The Study of Crawling Behavior, Oxygen Consumption and Oxygen Stress in Earthworm Amynthas gracilis after UV-B Exposure

Abstract

After a heavy raining day, it is possible to see earthworms wandering on the soil surface at the next day morning. They might die in few hours. Why did they not crawl back to soil but die in water? By using earthworms, Amynthas gracilis which presents the described behavior, ultraviolet (UV) was suspected as the main factor to kill the earthworms. The damage of ultraviolet radiation on earthworms could refer to two responses, acute response and chronic response. The acute response is that the appearance of strong muscle contraction such as abnormal S-shape movement and jumping behavior. The phenomenon might be caused by bad muscle coordination. The chronic response showed the damage of skin and muscle cells and high mortality after UV-B exposure. The oxygen consumption of A. gracilis was significantly decreased after UV-B exposure. Because the circulation of earthworms is mediated by muscle contraction, earthworms maybe stifle when their muscles didn't contract normally. Meanwhile, the chronic response, seriously A. gracilis cause epithelial necrosis that affect the oxygen diffused into the blood vessel of the earthworms. UV also increased oxidative stress on cells. I found that the lipid peroxidation, antioxidant enzyme (catalase, GPx, SOD) of earthworms was increased after UV-B expose. It inferred that oxygen stress was another reason that caused earthworms died after UV-B exposure.