Submitted to: American Fisheries Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2014
Publication Date: 3/18/2014
Citation: Peterson, B.C., Small, B.C., Chatakondi, N.G. 2014. Ontogeny of the cortisol stress response in channel catfish (Ictalurus punctatus). American Fisheries Society Annual Meeting. P.46.
Technical Abstract: Cortisol is a glucocorticoid hormone which is an endocrine signaling molecule in all vertebrates and acts through intracellular glucocorticoid receptors (GR). Cortisol affects many biological functions including immunity, stress, growth, ion homeostasis, and reproduction. The objective of this study was to investigate the ontogeny of the cortisol stress response in channel catfish (Ictalurus punctatus) at several early life stages. Resting and stress-induced cortisol levels and two GR (GR-1 and GR-2) were measured. Resting cortisol levels in newly fertilized eggs averaged 2.4 ± 0.2 ng/egg and decreased to 0.4 ± .01 ng/egg by day 5. Cortisol levels in newly fertilized eggs subjected to an acute stress (lowered oxygen from 6 ppm to 2 ppm) averaged 2.3 ± 0.1 ng/egg and decreased to 0.3 ± .03 ng/egg by day 5. At hatching, resting cortisol levels were 2.4 ± 0.1 ng/0.1g tissue while levels increased to 8.3 ± 0.2 ng/0.1g tissue in fry subjected to an acute stress (P < 0.05). Four days post-hatch, resting cortisol levels were 8.3 ± 0.1 ng/0.1g tissue while levels increased to 14.9 ± 0.4 ng/0.1g tissue in fry subjected to an acute stress (P < 0.01). There was no significant difference between GR-1 and GR-2 mRNA in stressed and unstressed embryos. Four days post-hatch, GR-1 mRNA increased 2-fold while GR-2 mRNA increased 3-fold in fry that were subjected to low oxygen (P < 0.05). These results indicate that cortisol biosynthesis, integration and maturation of the hypothalamic-pituitary-interrenal (HPI) axis can be observed in channel catfish at hatching. Maternal cortisol may be responsible for levels of cortisol detected at fertilization and throughout embryonic development.