Testing cryopreserved European eel sperm for hybridization (A. japonica × A. anguilla).

The objective of this study was to assess impact of cryopreserved European eel sperm and Japanese eel native sperm on early fertilization, hatch, survival, and malformation rates of larvae, as well as develop molecular techniques to distinguish different eel species. Eggs from Japanese eel females (Anguilla japonica) were artificially fertilized with sperm of Japanese eel males and cryopreserved sperm from European eel (A. anguilla, extender was modified Tanaka solution and methanol as cryoprotectant). There were no statistical differences (p > 0.05) among the measured parameters such as fertilization, hatch and survival after 10 days post-hatch rates due to large individual differences. The malformation rate of larvae compared to the hatching rate was higher in cryopreserved groups than in the control indicating that the methodology needs further refinement. Genetic analyses (PCR-RFLP, PCR-HRM) proved a clear result in the detection of paternal contribution in hybridization between the Japanese and the European eel and applied PCR-HRM method is a quick and cost effective tool to identify illegally imported A. anguilla at the glass eel stage, which can be transported from Europe to Asia.