ON THE HOST-SPECIFICITY OF FISH TAPEWORM PROTEOCEPHALUS-EXIGUUS LA-RUE, 1911 (CESTODA)

Host-parasite interactions established between Proteocephalus exiguus and its fish hosts have been analysed in two localities in Slovakia. P . exiguus occurred and sexually matured in three salmonid hosts - rain bow trout (Oncorhynchus mykiss), brown trout (Salmo trutta m. fario), brook trout/Salvelinus fontinalis) - and in perch (Perca fluviatilis), first recorded as a final host of this parasite. The parasite usually strictly prefered its principal, most suitable host (rainbow trout) o r some other salmonid hosts. The new fish host species (perch) harbour ed P. exiguus rather frequently, but only in altered ecosystem, ii sal monids were not available in sufficient number in the environment larg e adaptive ability of P. exiguus manifested in iis survival in four fi sh hosts of two distant families (Salmonidae, Percidae) and modified s easonality in unusual fish host indicate broader host specificity (ste noxenous in sense used by Euzet & Combes, 1980) than generally attribu ted to this species. The host specificity in some other Proteocephalus tapeworms is briefly discussed.