Characterization of Compensatory Growth in Hybrid Striped Bass (Morone Chrysops X Morone Saxatilis): Hormones and Mechanisms PDF Download

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

Get Book

Book Description
Compensatory growth (CG) is a period of growth acceleration that exceeds normal rates after animals are alleviated of certain growth-stunting conditions. While the endocrine control of growth in fishes and other vertebrates is regulated primarily through the growth hormone (GH) D insulin-like growth factor (IGF) axis, the hormonal dynamics regulating accelerated (compensatory) phases of growth are poorly understood. We assessed whether CG responses could be induced in hybrid striped bass (HSB; Morone chrysops X Morone saxatilis) through feeding and/or temperature manipulation, and then examined whether components of the GH/IGF endocrine growth axis could be contributing to the response. We found that CG responses can be elicited in HSB following periods of 1) partial feed restriction, 2) complete feed restriction and 3) a combination of low water temperatures and complete feed restriction, with full catch-up growth being achieved in the latter. The most dramatic periods of CG were preceded by a catabolic state marked by body weight loss, hepatic steatosis, depressed hepatosomatic index values and an endocrine state of GH resistance. Upon alleviation of the growth-stunting condition, HSB displayed significant elevations in growth rate that exceeded controls by as much as 4 times. This CG response was accompanied by increases in feed intake (hyperphagia), improved feed conversion and a reversal of steatotsis and GH resistance. The onset of CG in feed manipulation studies was marked by significant elevations in total hepatic IGF-I mRNA and plasma IGF-I, indicating that elevated synthesis and secretion of the growth factor may mediate rapid growth responses. Strong correlations between systemic IGF-I and SGR suggest that circulating levels of IGF-I may serve as a biomarker of growth in HSB and perhaps other fishes. The 40kDa IGF binding protein (IGFBP) may also contribute to CG, since plasma levels increased in concordance with IGF-I and growth. Although little is.