Variability and phenotypic structure of Proteocephalus torulosus (Cestoda: Proteocephalidea)--a parasite of cyprinid fishes

Variability of 5 qualitative features of Proteocephalus torulosus from 6 fish species belonging to 5 genera of the subfamily Leuciscinae was studied. Itraspecific diversity is represented by 3 scolex forms, 2 types of proglottid structure, 3 proglottid shapes, and 2 variations of the female reproductive system characteristics. The parasite living in different host species form separate ecological forms differing in the number of phenotypes and their ratio. However, the same scolex and strobila phenotypes dominate in the range of the parasite. Two P. torulosus groupings have been recognised the European and Asian ones, which differ in the representation of the proglottid structure types.