Stress Response and Acclimation in the Adult Turquoise Killifish Nothobranchius furzeri

The turquoise killifish Nothobranchius furzeri is an increasingly popular model species for comparative vertebrate research. As such, the basic physiology, including responses to one or multiple stress events are of primary interest to the present study. After successful rearing, adult male and female killifish were exposed to one or more acute confinement events. Whole-blood was taken from adult males, in addition to male and female whole-body samples for cortisol analysis. Separate adults were also sampled for tissue specific expression of corticotropin releasing hormone (CRH), mineralocorticoid receptor (MR), and glucocorticoid receptor (GR) mRNA within the cranium, gills, and liver. Following a 30 minute confinement stress, male plasma cortisol significantly differed from baseline at 30 minutes (P=0.04). Similarly, both male and female whole-body cortisol were significantly increased (P=0.004 and P=0.04, respectively) at 15 and 30 minutes post-stress. Whole-body cortisol did not differ between the sexes at any sampling point, however; expression of gill MR at 15 minutes was significantly higher in males (P=0.05). Exposure to daily repeated confinement affected the cortisol response in both males and females, resulting in lower baseline and 60 minutes post-stress values in repeatedly-stressed males (P=0.04 and P=0.006, respectively) and lower cortisol at 30 and 120 minutes post-stress in repeatedly-stressed females (P=0.04 and P=0.04). Repeated exposure also resulted in increased cranial CRH and MR at 15 minutes post-stress (P=0.02 and P=0.05, respectively) compared to singly-stressed males. In females, repeated exposure increased gill MR at 120 minutes (P=0.05), but a single stressor resulted in relatively greater expression of cranial CRH at 120 minutes (P=0.02) and MR at 15 minutes (P=0.05). Collectively, the reduced cortisol production observed in repeatedly-stressed adults coupled with only transient changes in receptor expression suggest acclimation to daily stressors can be detected in as little as one week in adult turquoise killifish. This is also the first description of the stress response on this important model species