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Interactions between metacercariae of Halipegus occidualis and ostracod second intermediate hosts (Cypridopsis sp.) were examined over 5 wk using female ostracods exposed to 4 cercariocysts each and maintained in isolation. Control ostracods were subjected to the same manipulations but were not exposed to cercariae. Growth of metacercariae over 4 wk was not constrained by either infection intensity or ostracod size. The number of eggs produced by ostracods was significantly reduced by the presence of metacercariae in an intensity-dependent manner. This reduction in reproductive output, combined with a significantly higher survivorship of exposed ostracods, suggests infection by H. occidualis may result in ostracod castration. These effects are considered to be the result of persistent ancestral traits rather than adaptation. |
