Aquaculture Reports (Jul 2020)
Standardization of egg activation and fertilization in sterlet (Acipenser ruthenus)
Abstract
This study was conducted to determine the minimum number of spermatozoa and optimal volume of activation water for effective fertilization of sterlet Acipenser ruthenus eggs. It was also to determine the minimum concentration of spermatozoa per ml of activation water during artificial propagation, when sperm with good motility and velocity (95 % motility and 150 μm s−1 curvilinear velocity) were used for fertilization. In three experiments, eggs (∼50) from three sterlet were fertilized by pooled sperm from four males in four replicates and incubated at 17 °C. The success of fertilization was evaluated at neurulation and hatching. Sterlet eggs were fertilized in proportion to the concentration of spermatozoa per ml in activation water. A total of 50,000 spermatozoa in 8 ml or 32 ml of activation water (concentrations of 6,250 and 1,563 spermatozoa per ml of activation water, respectively) was sufficient for successful fertilization based on neurulation and hatching rates. Neurulation and hatching gradually decreased with a decrease of the spermatozoa ÷ egg ratio from 6,250 to 114. A ratio 1÷4 between eggs and water was insufficient to provide adequate fertilization. Highest neurulation and hatching ratios were reported when the egg ÷ water ratio reached 1÷15, which is recommended for practical usage. Our results therefore showed that a very low concentration of 100 – 1,300 spermatozoa per ml with around 95 % motility and curvilinear velocity over 150 μm s−1 in activation water can provide effective fertilization. In studies of fishes with external fertilization, the volume of activation water during fertilization, total number of spermatozoa and eggs and/or concentration of sperm in activation water should be defined.
