1. Department of Gametes and Embryo Biology; Institute of Animal Reproduction and Food Research, Polish Academy of Sciences; Tuwima 10, 10-748 Olsztyn Poland
2. Institute of Zoology; Jagiellonian University, Department of Comparative Anatomy; 30-387 Kraków Poland
3. Stanislaw Sakowicz Inland Fisheries Institute; Department of Pond Culture in Żabieniec; 05-500 Piaseczno 1 Poland
4. University of Warmia and Mazury; Department of Ichthyology; 10-718 Olsztyn-Kortowo Poland
5. Department of Hormonal Action Mechanisms; Institute of Animal Reproduction and Food Research, Polish Academy of Sciences; Tuwima 10, 10-748 Olsztyn Poland