Effects of Yininemertes pratensis on Glass Eels from the Han River, Korea

Nemerteans (ribbon worms) mostly inhabit benthic habitats. The nemertean Yininemertes pratensis was recently reported to a negatively affect the glass eel net fishery in the Han River, Korea, but the causative mechanism has not yet been fully investigated. The present study was performed to investigate the mechanisms associated with the death of these eels by Y. pratensis. Our results showed that eel survival rates were not affected by exposure to a Y. pratensis polypeptide extract nor by coincubation with Y. pratensis in a sufficiently spacious environment. Yininemertes pratensis secretes tetrodotoxin and small molecular toxins under stressful conditions; therefore, co-incubated in a restricted spaced. Yininemertes pratensis decreased eel survival rate and accelerated eel death. In this study, we demonstrated that mucus secreted by Y. pratensis was associated with ell deaths.