Artificial Fertilization Using Testicular Spermatozoa in the Japanese Eel Anguilla japonica

Abstract

The motility and fertility of the Japanese eel testicular spermatozoa, which had acquired motility during an incubation with K30 solution (consisting of 30 mM KCl, 134.5 mM NaCl, 1.3 mM CaCl2, 1.6 mM MgCl2, 20 mM NaHCO3, and buffered with 20 mM TAPS-NaOH at pH 8.1), were compared with those of the milt spermatozoa obtained from the genital pore of a Japanese eel. The motility percentages of milt spermatozoa and testicular milt spermatozoa, were 84.7 ± 4.1% and 2.6 ± 1.9%, respectively. The percent motility of incubated testicular milt spermatozoa was 63.3 ± 2.2%. The fertility and hatchability of the milt and incubated testicular milt were significantly higher than those of testicular milt. There were no significant differences found between the fertility and hatchability of the milt and those of the incubated testicular milt. To examine the toxicity of the high potassium concentration in the K30 solution on egg fertility, we compared the fertility and hatchability of milt spermatozoa diluted with K30 solution or K15 solution. No significant differences in the fertility or hatchability were found between the K30 and the K15 solutions. These results indicate that the testicular spermatozoa which acquired motility during their incubation in K30 solution are just as fertile as the motile milt spermatozoa, and that K30 solution is suitable as a milt diluent in the artificial fertilization of the eel.