ECOLOGY OF FREE-LIVING STAGES OF OSTERTAGIA-CIRCUMCINCTA

Callinan A. P. L. 1978. The ecology of the free-living stages of Ostertagia circumcincta. Internationaljournal for Parasitology 8: 233-237. The development and survival of the free-living stages O. circumcincta was studied in western Victoria in 1974-1976. For all plots in which development occurred, pre-infective larvae (L1-L2) were recovered within 0-8 days, infective larvae (L3) within 7-30 days and L3 on herbage and soil within 4-27 days. The mean minimum development time to L3 on herbage and soil was 14·3 ± 3·5 days and the mean development time to maximum yield of these was 33·3 ± 6·3 days. There were no distinct differences in development rates between plots. Plot yields of L3 on herbage and soil varied inversely as the mean of daily temperatures for the period until maximum yield of these. Yields varied from 0 to 16% of the number of eggs put out on each plot and highest yields were obtained from eggs put out during late autumn-winter. No L3 were observed to survive over summer. The migratory habits of L3 were such that a mean of 75·1 ± 5·6% of L3 on herbage and soil were actually on herbage; the soil was always a significant source of L3. © 1978.