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Photocycle-Dependent Emergence by Cercariae of Halipegus occidualis from Helisoma anceps, with Special Reference to Cercarial Emergence Patterns as Adaptations for Transmission.
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- Author(s) / Creator(s)
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Emergence by cercariae of Halipegus occidualis (Hemiuridae) from naturally infected Helisoma anceps (Pulmonata) was evaluated with respect to change in temperature and light. Total cercarial emergence per snail per day increased with temperature in 2 experiments: at constant temperatures of 16, 22, and 28 C, and at temperatures varying within the range 15-30 C. The number of cercariae emerging per snail per day varied extensively among snails and from day to day for individual snails. The proportion of cercariae that emerged during darkness in each 24-hr period on a 12-hr light: 12-hr dark photocycle was consistent for each snail over 3 photocycles, but it varied among snails: a mean of 73% of cercariae emerged during darkness at 16 C, 84% at 22 C, and 89% at C. The ecological consequences of nocturnal emergence by sessile, long-lived cercariae, such as those of H. occidualis, are discussed with reference to 3 hypotheses: synchronization with activity of the next host, enhancement of dispersal, and reduction of mortality.
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- Date created
- 1990
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- Subjects / Keywords
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- Type of Item
- Article (Published)
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- License
- Copyright American Society of Parasitologists 1990