DIFFERENT LEVELS OF A LACK OF X-Y CHROMOSOME PAIRING PACHYTENE SPERMATOCYTES OF RED FOX (VULPES VULPES) AND CHINESE RACCOON DOG (NYCTEREUTES PROCYONOIDES PROCYONOIDES)

Research was performed on pachytene spermatocytes obtained from 8 male raccoon dogs and 10 male red foxes. Cells were immunostained for visualization of synaptonemal complexes and sex chromosome chromatin. Fluorescent microscope analysis revealed lack of pairing between the sex chromosomes. Additionally, synaptonemal complex structures formed by the B chromosomes and their number in cell were determined. The data showed a large difference in the level of X and Y chromosome pairing failure in the spermatocytes of both species analysed. The described phenomenon was observed in 15.6% of the Chinese raccoon dog spermatocytes and only once (0.2%) in the red fox spermatocytes. Among the raccoon dog males an interindividual difference in the level of sex chromosome pairing failure was observed. The numbers of B chromosomes observed in analysed cells varied from 2 to 5 in raccoon dogs and from 0 to 6 in red foxes. Different structures of the synaptonemal complexes of B chromosomes were observed such as univalents, bivalents, trivalents and tetravalents. The results of our research showed that with the increase in the number of B chromosomes in spermatocytes of the raccoon dog, the level of sex chromosome pairing failure increases.