In vitro oocyte maturation and blood‐circulating steroid hormones in Sterlet ( Acipenser ruthenus ) and Siberian sturgeon ( Acipenser baeri )

Abstract

The oocyte of Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri) was evaluated after incubation with 17α, 20β-Dihydroxyprogesterone (DHP) in artificial media. Concentration of testosterone (T), progesterone (P4) and 17-β estradiol (E2) in blood and their relation to fertilization rate were measured during experimental period. The oocytes at the same developmental stages were incubated in SIS (based on sturgeon blood ionic composition), RM2 (Ringer solution modified for sturgeons) and L-15 (Leibovitz medium) artificial mediums in the presence of 1 μg/ml of 17α, 20β-Dihydroxyprogesterone for 12, 18 and 24 hr. The result of this study demonstrated that fertilization rate decreased with the increasing duration of incubation in all mediums. In the Siberian and Sterlet sturgeon, the highest fertilization rate was observed in the oocytes incubated in RM2 (0.81 ± 0.4) and SIS (0.44 ± 0.8) mediums for 12 hr respectively. In the Siberian sturgeon, fertilization rate decreased significantly (p < .05) with incubation time in all three mediums. In Starlet, fertilization rate decreased significantly (p < .05) with time and reached a minimum after 24 hr (0.16 ± 0.1) in L-15 medium. No significant (p > .05) differences were observed between blood plasma hormones and fertilization rate. The results of this study indicated that 17α, 20β-Dihydroxyprogesterone is essential for induction of in vitro oocyte maturation in these species.