Behavioral responses of Poecilia vivipara (Osteichthyies: Cyprinodontiformes) to experimental infections of Acanthocollaritrema umbilicatum (Digenea: Cryptogonimidae)

► The swimming behavior of Poecilia vivipara was evaluated using an image analysis system comparing laboratory-reared uninfected fish before and after experimental infection with different intensities of cercariae of the trematode Acanthocollaritrema umbilicatum. ► The swimming behavior of Poecilia vivipara changed due to the intensity-dependent influence of metacercariae of A. umbilicatum, supporting the hypothesis that parasites are able to alter the behavior of their hosts. ► The fish intermediate host P. vivipara at first becomes slightly agitated, with a decrease in the time spent resting, but, as the intensity of the metacercariae increases, the resting time becomes more extended with a corresponding decrease in all movements, including the average speed. A lethargic and less motile fish may be more likely to be preyed upon by a lie-in-wait definitive host, such as the common snook Centropomus undecimalis.