3.2 Bacterial diversity between the two sexes
Bacterial community richness and diversity varied between female and male of P . astrigera (Table 1). The results of Student’st -test showed that bacterial α-diversity of Sobs (P< 0.05), Chao1 (P < 0.05) and Shannon index (P < 0.001) in female were significantly lower than male, whereas, Simpson index in female was significantly higher than male (P < 0.05). Meanwhile, male showed a much larger standard deviation in Sobs and Chao1 indices than female.
The PCoA results of β-diversity illustrated that bacterial community of the two different sex groups clustered independently. The results of Adonis test showed significant difference between female and male (P < 0.05,R 2 = 0.48; Figure 1) proving that the community composition and their relative abundance were distinct differences between the two sex groups, and the variation range between male is much greater than that of female.
3.3 Bacterial compositionsbetween the two sexes
The relative abundances of dominant (> 1%) gut bacteria showed apparent differences between two sexes at different taxon levels (Figure 2). At phylum level, a total of 21 phyla were identified across all data, among which, Actinobacteriota, Firmicutes and Proteobacteria were the dominant phyla in both two sexes, in addition, Cyanobacteria and Bacteroidetes were dominant in male (Figure 2a). The results of Wilcoxon rank-sum test indicated that female had a significantly higher relative abundance of Actinobacteriota and a significantly lower relative abundance of Firmicutes relative to male (P < 0.05; Figure 3a). Other phyla were all higher in male than female, though no significant difference. At genus level, a total of 168 genera were found across all data, among which 5 dominant genera belong to female, whereas 12 dominant genera belong to male (Figure 2b). The results of Wilcoxon rank-sum test showed that female had a significantly higher relative abundance of Rhodococcus and significantly lower relative abundance of Acinetobacter ,Ruminococcus and Fusicatenibacter relative to male (P < 0.05; Figure 3b). All other genera had no significant difference between the two sexes.
In agreement with composition analysis, noteworthy changes in bacterial community were found from the result of LEfSe analysis between female and male, based on relative abundance of biomarkers of bacteria (LDA Score > 4, P < 0.05; Figure 4a, b). In female, two groups of bacteria were significantly enriched, namelyRhodococcus (from phylum to genus),norank_f_norank_o_0319-6G20 (from class to genus). In male, two groups of bacteria were significantly enriched, namely Blautia (from phylum to genus),Lactobacillus(the phylum and family to genus).