Post-prandial changes in protein synthesis in red drum (Sciaenops ocellatus) larvae

Abstract

SUMMARY Protein synthesis is one of the major energy-consuming processes in all living organisms. Post-prandial changes in protein synthesis have been studied in a range of animal taxa but have been little studied in fish larvae. Using the flooding-dose method, we measured post-prandial changes in whole-body rates of protein synthesis in regularly fed red drum Sciaenops ocellatus (Linnaeus) larvae for 24–28 h following their daily meal. Fractional rates of protein synthesis increased from a baseline (pre-feeding) rate of 16% day–1 to a post-prandial peak of 48% day–1 ca. 8 h after feeding before declining to 12% day–1 after 24–28 h. The overall mean daily rate of protein synthesis was calculated as 27% day–1. Although suggested as energetically impossible in larval poikilotherms, our results show that rates in excess of 30% day–1 can be attained by larval fishes for a few hours but are not sustained. The average daily energetic cost of protein synthesis was estimated as 34% of daily total oxygen consumption, ranging from 19% immediately before feeding to 61% during the post-prandial peak in protein synthesis. This suggests that during the post-prandial peak, protein synthesis will require a large proportion of the hourly energy production, which, given the limited metabolic scope in fish larvae, may limit the energy that could otherwise be allocated to other energy-costly functions, such as foraging and escape responses.