Effects of UVA radiation on cuticle microstructure of Tribolium castaneum

Ultraviolet A（ UVA） is a very important abiotic environmental factor to organisms. Cuticles are always the first line of defense to UV radiation. Changes of cuticle morphology and physiology contributing to UV resistance have been found in many marine organisms，higher plants，and human. But there were few researches about the cuticle of insects influenced by UVA. In this study，we used SEM and TEM to analyze changes of ultrastructural structure of larvae of Tribolium castaneum after 2 h and 4 h of UVA exposure. It was found that with the irradiation time increasing，boundaries of scale corresponding to the underlying epidermal cells on the dorsal surface of larvae were blurred and more secretions were deposited up to epidermal cells. In addition，the exocuticle became much thicker，and electron dense outside region of the exocuticle enlarged. However，endocuticle nuclei，Golgi apparatus and mitochondria were not influenced by UVA. These results might indicate that T. castaneum could change cuticle properties to reduce UVA damages.