Altered host behaviour in a cockroach-acanthocephalan association

Abstract

The effects of parasitism by the acanthocephalan Moniliformis moniliformis on the behaviour of two ecologically similar intermediate cockroach host species ( Periplaneta americana and Blattella germanica ) were compared. Open field activity, substrate orientation, substrate colour choice, photophilia, phototaxis and photokinesis were measured for infected cockroaches and uninfected controls in a series of laboratory arena experiments. Parasitism had significant effects on activity and substrate use, but not on photic responses. Compared with control animals, parasitized animals of both species showed a decrease in travel velocity and distance, and an increase in the use of horizontal surfaces. Other behaviour patterns were also altered by parasitism, but the direction and magnitude of the alteration depended on species, sex and light regime. Similar responses of the two species to parasitism may reflect common selective pressures on the host-parasite interaction, including ecological similarities of the host species and shared predators. Interspecific differences in the response to parasitism may reflect phylogenetic differences, physiological limitations, or constraints due to body size differences.