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

Comparative graphics of Ambulatory time (seconds) of Poecilia vivipara before (▪) and after (▪) exposition to 50 cercariae of Acanthocollaritrema umbilicatum resulting in subgroups with 5-22 (N=16) and 23-36 (N=14) metacercariae. [Display omitted] ► 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. 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. Two experiments were performed, each with 30 fish which were individually exposed to 30 and 50 cercariae, respectively, shed from experimentally infected molluscs, Heleobia australis. Before and after (17–27days) infection, the behavior of each fish was monitored in terms of Distance travelled, Ambulatory time, Stereotypic time, Resting time and Average speed. At the end of the experiments, the fish were dissected to count the number of metacercariae recovered. In the experiment with 30 cercariae, fish with 2–10 metacercariae did not exhibit any significant differences in their swimming activity, but those with 11–22 metacercariae had a significantly enhanced Stereotypic time and a reduced Time Resting. In the experiment with 50 cercariae, fish with 5–22 metacercariae had an enhanced Distance travelled and a reduced Average speed; highly significant differences occurred with regard to all behavioral parameters when considering the subgroup 23–36 metacercariae: Distance travelled, Stereotypic time, Resting time, Ambulatory time and Average speed. Th