Environmental Complexity During Early Life Stage Affects Mosquitofish Personality

Personality refers to the existence of significant differences and stability in behavioral strategies among different individuals of animals within the same species or even within the same population.Over the past few decades,individuality has been discovered in some animal groups.In recent years,the study of animal personality has become a hotspot in behavioral ecology,mainly focusing on: 1)the reasons for the evolution of animal personality;2)ecological significance of animal personality.At present,accepted measures of animal personality traits include: bravery/shyness,exploration,activity,aggression and sociality.Many factors can influence an animal's personality,wherein internal factors include body size,sex,metabolic status and so on,and external factors include environment,temperature,food availability and so on.The growth environment of an animal,especially the early growth environment,has an important influence on personality.The object of this study is mosquitofish,which has advantages of wide distribution,easy fishing,obvious sex characteristics,easy behavior observation and data collection,etc.,and has become an ideal experimental research model.Based on the previous studies of mosquitofish,this topic is performed by raising larvae of mosquitofish at three different levels of complexity in early growth environment.After the larvae reached sexual maturity,samples from each environmental gradient were taken for three personality behavior experiments mosquitofish namely shy experiment,exploratory experiment and sociality experiment.In this study,the length of time spent by individual mosquitofish coming out from the shelter was taken as the basis to determine extent of shyness,and the movement track length of individual mosquitofish in the exploration area was taken as the standard to measure exploratory strength,and the social size was analyzed by the length of stay time for experimental mosquitofish close to non-experimental mosquitofish.In this article,complexity of aquatic plants set in early growth environment of mosquitofish was taken as the independent variables,combining with gender differences,to fit univariate linear mixed effects models to test the influence of environmental complexity and gender factors on population average behavior,and fitting of multivariate model was used to quantify repeatability of behavior(i.e.,personality)and the correlation between behavior(i.e.,behavioral syndrome).This study solved the key scientific problems of the mechanism of the complexity of early growth environment on animal personality,analyzed the reasons for the formation of mosquitofish personality,and clarified the significance of mosquitofish personality in evolution and ecology.This experiment provides a scientific basis for the study of animal behavioral ecology.The results of this studyshowed that in the three growth environments with different levels of complexity,open A,medium B and complex C,the body length of female mosquitofish was greater than that of male fish,and the individual mosquitofish raised in the open environment was more brave,because they spent less time out from the shelter.To compare exploratory data of male and female mosquitofish in three growth environments at different levels of complexity,on average,the exploratory distance of male mosquitofish is greater than that of female fish,so male mosquitofish is more exploratory than female fish.In terms of sociability,females spent more time in social areas than that of males,and this social tendency was consistent across three habitats.Overall,female mosquitofish are more shy and social than males,and those raised in the complex environment are more shy,less exploratory,and more social than those raised in the open environment.In all personality tests,there were always large differences in individual mosquitofish behavior,suggesting differences in personality between males and females raised in different environments.Consistent behavioral differences were also found in three personality traits of female and male mosquitofish.At the same time,95% confidence intervals for repeatability of three personality traits of mosquitofish were all overlapped,and the repeatability values had no difference,indicating that gender or complexity of early growth environment had no significant influence on behavioral repeatability.This study also found that mosquitofish reared in all habitats showed negative correlation between shyness and exploration behavior at individual phenotype and individual level,indicating that these two personality traits constituted a strong shyness and exploration behavior syndrome.The experimental results showed that there was a negative correlation between shyness and exploratory behavior of male mosquitofish in medium environment and a positive correlation between exploratory behavior and social behavior of male mosquitofish in medium and complex environments.This study provides strong evidence that adult average behavior of mosquitofish will change as they grow and develop in different habitats with different levels of complexity during their infancy that is,the complexity of the growth environment in the early stage plays an important role in the development of animal personality.