title: The effects of photoperiod and different dosages of melatonin on metamorphic rate and weight gain in Xenopus laevis tadpoles.
abstract: This study examined the effects of photoperiod and three different dosages of melatonin on the rate of metamorphosis and weight gain in Xenopus laevis. Exposure of larvae to 23L:1D resulted in lower mean body weight and a retarded metamorphic rate in comparison to larvae exposed to 1L:23D. Larvae reared in either photoperiod and treated with exogenous melatonin demonstrated a dose-dependent suppression of weight attained, with short photoperiod larvae showing a more dramatic effect. Analysis of growth patterns indicate that photoperiod and exogenous melatonin have a greater effect on weights prior to Nieuwkoop and Faber stage 56 in the development of Xenopus. Larvae exposed to 1L:23D and exogenous melatonin metamorphosed at an accelerated rate when compared to larvae exposed to 23L:1D and the same dosages of melatonin. In both photoperiod regimens an exogenous melatonin concentration of 45 micrograms/100 ml resulted in an accelerated metamorphic rate, whereas 225 and 450 micrograms/100 ml retarded metamorphic rate of larvae in comparison to controls.
authors.affiliation: Department of Biological Sciences, Clemson University, South Carolina 29634-1903.
authors.forename: M L
authors.initials: ML
authors.lastname: Edwards
authors.forename: E B
authors.initials: EB
authors.lastname: Pivorun
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D007814:Larva / Q000254:growth & development; D008027:Light; D008550:Melatonin / Q000008:administration & dosage / Q000494:pharmacology; D008675:Metamorphosis, Biological / Q000187:drug effects / Q000502:physiology*; D014982:Xenopus laevis / Q000254:growth & development*
chemical_list: D008550:Melatonin