Micrasterias laticeps Nordst.

Micrasterias laticeps Nordst.

( Fig. 4F View FIG )

Videnskabelige Meddelelser Dansk Naturhistorisk Forening 1870: 220 ( Nordstedt 1870).

Tetrachastrum americanum W. Archer , A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign: 725 ( Pritchard 1861). — Micrasterias disputata H. C. Wood , Smithsonian Contributions to Knowledge 19 (241): 142 ( Wood 1873).

DISTRIBUTION. — Cosmopolitan. Amazon Basin: Grönblad (1945); Thomasson (1971); Lopes & Bicudo (2003); Melo et al. (2005); Cadima (2013); Cunha de et al. (2013). Western Amazonia (lowlands): Krieger & Scott (1957); Montoya (1974); Duque & Donato (1993); Duque & Núñez-Avellaneda (1997); Araujo (2003); Duque & Núñez-Avellaneda (2000); Ortega et al. (2007); Núñez-Avellaneda (2008); Díaz-Olarte & Duque (2009).

DESCRIPTION

Cells 124.0-150.6 µm long, 162.0-197.1 µm wide, isthmus 40.1-44.5 µm; cells 1.3 times wider than long. Cells with a deep median constriction, central sinus closed near the isthmus and then opened; punctuated and hyaline cell wall. Semiorbicular semicell, three-lobed; interlobular incisions opened and deep, V-shaped; apices of the lateral and polar lobes facing to the opening of the sinus, polar lobes bigger than the lateral lobes, angles of the polar lobe acuminated and lateral lobes two-denticulated.

REMARKS

Although Bicudo & Sormus (1972) and Santos et al. (2016) mentioned that this taxon is highly polymorphic, especially in the curvature of the polar lobe and the opening of the interlobular incisions, specimens in our populations showed a conservative form.