Reciprocal effect of temperature and dietary lipids on metabolic performance and gut microbiota of Yellowtail kingfish (Seriola lalandi) juveniles

In the present study, the effect of acclimation temperature (20 and 26°C) on the metabolic and physiological performance of yellowtail kingfish (Seriola lalandi) fed different diets (7, 14 and 21% lipid inclusion) was analysed. Fish fed the 14% and 21% lipid inclusion diets (20 and 26°C) had the highest final weight (80.9 ± 4.2 and 90.0 ± 3.7 g) and specific growth rate (1.4 and 1.7) respectively. Likewise, fish fed the 21% lipid inclusion diet (26°C) had the highest postprandial metabolic rate (430.5 mg O2 h−1 kg−1), the highest ammonium excretion rate (17.8 mg NH4+ h−1 kg−1) and a lower oxygen: nitrogen ratio (10), all reflecting higher protein metabolism. In contrast, fish fed the 7% lipid inclusion diet (26 and 20°C) had the lowest metabolic and physiological performance. Lipid incorporation into the liver parenchyma was higher in organisms fed the diet with 21% lipid inclusion. The composition of the autochthonous microbiota of yellowtail kingfish consisted of the Phylum Proteobacteria, Actinobacteria, Bacteroidetes, Planctomycetes, Firmicutes and Cyanobacteria. An increase in the Shannon, observed OTUs, Pielou and Faith_ph indices was observed with respect to the decrease in lipids in the diet (7%). The families with the highest relative abundance identified in the dietary treatments were Rhodobacteraceae (diet with 7%), Propionibacteriaceae (diet with 14%) and Sphingomonadaceae (diet with 21%). With respect to the temperature, at 20°C a higher abundance of Propionibacteriaceae, Flavobacteriaceae, Microbacteriaceae and Caulobacteraceae families were found, while at 26°C, the main families were Rhodobacteraceae, Microbacteriaceae and Xanthomonadaceae.