Effects Of Four Diets On The Growth,Intestinal Microorganisms,Flavor And Nutritional Ingredients Of Octopus Vulgaris

Octopus vulgaris is one of the most important commercial cephalopods and widely distributes in southeast China.Featured with strong environmental adaptability,rich nutrition,fast growth,wide spectrum of bait,and high conversion rate,O.vulgaris has become one of the best-selling aquatic products in China and other countries.At present,the industrial cultivation of O.vulgaris can only be artificially grown from natural seed captured in the wild.Based on this background,we explored the effect of different diets on the growth,intestinal microorganisms,volatile flavor,nutritional ingredients and differentially expressed genes(DEGs)of O.vulgaris.The average daily food intake,specific growth rate,diet conversion rate,and economic benefit ratio of each group were analyzed.The intestinal contents and volatile flavor substances(VFSs),fatty acids(FAs),and amino acids(AAs)of O.vulgaris of each group were detected.RNA-Seq technology were used to sequence the muscles of each group to find candidate genes that may be related to the regulation of the muscle quality of O.vulgaris.The four nature diets were tested: Scomberomorus niphonius(fish group),Helice tridens tientsinensis(crab group),Mactra veneriformis(shellfish group),and Loligo japonica(squid group).The main contents and results are as follows:1.The effects of diet on the growth performance of O.vulgarisThe shellfish group had the highest average daily food intake,while the diet conversion rate was lower than that of the fish group and the crab group.There was a little difference in the average daily food intake between the fish group and the crab group,whereas the crab group had the highest specific growth rate and diet conversion rate.The crab group had the best economic benefits ratio.The average daily food intake,specific growth rate,diet conversion rate,and economic benefit ratio of the squid group were the lowest.2.The effects of diet on the abundance and diversity of the intestinal microbial community of O.vulgarisThrough the sequencing technology of 16 S r RNA,the numbers of OTUs in the fish group,crab group,shellfish group and squid group were 862,658,695 and 519,respectively.The abundance and diversity of the intestinal microbial community of O.vulgaris in the fish group were the highest.Ten phyla including Tenericutes,Spirochaetes,Proteobacteria,etc.were the dominant bacterial phyla in O.vulgaris.Eleven genera including Mycoplasma,Lactococcus etc.,were the dominant bacterial genera in the shellfish group with the highest average daily food intake.Five bacterium species including Vibrio,Fusibacter,etc.were the dominant bacterial species in the crab group with the highest specific growth rate.3.The effects of diet on the volatile flavor and nutritional ingredients of O.vulgarisThe VFSs,FAs,and AAs of O.vulgaris in the four groups were obviously different.The sum of volatile ketones and aldehydes was higher in the crab group than in the other groups,which could present much more flavors.All groups were abundant in unsaturated FAs,including eicosapentaenoic acid(EPA)and docosahexaenoic acid(DHA).In terms of content and variety,the FAs in the crab group were more beneficial to human health than those in the other groups.The content of each AA in the crab group was basically higher than those in the other groups and was significantly higher than that in the squid group(p < 0.05).4.The effects of diet on the gene expression of muscle of O.vulgarisThere were 967 DEGs between the crab group and the shellfish group,and 526 genes were highly expressed in the crab group.There were 1134 differentially expressed genes between the crab group and the squid group,and 510 genes were highly expressed in the crab group.There were 1390 differential genes between the shellfish group and the squid group,and there were 580 differential genes highly expressed in the shellfish group.The difference in gene expression levels between the shellfish group and the squid group was the highest.After KEGG enrichment of DEGs,signal pathways related to muscle flavor nutrition and quality were discovered: signal pathways related to FAs include FA degradation,FA metabolism,and FA biosynthesis;signal pathways related to AA metabolism include β-Alanine metabolism,AA biosynthesis,arginine biosynthesis;signaling pathways related to carbohydrate metabolism include glycolysis /gluconeogenesis.5.The selection of candidate genes for the muscle quality of O.vulgarisThrough the KEGG enrichment and co-expression analysis,the fatty aldehyde dehydrogenase family of gene members(ALDH16A1,ALDH3A2)and the long-chain acyl-Co A synthetase gene family members(ACSL3,ACSL4,and ACSL5)may be the key genes in FA biosynthesis and metabolism pathways;ASS1,ASL,ARG1 are important for regulating Arginine may play a key role;GPT and GPT2,members of the glutamate pyruvate aminotransferase family,are related to the regulation of alanine,aspartic acid and glutamate metabolism pathways;the taste of the flesh of O.vulgaris may be related to TPI and PKM,which enriched in the glycolysis/gluconeogenesis pathway.In overall,crabs are ideal diet of O.vulgaris in terms of growth performance,intestinal microorganisms,volatile flavor,and nutritional ingredients.12 DEGs such as ALDH16A1,ACSL3,ASS1,TPI may be related to the muscle quality of O.vulgaris.