Haptoral hard part variability in Gyrodactylus teuchis Lautraite, Blanc, Thiery, Daniel & Vigneulle, 1999 (Monopisthocotyla: Gyrodactylidae) parasitizing cage-reared rainbow trout in Karelia

Variability of the marginal hooks of Gyrodactylus teuchis parasitizing rainbow trout Oncorhynchus mykiss (Walbaum, 1792) was studied in cage farms situated in water bodies of the Baltic and White Sea drainage basins. Differences between groups proved to be predicated on two characters – marginal hook total length (MHTL) and marginal hook sickle length (MHSL). The probability of correctly identifying a specimen as belonging to the White Sea or Baltic group relying on the discriminant function based on these predictors is 98.6%. Meanwhile, when the function was tested on the worms whose samples were not involved in discriminant analysis, its predictions were correct only in 73% cases. These results indicate substantial intraspecific variability in the above mentioned characters in G. teuchis.