Growth, food consumption, protein metabolism and environmental adaptations in fish, amphibians and reptiles
The aims of this thesis were to examine protein metabolism and growth in fish, amphibians and reptiles under a variety of experimental conditions. The effects of low and high rations on food consumption, social interaction and growth were examined in salmon parr using X-radiography. Low ratio fish had a larger inter and intra-fish variation in food consumption, growth rate and mean share of meal than high ration fish. The food conversion ratio was not significantly different between the high and low ratio groups. Protein turnover in halibut was examined using X-radiographic and 15N stable isotope methodologies. Measured protein synthesis rates of 2.02 ± 0.24% d-1 were within the range previously reported in flatfish although the protein synthesis retention efficiency of 77% was higher than most teleosts, suggesting halibut have a low protein turnover high protein growth efficiency, growth strategy. Tissue growth, protein turnover, RNA concentration and translational efficiency (kRNA) were examined in several tissues of juvenile Trachemys scripta elegans. Protein synthesis was measured using a flooding dose injection. Mean protein synthesis rates of 2.40 ± 0.35, 1.26 ± 0.13 and 1.80 ± 0.16% protein d-1 were measured in the intestine, heart and liver, while protein synthesis retention efficiencies ranged between 0.7 and 1.0 suggesting highly efficient protein growth. RNA concentrations and translational efficiencies were similar to those previously reported in fish. The effects of anoxia and recovery from anoxia on protein synthesis, RNA concentration and kRNA were examined in T. scripta elegans. After exposure to anoxia for between 1 and 3h protein synthesis rates decreased below measurable levels, while during recovery there was no significant increase in protein synthesis above normoxic controls. RNA concentrations did not change significantly during anoxia exposure except in the heart, while the kRNA had decreased to zero after between 1 and 3h of anoxia. Downregulation of protein synthesis during anoxia exposure is probably an important energy saving strategy, during anoxia induced metabolic depression.