GENERATION TIMES OF EPIDINIUM CAUDATUM AND ENTODINIUM CAUDATUM, DETERMINED IN-VITRO BY TRANSFERRING AT VARIOUS TIME INTERVALS

Generation times were determined in vitro with a pure culture of Epidi nium caudatum and a mixed culture of Epidinium caudatum and Entodinium caudatum. Measurement of logarithmic growth from a small inoculum for Epidinium caudatum alone, or in coculture, resulted in generation tim es of 30.8 and 19.5 h, respectively. Epidinium concentrations, either alone or in coculture, were maintained when cultures were transferred every 12 h; however, concentrations decreased rapidly with transfers a t 4, 6, or 8 h. For Entodinium caudatum, a generation time of 16.3 h w as obtained from measurement of logarithmic growth. Based on sequentia l transfer data at varying time intervals, Epidinium caudatum and Ento dinium caudatum seem to be capable of doubling in approximately 12 to 13 h. These values are markedly less than those previously reported an d help explain the ability of these protozoa to maintain themselves in the rumen.