Comparison of Hymenolepis diminuta WMS strain and WMS inbred line [IL1] at a time of intensified morphological variability of tapeworms

9-months tapeworms obtained from 3- 6-specimen populations of the 42nd generation of Hymenolepis diminuta WMS „strain" were compared with tapeworms obtained from quantitatively similar populations deriving from one-specimen infections of H. diminuta WMS il1. In both groups of tapeworms the majority of strobilas had unilateral position of genital pares (PGP), while the remaining ones were characterized by variable PGP. The latter appeared in 41.4% of H. diminuta WMS „strain" tapeworms and in only 24.6% of tapeworms coming from H. diminuta WMS il1. In tapeworms with unilateral as well as with variable PGP deriving from H. diminuta WMS il1, the average number of type 0p3a proglottids (all three testes on the aporal side) was significantly higher than in H. diminuta WMS „strain". It results most probably from suitable selection of mother specimens for successive generations of H. diminuta WMS il1. In both compared groups the growth of the number of PGP changes was correlated positively with the number of type 2p1a proglottids and negatively with the numer of type 1p2a and 0p3a proglottids.