Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2004
Publication Date: 9/30/2005
Citation: Davis Jr, K.B., Peterson, B.C. 2005. Comparison of insulin-like growth factor-I and insulin-like growth factor binding protein concentrations of the palmetto and sunshine bass and the effects of gender and stress. Journal of the World Aquaculture Society. 36:384-392. Interpretive Summary: Growth in fish is stimulated by growth hormone (GH)from the pituitary which in turn stimulates synthesis and secretion of insulin-like growth factor-I (IGF-I)and insulin-like growth factor binding proteins (IGFBPs) from the liver. IGF-I is thought to be the most important hormone which interacts with somatic tissues and stimulates growth. Sunshine bass and palmetto bass are two hybrids produced from striped bass and white bass. Growth of the two hybrids is similar, and females grow faster than males in both hybrids. Plasma IGF-I and IGFBP concentrations of males and females were compared between the two hybrids and the effect of a low-water confinement stress was also determined. Palmetto bass had significantly higher concentrations of IGF-I and IGFBP than sunshine bass. Male palmetto bass had significantly higher IGF-I than females while there was no difference due to gender in sunshine bass. Stress resulted in a decrease in IGF-I in palmetto bass but no change in sunshine bass IGF-I concentration. No effect of gender or stress was observed in IGFBP concentration. These experiments were done on fish with immature gonads and the lack of a difference in IGF-I may have been due to the absence of gonadal hormones. Plasma IGF-I nor IGFBP concentrations alone do not explain the growth responses of hybrid striped bass.
Technical Abstract: Plasma concentrations of insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding proteins (IGFBPs) were compared between market sized sunshine and palmetto bass. Differences between male and female fish were examined and both hybrids were sampled before and after a low-water confinement stress. There was no difference in body weight between the hybrid types, however, females were significantly heavier than males in both hybrids. Plasma IGF-I concentrations were significantly higher in pre-stressed palmetto bass when compared with sunshine bass, and male palmetto bass had significantly higher IGF-I concentrations than females. Two hours after a 15-minute low-water stress, a significant decrease in palmetto bass IGF-I occurred, but there was no change in sunshine bass IGF-I concentrations. Levels of a 33-kDa IGFBP were higher in pre-stressed palmetto bass when compared with sunshine bass; however, no differences due to gender were evident for either hybrid. Two hours after a 15-minute low-water exposure, there was no change in the levels of a 33-kDa IGFBP in palmetto or sunshine bass. A more complete pattern of IGF-I, IGFBPs and IGF-I receptors may be necessary to understand the role of IGF-I in regulating fish growth.