REVISION OF THE GENUS STENTOR-OKEN (PROTOZOA, CILIOPHORA) AND DESCRIPTION OF S-ARAUCANUS NOV-SPEC FROM SOUTH-AMERICAN LAKES

Stentor is a heterotrich ciliate which often forms lawn-like covers on the bottom and/or blooms in the pelagial of lakes worldwide. The spec ies involved in these spectacular events were usually either not deter mined or misidentified because the keys are outdated and incomplete. T hus. we have revised the nominal species described since the first maj or revision by Ehrenberg ( 1838). Main species characteristics are the presence/absence of symbiotic algae. the shape of the macronucleus an d the colour of the cortical pigment granules. The last character ment ioned must be studied in live cells because the pigment bleaches in ch emically fixed specimens. Nineteen valid species are recognized and di chotomously keyed according to these characteristics. Twenty-seven oth er species and varieties, described after Ehrenberg's revision, are sy nonyms or species indeterminata. A new species. S.araucanus, is descri bed from South American lakes. It is a small. broadly trumpet-shaped S tentor with symbiotic algae, vermiform macronucleus and blue-green cor tical granules. Stentor araucanus is probably euplanktic and restricte d to the southern hemisphere. Stentor auriculatus Kahl, 1932 sensu Wan g (1934) is recognized as a new species. Condylostoma wangi, and trans ferred to the genus Condylostoma. New nomenclatural corrections: Stent or baicalius nom. nov. (pro S.pygmaeus. preoccupied). S.loricatus nom. corr. (for S.loricata), S. ruber nom. corr. (for S. rubra).