Ontogeny of the cortisol stress response in larval rainbow trout.
The ontogeny of the interrenal stress response in rainbow trout was characterized by measuring resting and acute-stress-induced changes in whole-body cortisol levels in embryos and larvae at different early developmental stages. In Experiment 1, resting cortisol levels averaged 6.0 ng/g in newly fertilized eggs, fell to less than 0.3 ng/g by the time of hatching at Week 4 (incubation at 10 degrees), and increased to 1.4 ng/g by Week 5. Cortisol levels did not change in response to acute stress in 3-, 4-, or 5-week-old fish. In Experiment 2, resting cortisol averaged 1.4 ng/g in newly fertilized eggs, fell to less than 0.03 ng/g by Week 2, and then steadily increased between Weeks 3 and 6 to a peak of 4.8 ng/g before falling to 1.2 ng/g by Week 7. Cortisol levels did not change in response to acute stress in 3-, 4-, or 5-week-old fish. Six-week-old fish showed a 2.3-fold increase in cortisol levels at 1 hr poststress, indicating that the hypothalamic-pituitary-interrenal axis first develops responsiveness to stress 2 weeks after hatching and 1 week before the onset of exogenous feeding. The stress hyporesponsive period after hatching in rainbow trout may be homologous to the 2-week stress hyporesponsive period after birth in rodents, the function of which may be to maintain low, constant corticosteroid levels during a critical developmental period when these steroids can have permanent effects on neural organization. As suggested for mammals, this period may be a time when rainbow trout are particularly vulnerable to environmental effects on their subsequent development.
Barry
T P
TP
University of Wisconsin Aquaculture Program, Department of Food Science, Madison 53706.
Malison
J A
JA
Held
J A
JA
Parrish
J J
JJ
D000375:Aging; D000818:Animals; D015536:Down-Regulation; D005393:Fish Diseases / Q000378:metabolism; D006854:Hydrocortisone / Q000378:metabolism*; D007031:Hypothalamus / Q000502:physiology; D007401:Interrenal Gland / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D017686:Oncorhynchus mykiss / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D010902:Pituitary Gland / Q000502:physiology; D013312:Stress, Physiological / Q000378:metabolism / Q000662:veterinary; D015053:Zygote / Q000378:metabolism
D006854:Hydrocortisone