The vent crab (Xenograpsus testudinatus), a dominant species in shallow water hydrothermal vents of Kueishan Island (Taiwan) and the Northwest Pacific fire ring, exhibits no significant genetic differentiation among populations. The underlying physiological traits and behavioral adaptations facilitating its survival in these environments are yet to be elucidated. This study collected X. testudinatus from two physicochemically contrasting sites: Kueishan Island and Shōwa Iōjima (Japan), the latter characterized by higher CO2 levels but lacking sulfides. Hemolymph analysis revealed comparable glucose levels between populations, but higher lactate in Shōwa Iōjima crabs, suggesting elevated CO2 contributes to anaerobic metabolism. In Kueishan Island, hemolymphic lactate positively correlated with sulfide presence and negatively with alkalinity, indicating a significant association between sulfide concentrations, alkaline components, and the regulation of anaerobic metabolic processes in the organism. Re-acclimatization experiments demonstrated a rapid lactate increase upon sulfide reintroduction, suggesting the importance of anaerobic respiration in adaptation. Moreover, vent crabs exhibited no positive sulfide chemotaxis, with Kueishan Island crabs displaying negative chemotaxis, potentially avoiding highly toxic areas. This study reveals diverse metabolic traits and behavioral responses employed by X. testudinatus to thrive in distinct hydrothermal habitats, underscoring the importance of phenotypic plasticity in their success.