Infestation by the freshwater cymothoid Artystone trysibia Schioedte (Crustacea,Isopoda): parasite and host behaviour

To observe the behaviour of cymothoid isopods during the infestation process, 30 experiments in aquaria were carried out, using the fish Gymnogeophagus gymnogenys (Hensel, 1870) and Jenynsia multidentata (Jenyns, 1842) as hosts, and Artystone trysibia Schioedte, 1866 as the parasite. All the specimens were collected from Guaíba Lake in Porto Alegre, Rio Grande do Sul. We recorded and analysed the behavioural acts of the parasites and hosts from the moment of encounter to the infestation, which was considered to be completed when the parasite had inserted itself into the fish's body. The behavioural acts are shown as a flow diagram, including the frequencies of occurrence of each act. Positive infestation occurred in 60% of the experiments. No relationship was observed between the sizes of the parasite and host, and the success of the infestation.