Hatching and survival characteristics of Cyathocotyle bushiensis Khan 1962 (Digenea) eggs and miracidia

Cyathocotyle bushiensis Khan 1962 is a digenean intestinal parasite of ducks that appears to be involved in seasonal mortality of the definitive host. Temperature dependence of egg hatching and miracidial survival at 25 degrees C were experimentally investigated as part of a study on transmission of the larval stages. Maximum percentage of hatching was obtained at a temperature of 25 degrees C, at which the average hatching time was 21.7 days. The average hatching time decreased linearly from 38.9 days to 9.8 days between 18 and 28 degrees C. Eggs exposed to cold (4 degrees C) prior to incubation at 25 degrees C were significantly less successful in hatching than fresh eggs incubated at the same temperature. Their hatching percentage was much reduced and their average hatching time was increased. Similarly, eggs collected in late autumn (as opposed to summer) and incubated at 23 degrees C had significantly lower hatching success and significantly increased average hatching time. At 25 degrees C, the average life-span of the miracidia was 8.8 h. These results are compared with similar data from other digenean species and their significance is discussed in relation to transmission to the first intermediate host in climatic conditions prevalent in endemic areas.