Tissue and Sex-Specific Transcriptomic Signatures Underlying Aggression behavior of Chinese Mitten Crab (Eriocheir sinensis).

Aggressive behavior is a critical constraint on sustainable crustacean aquaculture, causing cannibalism and yield loss. However, in the economically important Chinese mitten crab (Eriocheir sinensis), the molecular mechanisms underlying aggression responsiveness, particularly sex-specific regulation, remain poorly understood. Here, we used a standardized behavioral assay to quantify reactive aggression across three developmental stages and classified the quantified crabs into high-, moderate-, and low-aggression groups. Biochemical and transcriptomic profiling of the thoracic ganglion and the first pereiopod muscle were investigated to decode the mechanisms of aggression. High aggression was associated with significantly elevated catalase (CAT) activity and malondialdehyde (MDA) content, indicating increased oxidative stress that may reflect both the energetic demand of aggressive responses and the acute stress induced by the assay. Transcriptomic analyses showed that the upregulated genes in high-aggression crabs were enriched in neurotransmission and signal transduction pathways including dopaminergic, GABAergic, serotonergic, cAMP, and calcium signaling, which are consistent with altered neuromodulatory and signal-transduction capacity associated with high reactive aggression. Notably, significant enrichment of these neurotransmitter-related pathways was observed only in males, suggesting distinct sex-dependent adaptive strategies for aggressive behavior. Moreover, upregulated genes identified in the first pereiopod muscle of both females and males were mainly involved in metabolic processes, signal transduction, and immune defense pathways, indicating conserved functional roles across sexes. This study provides an integrative neurophysiological and transcriptomic framework for understanding the stimulus-induced aggressive response in Chinese mitten crab, highlighting oxidative trade-offs, tissue-specific regulation, and sex-dependent molecular strategies. These would help to conduct selective breeding and behavioral control in crustacean aquaculture.