Developmental Plasticity in Zebrafish (Danio Rerio): Effects of Early Life Exposure to a Stressor

Abstract

Experience of stress and/or cortisol, the end-product of activation of the hypothalamic-pituitary-interrenal (HPI) axis, may serve as a cue to trigger developmental plasticity. In fish, most research in this area has focused on effects of maternal stress or maternal cortisol levels on development, particularly with respect to the HPI axis and stress responses, and little attention has been paid to the effects of an endogenous stress response during early life. In the current study, zebrafish (Danio rerio) at four developmental stages (4, 7, 15 or 35 days post fertilization, dpf) were subjected to an air exposure stressor twice a day for two days. Individuals stressed early in life exhibited decreased survival and growth, increased whole-body Na+ and Ca2+ concentrations, and altered HPI axis activity associated with changes in anxiety-related behaviour at 7 to 35 dpf, with most effects diminishing with increasing age. Stress at 7 dpf was particularly effective at eliciting phenotypic changes, suggesting this age represents a critical window for cortisol to influence development. Finally, stress at 35 dpf induced masculinization, suggesting that cortisol influences sexual differentiation in zebrafish. These findings demonstrate that early-life stress in zebrafish triggers developmental plasticity, with effects on physiology and behaviour mediated by the HPI axis in an age-dependent manner.