Transmission of Cyclocoelum mutabile (Digenea) to snails: the influence of temperature on the egg and miracidium

MCKINDSEY, C.W., and MCLAUGHLIN, J.D. 1994. Transmission of Cyclocoelum mutabile (Digenea) to snails: the influence of temperature on the egg and miracidium. Can. J. Zool. 72: 1745 175 1. This study examined the survival and hatching dynamics of eggs of the digenean Cyclocoelum mutabile and the survivorship and infectivity of the miracidia under different temperature regimes. Hatching did not occur at or below 12°C. Hatching success was similar at 14, 16, and 20°C (69 -73 %). Two peaks in hatching were seen. Most eggs hatched within 12 h following immersion in water; a smaller hatching peak occurred about 24 h later. Storing eggs at 12°C for up to 4 weeks prior to raising the incubation temperature to 14°C had no effect on hatching success. However, hatching success was dependent on the source of the eggs. Between 62 and 71 % of the eggs from faeces and 90-98% of the eggs dissected from flukes hatched under the same protocol. Miracidia hatching from eggs stored for 0-7 weeks at 7°C prior to hatching at 14°C did not differ in their infectivity to snails (75 -86%). The survivorship of miracidia was higher at lower temperatures and when they were obtained from eggs dissected from the fluke. The longer survival and prolonged infectivity of miracidia at lower temperatures produced the highest transmission efficiency at 14°C. These results are discussed in relation to the seasonal transmission and ecology of the fluke.