Spider predatory aggressiveness exhibits diverse personality and plasticity associations and complex neurophysiological mechanisms.

Although personality has been popularly studied for decades, the relationship between plasticity and personality remains unclear, and the underlying neurophysiological mechanisms are still not well understood. Here, we addressed this gap by comprehensively integrating field surveys, behavioral tests, transcriptome, and biochemical analyses to study the personality and plasticity of predatory aggressiveness in the wolf spider, Hippasa holmerae. A total of 103 H. holmerae were collected from a field population and their willingness to attack a dangerous East Indian harvest ant prey (Carebara diversa) was each evaluated. We found that nearly half of the individuals exhibited high behavioral plasticity while the others exhibited apparent personality, and results of modeling approach suggests that proactive personality might indeed limit adaptive plasticity. The brains of individuals displaying apparent high or low aggressiveness were subjected to transcriptome analyses. The results showed that 19 physiological systems had more than 20% of their associated genes exhibiting differential expression patterns between the high and low aggressive groups. Furthermore, almost all of these differences were due to genes being significantly upregulated in highly aggressive individuals. Results of biochemical analyses further showed that the concentration of tryptophan in the brains of highly aggressive individuals was significantly lower than that of low aggressive ones. These gene expression and amine variation patterns were consistent with the characteristics of big and small engine individuals proposed by the pace of life syndrome theory and energy management models. Here, we show the personality-plasticity association within a population and empirically demonstrate that personality differences might be caused by the differences in multiple physiological systems. These results highlight the importance of distinguishing personality and plasticity in behavioral tests and the importance of comprehensively examining multiple systems while conducting personality mechanistic studies.