, basal corners with one marginal spine. Apical lobe truncated, with a deep medium incision. Axial chloroplast.

REMARKS

Specimens from the Ecuadorian Amazon coincided with the description given by Prescott et al. (1977) and with populations for the Brazilian Amazon by Lopes & Bicudo (2003), Mato Grosso State in Brazil ( Camargo et al. 2009), and for the Upper Parana River ( Moresco et al. 2015). However, specimens fromMoresco et al. (2015) are slightly wider than ours. Other similar varieties, such as Euastrum abruptum var. subglaziowii , described in Krieger (1937) and Prescott et al. (1977), and also recorded by Moresco et al. (2015) for Brazil, can be separated apart from the type variety by its size proportions (smaller cells) and ornamental characters (no large granules on lateral protrusions of basal lobes).