Cyst-forming amoebae of the genus Korotnevella Goodkov, 1988 (Amoebozoa: Dactylopodida), with description of two new species

The genus Korotnevella Goodkov, 1988 (Amoebozoa: Dactylopodida) comprises amoebae with a complex cell coat that include a layer of scales covering the entire cell surface. Until now no Korotnevella species were known to form cysts. Here we describe two new species of genus Korotnevella and provide a light- and electron-microscopic report of encystment in three species (K. stella (Schaeffer, 1926) Goodkov, 1988, K. limbata n. sp. and K. heteracantha n. sp.) of this genus. Korotnevella limbata has two peculiar wide rims along the upper margin of basket scales forming two short spines at their junctions. The basket scales of K. heteracantha are very similar to those of K. bulla, but have a different spine length and a closed latticework basket with polygonal elements. All three studied species have similar cyst wall consisting of three layers. The outer layer contains scales of trophic stage; the middle one includes so called “cyst scales” with meshwork walls; and the inner one is composed of fibrillar material. Cyst structure of this sort appears to be unique for lobose amoebae and probably represents an autapomorphy for genus Korotnevella.