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Glucocorticoid and behavioral variation in relation to carbon dioxide avoidance across two experiments in freshwater teleost fishes
- Tucker, Emily K., Suski, Cory D., Philipp, Madison A., Jeffrey, Jennifer D., Hasler, Caleb T.
- Biological invasions 2019 v.21 no.2 pp. 505-517
- Lepomis macrochirus, Micropterus salmoides, acid-base balance, avoidance behavior, carbon dioxide, carbon dioxide enrichment, cortisol, ecological invasion, fish, freshwater, intraspecific variation, invasive species, personality
- Organismal responses to stressors can be influenced by several internal and external factors including physiological condition and inherent behavioral type. Carbon dioxide (CO₂), a known stressor for fish, is naturally increasing in fresh water, and has been proposed as a non-physical barrier to prevent invasive fish movement. Intraspecific differences in how fish respond to CO₂ challenges have been noted, with some individuals responding at low partial pressures of CO₂ (pCO₂), and others responding at higher pCO₂. Sensitivity to pCO₂ may play a role in avoidance behaviors with respect to CO₂ barriers and may predict how fish respond to naturally occurring CO₂ challenges. We sought to determine the role that both physiological condition (i.e., elevated cortisol) and personality (i.e., boldness) play in influencing behavioral responses. To accomplish this goal, a shuttle box assay was used to determine the pCO₂ that elicited avoidance in cortisol-injected or non-injected largemouth bass (Micropterus salmoides), as well as bold or shy bluegill (Lepomis macrochirus). Cortisol-injected largemouth bass shuttled at 45% higher pCO₂ than control fish, but personality of bluegill had no effect on shuttling. It appears that an individual’s cortisol level can affect CO₂ avoidance, likely mediated through the effects of cortisol on acid–base balance at the gill, or through the effects of cortisol on coping styles. Our finding has important implications for how fish respond to either natural or anthropogenically-driven changes in CO₂, as stressed fish with high cortisol would appear to be more tolerant of elevated CO₂, independent of personality type.