The influence of oocyte maturational stage on hatching and triploidy rates in hybrid (bester) sturgeon, Huso huso×Acipneser ruthenus

We have investigated the relationship between maturational competence and hatching rate of eggs ovulated following injection of lutenizing hormone releasing hormone ethylamide (LH-RHa) in the cultured hybrid (bester) sturgeon (Huso huso female×Acipenser ruthenus male). Among 10 steroids tested (including progesterone) in a previous study, 17α-hydroxyprogesterone (17αOHP) was the most potent inducer of final maturation in the bester, with results similar to 17α,20β,21-trihydroxy-4-pregnen-3-one and 17α,20β-dihydroxy-4-pregnen-3-one. We therefore used 17αOHP to estimate maturational competence in the present study. In vitro oocyte maturation response to 17αOHP at a concentration of 0.1 μg/ml was correlated with ovulatory response to hormone treatment and quality of ovulated eggs. Two females exhibited higher in vitro oocyte maturation rate (100% germinal vesicle breakdown), ovulated sooner after hormone injection, and also had a higher hatching rate (77, 92%). In the F2 bester broodstock with a lower hatching rate (10-21%), a higher incidence (15-64%) of spontaneous triploidy was found. These results indicate that maturational competence can be estimated by in vitro oocyte maturation response to 17αOHP at 0.1 μg/ml and that this is a useful technique for selecting the proper female for breeding. Ovulatory success, hatching rate and occurrence of triploidy are thus all predictable in the cultured bester.