Studies on Ultraviolet Sensitivity in the Silkworm, with Special Reference to the Effect of UV-irradiation on Melanin Formation in the Cuticle of the Striped Silkworm

Abstract

The purpose of this study was to clarify the change in ultraviolet sensitivity to inhibition of melanin formation in the cuticle during an instar. Striped silkworms were exposed to ultraviolet light at various stages of the third instar. By exposure to ultraviolet light at the third instar, a marked inhibition of melanin formation occurred in the later instars. The inhibition of melanin formation was the strongest when larvae were exposed to ultraviolet light at about 70 percent of the age of the instar. Tyrosinase activity in the epidermis was also decreased by UV-irradiation. Furtheremore, it was proved that deleterious effects of ultraviolet light on both inhibition of melanin formation and decrease of tyrosinase activity were partially photoreactivable. Possible relations between inhibition of melanin formation and decrease of tyrosinase activity were discussed.