Production characteristics of males and histological pattern of changes in gonadal structure in Siberian sturgeon after obtaining reproductive products

Abstract

The article focuses on the ‘preservation’ of sturgeon males at low temperatures in order to shift sexual cycles and slow down sperm production during the period required to organise the reproduction process. The study assessed the longterm effects of low temperatures on spermatogenesis, production characteristics, reproductive product quality, and spermatogenic waves in males at first and repeat maturity. Thirty male Siberian sturgeons were kept in a tank with water temperatures of 4–5.5 °C in January to April and 6.2–6.4 °C in May to June. The period from baseline to obtaining reproductive products was 133 days in Group 1, 153 days in Group 2, and 172 days in Group 3. Male maturation was stimulated using the generally established approach, with a switch to spawning temperature occurring within 10–14 days of the pre-spawn period. Sperm volume, concentration, motility, and relative fecundity were used to assess the quality of reproductive products. The longest-lived sperm was observed in males at first maturity in the second and third portions of sperm. The histological pattern of changes in the testes prior to hormone stimulation reflects the expected asynchrony in germ cell development. Complete resorption of overmature sperm by histiocytes and Sertoli cells was observed in all gonad sections after a pituitary injection and obtaining the fourth portion of sperm. Keeping males at low temperatures can significantly improve the quality of reproductive products for up to 172 days, with a thermal constant of 1,180 degree days. It is recommended that the time of hormone stimulation be shifted by 2 hours before the challenging injection in females. It allows the first portion of sperm to be obtained earlier, before the main work with spawners, and the second or third portion of sperm to be used in the reproduction process.