Morphology, Biometry and Ecology of Arcella excavata Cunningham, 1919 (Rhizopoda: Arcellinida)

Abstract

Summary. Testate amoeba Arcella excavata Cunningham, 1919 , isolated from the aeration tanks of the Sofia's Wastewater Treatment Plant and its morphology, biometry and ecology have been investigated. Based on the rich live material (120 specimens), a detailed morphological description of A. excavata and new data about the cytoplasm and the nuclei of the species are supplied. It was found out that A. excavata is a multinuclear species and the nuclei are usually 3 or 4, rarely 5-6 (1-2% only). These new data, as well as the characteristic shape of the shell and its bigger depth, show clearly that A. excavata is a separate, well distinguishing species. The size frequency distribution analysis indicates that A. excavata is a size-monomorphic species, characterized by a main-size class and a small-size range (all measured individuals have a shell length of 60-70 µm and 98% have a shell breadth of 55-66 µm). The present study shows that A. excavata inhabits polluted waters also and this fact does not confirm the conclusion of Snegovaya that it can be used as a bioindicator of the waters with the saprobity β-α. Probably, it is also a freshwater eurybiont as well as the majority of the known species of family Arcellidae