Artificial insemination using trypsin-treated sperm in the silkworm, Bombyx mori

A new method was developed for artificial insemination of the silkworm. Virgin females artificially inseminated by this method oviposited fertilized eggs at a rate almost similar to that of females mated with males. Using inactive sperm collected from the seminal vesicles, we confirmed the previous finding by Omura, S., 1936a, Artificial insemination of Bombyx mori, Journal of Faculty of Agriculture, Hokkaido Imperial University 38, 135-150, and Omura, S., 1938, Studies of the reproductive system of the male of Bombyx mori II, Post-testicular organs and post-testicular behaviour of the spermatozoa, Journal of Faculty of Agriculture, Hokkaido Imperial University 40, 129-170, that the sperm of B. mori requires the secretion of the glandula prostatica for activation. Sperm also could be activated by trypsin. At an optimal concentration, 0.3 &mgr;g trypsin/ml in 50% semen solution, the fertilization rate as well as the number of eggs oviposited was almost equivalent to that obtained in normally mated moths. These results may contribute not only to basic studies on fertilization and reproduction in Lepidoptera but also to the development of long-term preservation of genetic resources by using cryopreserved sperm of B. mori and other Lepidoptera insects.