AUTHOR=Dong Yin , Jia Rui , Hou Yiran , Diao Weixu , Li Bing , Zhu Jian 

TITLE=Effects of stocking density on the growth performance, mitophagy, endocytosis and metabolism of Cherax quadricarinatus in integrated rice–crayfish farming systems

JOURNAL=Frontiers in Physiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.1040712

DOI=10.3389/fphys.2022.1040712

ISSN=1664-042X

ABSTRACT=<p>Red claw crayfish (<italic>Cherax quadricarinatus</italic>) is an economic freshwater shrimp with great commercial potential. However, the suitable stocking density of <italic>C. quadricarinatus</italic> is still unclear in integrated rice–crayfish farming system. Thus, this study aimed to investigate the effects of stocking density on growth performance, mitophagy, endocytosis and metabolism of <italic>C. quadricarinatus.</italic> The <italic>C. quadricarinatus</italic> was reared at low density (LD, 35.73 g/m<sup>2</sup>), middle density (MD, 71.46 g/m<sup>2</sup>) and high density (HD, 107.19 g/m<sup>2</sup>) in an integrated rice–crayfish farming system. After 90 days of farming, the growth performance of <italic>C. quadricarinatus</italic> significantly decreased in the MD and HD groups relative to that in the LD group. The HD treatment caused oxidative stress and lipid peroxidation at the end of the experiment in hepatopancreas. Transcriptome analysis showed that there were 1,531 DEGs (differently expressed genes) between the LD group and HD group, including 1,028 upregulated genes and 503 downregulated genes. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis indicated that the DEGs were significantly enriched in endocytosis and mitophagy pathways. Meanwhile, four lipid metabolism pathways, including biosynthesis of unsaturated fatty acids, fatty acid biosynthesis, glycerolipid metabolism and glycerophospholipid metabolism, exhibited an upregulated tendency in the HD group. In conclusion, our data showed that when the stocking density reached up to 207.15 g/m<sup>2</sup> in HD group, the growth performance of <italic>C. quadricarinatus</italic> was significantly inhibited in this system. Meanwhile, the data indicated that <italic>C. quadricarinatus</italic> may respond to the stressful condition <italic>via</italic> activating antioxidant defense system, endocytosis, mitophagy and metabolism-related pathways in hepatopancreas.</p>