Differences in Agonistic Behavior and Energy Metabolism between Male and Female Swimming Crab Portunus trituberculatus Based on the Analysis of Boldness

Abstract

Individual differences in metabolism and agonistic behavior have been a key research area in evolution and ecology recently. In this study, we investigated the boldness of swimming crabs Portunus trituberculatus and explored the agonistic behavior between female and male crabs, specifically examining competitions between bold females vs. bold males (BF–BM), bold females vs. shy males (BF–SM), shy females vs. shy males (SF–SM), and shy females vs. bold males (SF_BM) and its relationship with energy metabolism. The main results revealed the following: There was no significant difference in boldness between females and males, while there were more bold individuals than shy in both females and males. Bold individuals initiated significantly more fights than shy individuals, and male initiators won significantly more fights than female initiators. The duration and intensity of fight between bold individuals was significantly higher than fights between shy individuals. For males, the concentration of glucose in the hemolymph was significantly higher in shy crabs than bold crabs, while there was no significant difference between shy and bold individuals in females. After fighting, the concentration of glycogen in claws was lower than that before fighting, and the concentrations of glucose and lactate in hemolymph were significantly higher after fighting than before. We found that the fighting willingness and ability were higher in male crabs than females and higher in bold crabs than shy. Fighting ability varied between sexes and was influenced by boldness and energy state.