EFFECTS OF SEWAGE-SLUDGE EXPOSURE ON GROWTH, FEEDING AND PROTEIN-SYNTHESIS OF DAB (LIMANDA-LIMANDA (L))

Changes in the balance between protein synthesis and protein growth may play an important part in the general response of animals to environmental stress. Protein growth and synthesis has been analysed in groups of dab, Limanda limanda (L.), fed to satiation and maintained in control and sewage sludge-exposed conditions; growth rates, feeding rates and food retention were measured over three months and protein synthesis rates of the whole bodies and individual tissues. No differences in live weight growth rate or food retention efficiencies were found. However, protein growth rates were higher in the control group compared with those exposed to sewage sludge although there appeared to be no significant differences in the rates at which proteins were synthesised Therefore, efficiencies of retention of synthesised protein may have been higher in control animals than those exposed to sewage sludge. The control animals also exhibited consistently higher protein growth rates for given levels of protein synthesis in all the tissues examined, i.e. the white muscle, liver, kidney and spleen. RNA concentrations in the tissues were largely unaffected by sewage sludge treatment and there appeared to be no change in post-translational efficiency of RNA. It is concluded that long-term exposure to sewage sludge in good feeding conditions may have reduced protein growth possibly through greater protein degradation in the tissues.