Study On The Sex Difference Of Spectral Preference And Its Physiological Mechanism In Acrossocheilus Fasciatus

Light is an important ecological factor affecting the growth,development,reproduction and behavior in animals.Fish living in different environments have great differences in the spectral composition of their visual receptors for a long time.After adaptation and evolution,they show different sensitivity to different bands of spectrum and show different preference in behavior.At present,many scholars have studied the spectral preference of fish,but most of them have not considered the gender differences of fish.The development of fish is regulated by the aromatase and sex hormones,so there are great differences in organ structure,neuroendocrine system,physiological response and behaviors between male and female.Aromatase is the key enzyme to catalyze the conversion of androgens into estrogens.Therefore,this study aims to explore the following questions: whether there are gender differences in fish’s preference for specific light colors,and whether the biological basis of these differences is related to the activity of aromatase and the level of sex hormone?In this study,Acrossocheilus fasciatus was used as the research object.We first explored the differences of light preference between female and male.The colors of lights were red(at around 637 nm of wavelength),yellow(590 nm),green(518 nm),blue(465 nm),purple(405 nm)and white(447nm).Then we studied the possible regulatory effects of aromatase and estradiol on spectral preference by reducing estradiol secretion by aromatase inhibitors.We also studied the changes of sex hormone levels,aromatase activity and aromatase genes(cyp19a1a and cyp19a1b)expression under different light colors.The main results are as follows:(1)The residence time of female fish in red light area was significantly longer than that in other light color areas(p<0.05),and that of male fish in yellow light area was significantly longer than that in purple light area(p<0.05).It can be concluded that there was a significant sex difference in spectral preference in Acrossocheilus fasciatus: female preferred red light,male preferred yellow light.(2)When the activity of aromatase was inhibited and the concentration of estradiol decreased,the spectral preference of female and male changed: the female changes from red light to blue light,and male changes from yellow light to red light;when the concentration of estradiol increase,the spectral preference of female and male recovered.It can be concluded that the spectral preference of fish was related to the aromatase activity and the estradiol concentration,and the effect of aromatase activity on spectral preference is realized by changing estradiol concentration.Therefore,the sex difference in the color preference of lighting in the fish is most likely related to the sex difference in aromatase activity and estradiol levels.(3)There were significant differences in the concentration of estradiol and testosterone in plasma,the activity of aromatase in brain and related gene expression in male and female fish under different light colors(p<0.05).It can be concluded that light color can affect the expression of aromatase gene in the brain,and then change the aromatase activity in brain and the sex hormone concentration in plasma.In conclusion,light colors can change the expression of aromatase gene in the brain,and then change the aromatase activity in the brain,thus changing the concentration of estradiol.And the change of estradiol concentration can affect the spectral preference behavior in the fish.In the above mechanism,the sex difference in aromatase activity and estradiol levels results in the sex difference of spectral preference in the fish.