Fertility restoration of cryopreserved semen by hyper ratio of apyrene sperm in Bombyx mori

Abstract

Feasible methods for sperm cryopreservation and subsequent artificial insemination are urgently needed to maintain silkworm genetic resources with less laborious work and space cost. We have discovered that loss of the fertilizing ability of cryopreserved diploid (p50) semen was restored by the addition of either fresh or frozen apyrene sperm from triploid donors. To decrease usage of the amount of stored diploid semen, we monitored the effective ratio of cryopreserved p50 semen and apyrene sperm from triploid males to restore fecundity. Restoration of the fertilizing ability of cryopreserved p50 semen was kept by roughly one fourth decrease of the amount by increasing the apyrene sperm ratio. Because semen collection from diploid males requires skillful and careful techniques, decreasing the amount of cryopreserved semen may practically save laborious work. It may also contribute to successful restoration of fertilization with a small amount of semen from a small number of individuals.