The unisexusal-bisexual complex of spined loaches from genus Cobitis, occurred in the Moscow River, includes two tetraploid forms. One of them consists of males and females. The studies of spermatogenesis as well as spermatozoa mobility and ultrastructure, of these males were performed simultaneously with experimental crosses to define their reproductive capacities. The testis visually looked undeveloped in the most of cases. The study of spermatogenesis revealed that they reached the stage of starting spermatogenesis wave. The most cells were spermatocytes I or II. In some males, several seminal tubules were filled with connective tissue, displaced germ cells. Spermatozoa of tetraploid males looked unmoved under the light microscopy. The study of male gonads by electron microscopy revealed that the most of germ cells were destroyed. Normal spermatozoa were absent. Experimental crosses between gynogenetic triploid females and tetraploid males revealed that these males were capable to stimulate gynogenetic development, but not effective: only 4.7 % oftriploid eggs inseminated with sperm from tetraploid males survived up to hatching. But 56.6 % of obtained hatchlings normally developed and survived up to 58-days age.