Hatching of Echinostoma caproni miracidia from eggs derived from adults grown in hamsters and mice.

Echinostoma caproni eggs developed fully formed miracidia from hamster-source eggs in 9 days and from mouse-source eggs in 10 days under either light or dark conditions at 27 degrees C. Incubation of egg cultures under constant light resulted in miracidial hatching from hamster-source eggs in 11 days and from mouse-source eggs in 13 days. Exposure to light was essential to trigger hatching, with incandescent light providing more consistent stimulation than fluorescent light. A majority of the miracidia hatched at between 1100 and 1600 hours, indicating a diurnal circadian pattern. Eggs stored in a dark environment for 11 days required 6 days to reach maximal hatching after exposure to light. Eggs stored for 46 and 56 days hatched on the same day of their exposure to light. Miracidia that hatched after 56 days of dark storage exhibited aberrant swimming behavior; those stored in a dark environment for 70 days or longer did not hatch when exposed to light.

Responses of Echinostoma caproni miracidia to gravity, light, and chemicals.

In a four-tube vertical system, Echinostoma caproni miracidia exhibited a strong negative geotaxis which was dominated by a positive phototaxis. In horizontal chambers a positive phototactic response was also demonstrated. These miracidia showed a positive chemoresponse, as determined in phi-chambers, to glutamic and aspartic acids but not leucine. Positive responses were also elicited to snail-conditioned water and sulfuric and acetic acids. Ammonia, Mg2+, and HCl produced no significant reactions. Responses of E. caproni and Schistosoma mansoni miracidia, both of which develop in Biomphalaria glabrata snails, were similar providing further evidence that miracidia mimic the behavioral patterns of compatible snail species.