Fig. 7

The mutually beneficial model between gut microbiota and host in ascidian H. roretzi. a The enriched metabolites in stool samples and their potential connection with host tissues without (Day 0) or with (Day 246) starvation stress. The metabolites include the pigment compounds astaxanthin and Xanthophyll, plant-like polyunsaturated fatty acids and esters, hormone signal substance, plant hormones (such as salicylic acid and stearidonic acid), C18 unsaturated fatty acids, phenylalanine, benzoate, salicylic acid, and stearidonic acid. These gut bacteria-originated metabolites likely play crucial roles on energy supports, inflammation balancing, and body defense through glucose and lipid metabolism pathways. b The putative mechanisms of the interactions between gut microbiota and host ascidians. The dashed box indicates the putative source bacteria of the metabolites. The yellow arrows indicate the upregulation of bacteria, metabolites or gene expression under starvation stress. The blue arrows indicate the downregulation of bacteria, metabolites, or gene expression under starvation stress