[A population analysis of the variability of the hooklets in the cestode Triaenophorus crassus].

The paper presents data on the variability of attachment organs in the cestode Triaenophorus crassus, a parasite of freshwater fishes. The greatest range of variability of all the characters is typical of whitefish, a fish with a long life cycle, while the shortest one is characteristic of vendace and young of trout. It is suggested that the stay of the parasite in fishes, associated with host age, is accompanied by the increase in average sizes of hooks and variability range. Such an approach together with the analysis of hooks variability gives the possibility to estimate the participation of secondary intermediate hosts in the circulation of the parasite in the water body.