Feeding habit transition induced by social learning through CaMKII signaling in Chinese perch (Siniperca chuatsi)

Abstract

Social learning plays pivotal roles in gaining new foraging skills and food preferences. However, the molecular mechanism underlying the effects of social learning on feeding habits is unclear. Chinese perch, as a demersal piscivore, has a unique feeding habit. Once the fry of Chinese perch start feeding, they only accept live prey fish in the wild and refuse dead prey fish or artificial diets. In the present study, we used the inhibitor of the Ca2+/calmodulin-dependent protein kinase II (CaMKII) signaling pathway KN-93 in vivo and in vitro, to explore how social learning can affect the transition from live prey fish to dead prey fish in Chinese perch. Analysis of gene expression, protein phosphorylation, success rate, learning times, and food intake allowed us to gain insights into the molecular mechanism of social learning in acquiring new feeding habits in Chinese perch. Our results showed that the p-CaMKII, phospho-cAMP-response element binding (p-CREB) and proto-oncogenes c-fos (c-fos), and melanin-concentrating hormone (mch) expression levels were significantly lower with KN-93 treatment than levels in the control condition, whereas the expression of the anorexigenic gene proopiomelanocortin (pomc) was significantly higher in vitro. The increased success rate and food intake of Chinese perch induced by social learning, were diminished after the injection of the CaMKII inhibitor KN-93 in vivo. Inhibited signaling of CaMKII was observed in Chinese perch after KN-93 treatment. We also found that the expression levels of the c-fos, mch or pomc genes were increased or decreased in the learning group and then decreased or increased in the learning group with KN-93 injection, respectively. These results indicate that the higher expression of the orexigenic mch gene and the decreased expression of the anorexigenic pomc gene might contribute to the learning of eating dead fish prey in Chinese perch. Altogether, our results showed that social learning could promote the feeding habit transition from live prey fish to dead prey fish through the CaMKII - c-fos - pomc/mch signaling pathway in Chinese perch.