STUDIES ON THE EVOLUTION OF THE OPHRYOSCOLECIDAE (CILIATA: OLIGOTRICHA): I. A NEW SPECIES OF ENTODINIUM WITH "CAUDATUM," "LOBOSO-SPINOSUM," AND "DUBARDI" FORMS, AND SOME EVOLUTIONARY TRENDS IN THE GENUS ENTODINIUM

Abstract

A new species of Entodinium—E. simulans—with an intraspecific variability similar to that of E. caudatum, is described. A parallel variability in E. rectangulatum is reported. It is shown that sets of the forms of the "caudatum," "loboso-spinosum," and "dubardi" types are produced by each of these three species of Entodinium. It is demonstrated that within the "caudatum–laterale" group of Entodinium there exists an evolutionary trend to the transformation of the left lateral groove into a narrow furrow, situated between the nuclear apparatus and the contractile vacuole.