The effect of octopaminergic compounds on the behaviour and transmission of Gyrodactylus

Although transmission routes in gyrodactylids have been studied extensively, the behaviour of individual parasites has received little attention. Specimens of Gyrodactylus gasterostei Gl？ser, 1974 and G. arcuatus Bychowsky, 1933, were collected from the skin of their host, the three-spined stickleback (Gasterosteus aculeatus L.), and permitted to attach to the substrate. The movements of individual parasites were recorded and analysed.The behaviour patterns of the two species were similar and parasites were more active in red light and darkness than in white light. Four octopaminergic compounds were tested and all four inhibited the movements of parasites. Treatment ultimately led to death at low concentrations (0.2 μM), although prolonged exposure was necessary in some instances.Octopaminergic compounds may affect the parasite's ability to locate and remain on its host and these or related compounds might provide alternative or supplementary treatments for the control of G. salaris infections. With more research there is potential for use of octopaminergic compounds, which have minimal effects on the host or its environment, as parasite-specific treatments against G. salaris infections.As Gyrodactylus von Nordmann, 1832 (Monogenea) has no specific transmission stage in its life-cycle, movement between hosts must be achieved by strategies employed by the adult. Bakke et al. [1] suggested four routes by which gyrodactylids could transfer to a new host: (i) via contact with live hosts, (ii) via dead hosts, (iii) by detached parasites drifting in the water column, and (iv) by parasites attached to the substrate. This transmission potential, coupled with their high fecundity allows gyrodactylids to rapidly colonise new river systems [1,2]. Although transmission routes in gyrodactylids have been studied extensively, few workers have investigated the behaviour of individual gyrodactylids.Gyrodactylus salaris Malmberg, 1957 has devastated Atlantic salmon (Salmo salar L.) p