What Forms, Maintains, and Changes the Boldness of Swimming Crabs (Portunus trituberculatus)?

SIMPLE SUMMARY: The formation and maintenance mechanism of personality is a hot topic in personality research. The boldness of the swimming crab (Portunus trituberculatus) has the greatest influence on its behavior, but the physiological factors leading to the stability of and difference in boldness are not yet clear. In this study, the factors affecting the formation and maintenance of and change in the boldness of swimming crabs are investigated from the perspectives of behavior, physiology, and neurotransmitters. The results show that the differences in boldness among crabs remain consistent for a long time and are closely related to the body’s energy and neurotransmitter metabolism. ABSTRACT: Boldness of personality is an important theme in animal behavior and has significant ecological and evolutionary consequences. Studies on boldness in crustaceans typically focus on their behavior, while relatively few studies have focused on the formation and maintenance of and change in boldness, such as energy metabolism and neurotransmission. In this study, we measured the boldness of swimming crabs (Portunus trituberculatus) and analyzed the relationship between boldness and oxygen consumption rate, energy concentration, and the relative expression of energy-metabolism-related and 5-HT genes in mRNA. The results showed that boldness remained stable across repeated tests but changed under dangerous conditions. Swimming crabs could be divided into bold and shy individuals. Bold individuals consumed oxygen at a significantly higher rate than shy individuals. Lactate and glucose concentrations in hemolymph were significantly lower in bold individuals than in shy individuals, and mRNA relative expression of Na(+)/K(+)-ATPase and 5-HT genes was significantly higher in bold than in shy individuals. Preliminary results indicate that energy metabolism and neurotransmitters may underlie the formation and maintenance of personality characteristics of swimming crabs. Swimming crabs also exhibit behavioral flexibility in order to cope with risks. This may be an adaptation to their complex environments.