In fish, due to the influence of the water temperature experienced before and after hatching, the sex may change to a sex different from the genetic sex determined at the time of fertilization.The research team at Tokyokaiyo University has succeeded in proving this "sex change phenomenon due to environmental water temperature" for the first time in a wild environment.
In this study, it was clarified that in the ginseng eagle that inhabits Tokyo Bay, the genetic female is transsexualized to a male with testes under the influence of high water temperature.The sex of an organism is generally genetically determined by the combination of sex chromosomes at the time of fertilization, but the sex of fish is easily affected by the habitat, and when exposed to high water temperatures before and after hatching, transsexual individuals appear. I have something to do.In recent years, there have been concerns about the rise in water temperature due to global warming on a global scale, and there has been concern that significant disturbance of the male-female ratio may occur in such species whose sex determination is susceptible to water temperature.However, the transsexual phenomenon has been reported only in the breeding environment and has not been proved in the wild environment.
This time, as a result of capturing wild ginseng eagle born from 2014 to 2016 and investigating males and females, it was found that the proportion of males is increasing year by year.And when we investigated the genotype of all individuals, the proportion of individuals who were genetically female but had sex reversal to males with testes increased year by year, especially in 2016. it was high.
Therefore, the hatching date of each individual was estimated using the analysis of the otolith ring pattern of fish, and the seawater temperature around the time of sexual differentiation was investigated.As a result, it was found that the 2016 population had a later spawning season than usual and experienced higher water temperatures than the 2014-2015 population.The relationship between the increase in the frequency of male sex reversal and high water temperature is statistically significant, demonstrating a causal relationship between sex reversal and empirical water temperature in Tokyo Bay.
In the future, it is expected that the effects of global warming on the sex of wild fish populations can be evaluated and predicted by using fish with high sexual temperature sensitivity as indicator species.
