Influence of Storage Duration of Ovulated Eggs Prior to Fertilisation on the Early Ontogenesis of Sterlet ( Acipenser ruthenus ) and Siberian Sturgeon ( Acipenser baeri )

The influence of short-term storage (0, 2, 4, 6, 9 and 12 h) in coelomic fluid at 15 °C of ovulated eggs of mature females from sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri) was studied. The percentage of fertilization, embryonic survival, abnormally developing embryos, hatching and larvae with malformations at hatching was measured. The results showed that ovulated eggs from A. ruthenus retained their fertilizability during 2–4 hours after ovulation depending on the maternal origin (83.5–43.7%; P < 0.05). The fertilization rate of batches of Siberian sturgeon eggs ranged from 55.7 to 21.9% at ovulation time. Between 4 and 6 hours after ovulation, the percentage of fertilized eggs and surviving embryos of A. baeri significantly decreased (P < 0.05). Ovulated eggs inseminated after 12 hours of storage in coelomic fluid at 15 °C showed a considerable reduction of their fertilizability that ranged from 61–35% in A. ruthenus and from 44–25% in A. baeri. Reductions in the embryonic survival rates were also observed: the decrease ranged from 58 to 38% in sterlet, and from 45 to 11% in Siberian sturgeon, recpectively. Hatching rates were also affected by the insemination time, egg batches presenting the highest values were those inseminated between 0–2 and 0–4 hours after ovulation in A. ruthenus (28.6–64.9%) and A. baeri (16.7–26.3%), respectively. At hatching, the lowest rates of malformed larvae with 5.6–11.4% in both species were mainly observed amongst those larvae obtained from egg batches inseminated between 0–4 and 0–6 hours after ovulation, respectively. No significant differences were found between larvae obtained from egg batches of A. ruthenus and A. baeri inseminated at different times (P > 0.05). The results showed that ovulated eggs of A. ruthenus and A. baeri stored in coelomic fluid at 15 °C lost their fertilizability and viability, and became over-ripe between 2–4 and 6 hours after ovulation, respectively.