Host: The Japanese Society of Toxicology
Daphnia magna has long been used to assess toxicity in environmental waters. However, there have been limited approaches to study the mechanisms how the chemicals affect Daphnia magna and cause adverse effect. In particular, it has been difficult to distinguish between general toxicity and endocrine disruption because changes in the molting interval, which is an indicator of the adverse effect of crustaceans, are not only observed in exposure to endocrine disrupting chemicals with activity such as molting hormone and juvenile hormone, but also in general toxic effects.
To distiquish these adverse effects, we have developed a system to detect hormonal activities by the use of Daphnia manga. A reporter gene under the control of the molting hormone receptor or the juvenile hormone receptor was introduced into Daphnia genome by the genome editing technique. These genome-edited Daphnia magna not only responded to endogenous hormones, but also to chemical substances with hormone-like activity in environmental water and emitted fluorescence, indicating the possibility of using them for monitoring environmental water.
It has been known that Daphnia magna exposed to juvenile hormone-like chemicals at a specific period produce males. In this study, we also found that the number of offspring was decreased when Daphnia is exposed to juvenile hormone-like chemicals. This finding suggests that the juvenile hormone regulates the population size, which is a new aspect of reproductive toxicity and may lead to the elucidation of the toxicological mechanism of hormone-like chemicals.
