The individuality affects the hormone secretion of the caudal neurosecretory system (CNSS) and correlation with respiratory metabolism, spontaneous activity and appetite in olive flounder (Paralichthys olivaceus)

Abstract

In farmed animals, individuality have demonstrated links to performance traits, health and disease susceptibility, and animal welfare. This research aims at exploring whether there are differences in the secretion of hormones in the caudal neurosecretory system of different individuailty, and investigating whether it is related to physiological behaviors. In the experiment we selected through multiple behavioral tests two types of olive flounders, bold individuals (BI) and shy individuals (SI), and found that they differed in behavior and physiology. The standard metabolic rate, maximum metabolic rate, and absolute aerobic scope of BI were markedly higher than those of SI. Additionally, the swimming speed of BI was also higher than that of SI in the natural photoperiod. BI and SI showed distinct coping styles to deal with acute stress. Overall, the number of Dahlgren cells secreting UI, the relative UI and CRH mRNA expression in the caudal neurosecretory system (CNSS) of SI was relatively higher than that in BI. By contrast, the number of Dahlgren cells secreting UII and the mRNA expression of UII was lower than that of BI. Through the correlation analysis, it was found that there were some differences in hormone secretion among different individuality groups, which indicated individuality affected hormone production and the number of secretion cells and existed correlation with respiratory metabolism, spontaneous behavior, appetite. It means differences in the regulation mechanism of the flounders in BI and SI.