CRESPI, E.J.*; DENVER, R.J.; Univ. of Michigan, Ann Arbor; Univ. of Michigan, Ann Arbor: Food restriction during late prometamorphosis alters post-metamorphic growth, feeding behavior, and physiology in Xenopus laevis

Studies in mammals have shown that activation of the neuroendocrine stress axis in the fetus or neonate can have profound effects on basal activity and reactivity of the stress axis in the adult. Such �fetal programming� can lead to alterations in feeding behavior, growth, reproduction, and susceptibility to disease. In amphibians, environmental conditions experienced during the larval (tadpole) stage affect metamorphic timing, body size and morphology, and behavior of adults, but the physiological mechanisms that underlie these correlations are unknown. We restricted food during late prometamorphosis (decreased diet by half or food deprived for one week) and determined effects on post-metamorphic growth, feeding behavior, and whole body corticosterone content in Xenopus laevis. Food-restricted tadpoles metamorphosed at a smaller body size, but they ate more and exhibited higher juvenile growth rates than animals fed ad lib as tadpoles. Previously, we found that 4-5 days of food deprivation increased whole body corticosterone content in tadpoles. In the current study we found that this elevation persisted in juveniles through three weeks after metamorphosis (all animals fed ad lib after metamorphosis). The effects of food restriction during the tadpole stage parallel those observed in mammalian neonates that experienced stress-induced growth retardation as fetuses; i.e., catch-up growth and higher basal glucocorticoid levels. Our results suggest that the organizing effects of glucocorticoids during early development lead to long-term alterations in phenotypic expression and are conserved among vertebrates. (Supported by NSF grant IBN 0235401 to R.J.D.)