CHROMOSOME SETS OF TRICHOBILHARZIA SZIDATI AND BILHARZIELLA-POLONICA (SCHISTOSOMATIDAE, TREMATODA)

The diploid number of chromosomes of T. szidati and B. polonica equals 16. Karyotype structure of T. szidati is as follows: 1,5,8 m+2,6,7 sm +3 st-sm+4 sm-m, that of B. polonica is 1 Z st, 1 W sm+2,8 m+3,7 sm-m4,6 sm+5 m-sm. The absolute length of chromosomes of T. szidati is fro m 3.41 to 8.71 mum, that of B. polonica from 2.48 to 9.48 mum. The rel ative length of Z chromosomes constitutes 23.26, W - 9.79 % of the tot al haploid set length of B. polonica. It is noteworthy that the level of sex chromosomes differentiation is similar to that of the schistoso mes of the genera Schistosomatium, Heterobilharzia and Austrobilharzia .