Rhythm Of Sperm Release Research Articles

Clock-controlled rhythm of ecdysteroid levels in the haemolymph and testes, and its relation to sperm release in the Egyptian cotton leafworm, Spodoptera littoralis

In Spodoptera littoralis, testicular sperm release occurs in a daily rhythm, which is controlled by endogenous circadian oscillator located in the male reproductive system. Although this rhythm is essential for male fertility, factors that initiate and maintain daily sperm release are not understood. In this study, we investigated a modulatory role for ecdysteroids in the sperm release rhythm and identified the source of ecdysteroids in adult males. We found that the onset of sperm release occurs two days pre-eclosion and coincides with a significant decrease in haemolymph ecdysteroids levels. 20-HE injection into the pupae prior to the first sperm release delayed its initiation and disrupted the developing rhythm in a dose dependent manner. 20-HE injection into adults depressed the number of sperm bundles leaving the testes. A day before the initial sperm release, ecdysteroid levels in the haemolymph and testes begin to oscillate in a circadian fashion. Ecdysteroid rhythms continue throughout imaginal life and correlate with the rhythm of sperm release. In each cycle, testicular sperm release coincides with a trough in testicular ecdysteroid concentration. Rhythmic changes in ecdysteroid levels are regulated by an endogenous circadian oscillator that continues to function in decapitated males. The generation of a complete cycle of ecdysteroid release by testes cultured in vitro indicates that this oscillator is located in the gonads. The haemolymph ecdysteroid levels are significantly lower and arrhythmic in males with removed testes, indicating that the testes are an important ecdysteroid source that may contribute to oscillations in haemolymph ecdysteroid levels.

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.

Role of ecdysteroids in the regulation of sperm release from the testis of the gypsy moth, Lymantria dispar

Release of mature sperm from the testes of the gypsy moth, Lymantria dispar, into the seminal ducts occurs in a daily rhythmic pattern. The rhythm of sperm release is initiated in developing pharate adults 3–4 days after spermatogenesis and development of the reproductive tract has been completed. At that time a significant decline occurs in the blood titre of RIA-detectable ecdysteroids. Infusion of 20-hydroxyecdysone into male pupae inhibits the release of sperm from the testis in a dose-dependent and age-dependent fashion. The decline in haemolymph ecdysteroid levels seems essential for the initiation of the rhythmic release of sperm from the testis, but does not appear to play a role in determining the phase of this rhythm.

Circadian System Controlling Release of Sperm in the Insect Testes

Release of mature sperm from the testis into seminal ducts of the gypsy moth exhibits a circadian rhythm. The rhythm of sperm release was shown to persist in vitro, in isolated complexes of testis and seminal ducts cultured in light-dark cycles or in constant darkness. The phase of the rhythm was also reset in vitro by exposure to shifted light-dark cycles. Therefore, the testis-seminal ducts complex from the gypsy moth is photosensitive and contains a circadian pacemaker, which controls the rhythm of sperm movement. This finding extends the range of structures in multicellular organisms that are known to contain circadian oscillators and provides a new model system in which circadian mechanisms may be studied.