Physiological basis for sterilizing effects of constant light in Lymantria dispar

ABSTRACT Females of gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae), mated to males kept in constant light (LL) as pharate adults fail to oviposit. In males, a rhythm of sperm release from the testis that occurs in light-dark (LD) cycles is abolished in LL, and the total amount of sperm released from the testis is approximately half of that of LD males. Moreover, any sperm that may be released from the testis of LL males tend to remain in the vasa deferentia instead of moving into the duplex as in LD males. Consequently, in LL very few sperm bundles are transferred to the bursa copulatrix during mating; furthermore, these bundles fail to disperse into spermatozoa and sperm do not reach the spermatheca. The presence of a spermatheca filled with sperm must play an important role in controlling oviposition because their removal from mated females prevents egg-laying. Our results indicate that the rhythm of sperm release from the testis is essential for the ability of sperm to migrate in male and female reproductive tracts. The rhythms may help to synchronize final stages of sperm development with the activity of phagocytic and secretory cells lining the reproductive tract.