Homing of Gyrodactylus salaris and G. derjavini (Monogenea) on different hosts and response post-attachment

The aim of our laboratory work was to elucidate the factors controlling host preferences and responses of congeneric monogeneans Gyrodactylus derjavini and G. salaris. We have established two parasite-host systems, G. derjavini on rainbow trout and G. salaris on salmon. Detached parasites were offered a choice in small aquaria between fry of rainbow trout, Atlantic salmon and carp. Within 48 hours more than 90 % of G. derjavini colonised rainbow trout and left salmon almost uninfected. Some parasites were found on carp. During the same time span, more than 60 % of G. salaris attached to salmon, the rest infected rainbow trout and none were found on carp. Following attachment, the parasites need appropriate stimuli to initiate feeding and reproduction but even such a successful specific colonisation can be followed by a host response. It was demonstrated by immunoblotting and immunocytochemistry that no antibodies in host mucus and host plasma bound to any parasite structures or epitopes.