In vitro determination of generation times for Entodinium exiguum, Ophryoscolex purkynjei and Eudiplodinium maggii.

Most previously reported generation times for rumen ciliate protozoa are longer than would be required to prevent their being flushed out of the rumen. In an earlier study from this lab, using a sequential transfer procedure, generation times between 12 and 13 h were determined for both Epidinium caudatum and Entodinium caudatum. This would permit these species to be maintained in a rumen with a fluid volume turnover rate as rapid as twice a day. In this study, generation times were estimated for Entodinium exiguum (13.2 h), Eudiplodinium maggii (26.8 h), and Ophryoscolex purkynjei (29 h), by sequential transfer at both 12 and 24 h time periods. The generation time for E. exiguum is lower than reported for this and other Entodinium species as determined by logarithmic growth from a small inoculum, but similar to that obtained for Ent. caudatum using sequential transfer. Eudiplodinium maggii and O. purkynjei generation times are similar to previous estimates of 24- and 24-48 h, respectively. However, it was observed that after an adaptation period of 36 to 48 h (generally 3-4 transfers) cell concentrations decreased and generation times were markedly decreased, i.e. 12.2 h for Ent. exiguum, 15.0 h for E. maggii and 12.8 h for O. purkynjei. In a separate study, varying both the concentration of Epidinium and the quantity of substrate fed per cell had no effect on generation time.