Effect of constant light on male sterility in the cotton leafworm Spodoptera littoralis

• Published in: Physiological entomology Vol. 24; no. 2; pp. 165 - 170
• Main Authors: Bębas, P., Cymborowski, B.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.06.1999; Wiley Subscription Services, Inc
• Subjects: Cotton leafworm; eupyrene sperm; light effect; male sterility; Noctuidae; spermatogenesis; Spodoptera littoralis; testes
• ISSN: 0307-6962; 1365-3032
• DOI: 10.1046/j.1365-3032.1999.00127.x

Summary Females of the cotton leafworm (Spodoptera littoralis) reared in long day conditions (LD 16:8 h) and mated to males kept throughout the whole period of development in continuous light (LL) oviposit very small numbers of mostly sterile eggs. It was found that in control males reared from the first larval instar in long day conditions there was a large accumulation of euperene sperm bundles in their testes on day 1 after imaginal moult. On day 10 of adult life the number of the sperm bundles was very small. In males kept from the first instar in continuous light there was also high number of sperm bundles on day 1 after imaginal moult but it did not decrease significantly on day 10 as was observed in controls. Transfer of different developmental stages of S. littoralis from long day conditions to continuous light resulted in a big difference in the density of eupyrene sperm bundles in their testes. In control insects reared through the whole of their development in long day conditions there was a significant decrease in the density of eupyrene sperm bundles on day 10 of adult life. By contrast, in males in continuous light, regardless of their developmental stage when transferred, there was either no change in density of sperm bundles in day 10 adults or there was a significant increase in comparison with day 1 adults. The highest density of eupyrene sperm bundles was observed in day 10 adults when they were transferred to continuous light shortly before moulting to the last instar (as day 4 larvae in the last stadium or day 1 pupae). Generally, the density of eupyrene sperm bundles on day 10 of adult development was about 2–2.5 times higher in males in continuous light then those under long day conditions. The results presented here indicate that the last larval instar and the pupa are the stages most sensitive to constant light treatment, which greatly reduces the amount of eupyrene sperm bundles released from the testes.