CHUANG, S.C.*; CHEN, J.H.; Institute of Zoology, National Taiwan University; Department of Life Science, National Taiwan University; Institute of Zoology, National Taiwan University; Department of Life Science, National Taiwan University: The study of crawling behavior, oxygen consumption and oxidative stress in earthworm Amynthas gracilis after UV-B exposure

After a heavy raining, it is possible to see earthworms wandering on the soil surface or dying in a small water pool at the next morning. Why do they not crawl back to soil? In this study, ultraviolet (UV) exposure was found to be correlated to the impact on earthworms. The damage of ultraviolet radiation on earthworm, Amynthas gracilis, could be distinguished into two responses. The acute response is that the appearance of strong muscle contraction such as irregular S-shape movement and jumping behavior under UV exposure. The phenomenon should be caused by abnormal muscle coordination. The chronic response after UV-B exposure showed the damage of skin and muscle cells as well as high mortality in 12 hours. In addition, the oxygen consumption of A. gracilis was significantly decreased after UV-B exposure. Because the circulation of earthworms is mediated by muscle contraction, the UV-exposed earthworms encountered stifle when their muscles didnít contract normally. In addition, the UV-B exposure caused A. gracilis epithelia serious necrosis that affected the oxygen diffusion into the blood vessel of the earthworms resulting short supply of oxygen. According the foregoing reasons, they would choke to die. Besides, we found that the product of lipid peroxidation (TBARS, thiobarbituric acid reactive substance) and H2O2 of earthworms were increased after UV-B expose. Meanwhile, the activity of antioxidant enzymes, such as catalase, GPx, and SOD, were decreased. It inferred that the epithelial necrosis and muscular damage were mediated by UV-induced oxidative stress. According this study, we infer earthworm A. gracilis would be a good animal model to study the stress of ultraviolet.