Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 14, 2005
Publication Date: February 13, 2006
Citation: Small, B.C., Peterson, B.C., Murdock, C.A. 2006. Food deprivation and the catfish endocrine system. Aquaculture America Conference 2006. Las Vegas, NV. p. 293 and p. 17. Technical Abstract: Channel catfish (Ictalurus punctatus) are an economically important species in the United States. In culture, channel catfish are often subjected to periods of restricted feeding and food deprivation as management tools for water quality and disease. Recent research in our laboratory has demonstrated significant effects of food deprivation on channel catfish endocrine function. Several studies were conducted to assess the effects of food deprivation on the somatotropic and corticotropic axes in channel catfish with regard to changes in circulating hormone concentrations and the regulation of gene expression in target tissues. The results of these studies demonstrate that the somatotropic axis in fish responds to food deprivation in a manner similar to that of most terrestrial livestock. Growth hormone (GH) levels increase in circulation, hepatic GH-receptor expression decreases, and plasma concentrations of insulin-like growth factor-I (IGF-I) decrease in catfish as a result of food deprivation. However, the resulting increases in plasma GH concentrations and hepatic GH mRNA levels are much slower in channel catfish than in many other species, with no detectable increases until after 3 to 4 weeks of food deprivation. The effects of food deprivation on the corticotropic axis are less clear. Results of several studies have found cortisol levels both elevated and suppressed in circulation following periods of food deprivation. Such apparently contradictory results may be dependant upon the length of food deprivation. Our results suggest that plasma cortisol levels may be in flux during periods of extended food deprivation, possibly responding to changes in the energetic needs of the fish. Research is ongoing to assess the regulatory actions of cortisol during periods of food deprivation, as well as possible molecular mechanisms regulating cortisol production and function. These studies demonstrate that food deprivation has dramatic effects on the catfish endocrine system. Clear results of these effects are cessation of growth and weight loss, which have been linked to alterations in the somatotropic axis and impaired IGF-I production. The effects of food deprivation on the corticotropic axis are less clear. However, it appears that cortisol is differentially regulated during fasting. Physiological extremes, such as food deprivation and nutrient deficiency, serve as useful models to better understand the bi-directional relationship between endocrinology and nutrition.