3.1 | The faster and slower regeneratingApostichopus japonicus have different intestinal microbial communities
We assessed the intestine regeneration rate of the faster and slower regenerating A. japonicus individuals, including intestinal length and weight. The intestinal length of the faster regenerating individuals was significantly longer than that of the slower regenerating individuals during intestine regeneration (10-14 d). The intestine of the faster regenerating individuals was also heavier than that of the slower regenerating individuals (Figure 1). There were significant differences between the two groups. Thus, we assessed the intestinal microbiome of the faster and slower regenerating groups.
At 97% sequence identity, a total of 3,147 OTUs were obtained across all samples. The samples from the faster regenerating group contained 2,373 OTUs (on average), while the slower regenerating group samples contained 2,365 OTUs (on average) (Table S1). The Shannon indices were 5.69 and 4.77, and the Chao1 richness values were 897 and 688 OTUs in the faster and slower regenerating groups, respectively. The results indicated that the alpha diversity of the bacterial community was different between the faster and slower regenerating groups (F and S) (Figure S1).
Analysis of the intestinal microbiota revealed that the faster and slower regenerating individuals had distinct taxonomic compositions (Figure 2a, Figure S1). In the F samples, Flavobacteriales (average 21.3%) and Rhodobacterales (19.3%) were the most abundant orders, represented mainly by the Flavobacteriaceae (20.3%) and Rhodobacteraceae (19.3%) families, respectively. Compared to that in the F samples, a markedly varied profile was detected in the S samples (Figure 2a, Figure S1). The Micrococcales order prevailed (average 27.9%) and was represented mostly by the Microbacteriaceae (27.7%) family. Rhodobacterales (13.3%) was the next most abundant order, represented by the Rhodobacteraceae (13.3%) family. The reads affiliated with Flavobacteriales were significantly more abundant in the faster regenerating individuals than in the slower regenerating individuals (Figure 2b).