The 10th International Symposium on Sturgeon (ISS10)

The sterlet (Acipenser ruthenus) is an object of restocking, valuable aquaculture species and experimental model. However, its artificial reproduction often results in the unintentional production of individuals with species-atypical ploidy and impaired physiological/reproductive performance: autotriploids and haplo-diploid mosaics. We evaluated the effects of in vitro egg ageing and the fertilization environment on the incidence of ploidy abnormalities in sterlet to propose protocol that can ensure a good balance between ploidy structure and progeny yields. We conducted two experiments involving eggs from nine females fertilized by two males. The eggs were collected within 2.5h post-ovulation and stored in ovarian fluid at 15°C (150-g portions); ploidy was analysed 2–3d post-hatching. In Experiment 1, eggs were fertilized within 20 min post-collection (0h) and after 8h using spermatozoa:egg ratios of 10⁵ and 10⁶ and an egg:water ratio of 1:4 (=4 variants). In experiment 2, two fertilization environments, 10⁵/1:4 and 10⁴/1:15, were applied to eggs stored for 0h, 3h, 6h and 12h (=10 variants). In vitro egg ageing for 8/12h affected the incidence of ploidy abnormalities (autotriploids and haplo-diploid mosaics) in 33% of females (6/18) and in some cases reduced progeny yields. Egg ageing up to 6h had a negligible effect on ploidy abnormalities, hatching and malformations in all but two females that had considerably prolonged latency. Increasing spermatozoa:egg ratio from 10⁵ to 10⁶ did not impact fertilization rate but it reduced hatching and elevated occurrence of haplo-diploid mosaicism in 44% of females (4/9). A spermatozoa:egg ratio of 10⁴ was insufficient for adequate fertilization and never produced significantly fewer abnormal individuals than 10⁵. We conclude that storing regularly collected sterlet eggs up to 6h at 15°C and fertilization using 10⁵ spermatozoa:egg and 1:4 egg:water ratio will ensure low incidence of ploidy abnormalities and high progeny yields, and that late-ovulating females should be used with caution.       
 

Artificial reproduction,ploidy abnormalities,second polar body retention,polyspermy,spermatoza:egg ratio