The digestive system of mandarin fish (Siniperca chuatsi) can adapt to domestication by feeding with artificial diet

Abstract

Mandarin fish (Siniperca chuatsi) is an economically important aquaculture species in China. Mandarin fish prefers to feed on live prey fish and can be domesticated by artificial diet. Artificial diet culture could realize large-scale aquaculture and minimize the ecological damage caused by catching bait fish. In this study, we analyzed morphological changes and gene expression profiles of the liver, stomach, and intestines after artificial diet feeding. The skin of the domesticated mandarin fish became darker. Remarkable morphological changes in the stomach, intestines, and pyloric cecum of mandarin fish were observed. The stomach and intestinal walls of the domesticated fish became thinner, the lumen became larger, and the muscle layer became thinner. The villi of the intestines became longer and had more branches. Compared with the mandarin fish fed with live prey fish (control group), the fish domesticated by artificial diet feeding had 4194, 2505, and 4579 differentially expressed genes (DEGs) in the liver, stomach, and intestines, respectively. These DEGs were most enriched in the signal pathways of protein processing in the endoplasmic reticulum and the PI3K-Akt signaling pathway. The most significantly upregulated genes were glucokinase, microfibril-associated glycoprotein 4, and amnion-associated transmembrane protein in the liver, stomach, and intestines. The most significantly downregulated genes were insulin-like growth factor-binding protein 1, MHC class II antigen alpha chain, and neuralized E3 ubiquitin protein ligase 3 in the liver, stomach, and intestines. Twelve categories of digestive enzymes were obtained from the DEGs, including lipase, trypsin, pepsin, cathepsin, nuclease, lysozyme, aminopeptidase, chitinase, elastase, chymotrypsin, maltase, and lactase. Most of these categories were sequenced for the first time. Results suggested that mandarin fish have a certain degree of adaptability to artificial diet feeding. Multigeneration screening must be performed to obtain strains that are easy to domesticate to achieve extensive artificial diet culture.