Environmental sex reversal in parrotfish does not cause differences in the structure of their gut microbial communities

Abstract

Parrotfish are a common fish in coral reef areas, but little is known about their gut microbial communities. In addition, parrotfish are capable of sex reversal, usually some males are sexually reversed from females, and it is still not known whether this sex reversal leads to significant changes in gut microbial communities. In this study, we investigated the gut microbial communities of three species of parrotfish including Scarus forsteni (4 females and 4 sex-reversed males), Scarus ghobban (5 females and 5 sex-reversed males), and Hipposcarus longiceps (5 females and 5 sex-reversed males) by using high-throughput sequencing technology. The gut microbial communities of these three species were mainly composed of Pseudomonadota (class Gammaproteobacteria) and Bacillota, while at the family level, they mainly included Vibrionaceae, Burkholderiaceae, Enterobacteriaceae, Streptococcacea, and Erwiniaceae. Although at the genus level, there were a large number of unclassified lineages, the remaining gut microorganisms were mainly composed of Vibrio, Photobacterium, Enterococcus and Lactococcus. Furthermore, we did not find significant differences in gut microbial community structure between the female parrotfish and corresponding female reversed males within each species, even in terms of the structure of gut microbial functional information obtained from 16 S rRNA gene sequence predictions. However, the gut microbial communities of these three species of parrotfish differed significantly not only in their community structure but also in their microbial functional information structure, mainly in terms of aspartate and asparagine biosynthesis, histidine degradation, inositol degradation, heptose biosynthesis, chitin derivatives degradation, enterobactin biosynthesis, and thiazole biosynthesis. Our study provides essential gut microbial community data for understanding the physiology and sex reversal phenomenon in parrotfish.

Keywords: 16S rRNA gene sequence; Gut microflora; Microbial communities; Parrotfish; Sex reversal.

Fig. 1

Information and photographs of sampling sites for the three species of parrotfish. The three sampling sites are as follows (a): East Island, Yongle Island, Dongsha Islands. In total, we collected three species of parrotfish: female (left ♀) and male (right ♂) Forsten’s parrotfish (Scarus forsteni) from East Island (b), female and male Blue-barred parrotfish (Scarus ghobban) from Dongsha Islands (c), and female and male Longnose parrotfish (Hipposcarus longiceps) from Yongle Island (d)

Fig. 2

Comparisons of four α-diversity indices. Shannon index (a),Pielou evenness index (b), and Chao1 index (c), of the 28 parrotfish gut samples. We also calculated and compared these three α-diversity indices in the gut microbial communities of females and males from S. forsteni, S. ghobban, and H. longiceps, respectively, the male samples here refer to males after sexual reversal. The significance of the differences was determined using the Wilcoxon rank-sum test. A single asterisk (*) indicates a significant difference at the 0.05 level, a double asterisk (**) indicates a significant difference at the 0.01 level. These results were obtained from the ASVs datasets

Fig. 3

Comparisons of four α-diversity indices, Shannon index (a), Pielou evenness index (b), and Chao1 index (c), of the 28 gut specimens from S. forsteni, S. ghobban, and H. longiceps. The significance of the differences was determined using the Wilcoxon rank-sum test. A single asterisk (*) indicates a significant difference at the 0.05 level, a double asterisk (**) indicates a significant difference at the 0.01 level. These results were obtained from the ASVs datasets

Fig. 4

NMDS analysis of the gut microbial communities separated the samples into three principal groups corresponding to the parrotfish species Scarus forsteni, Scarus ghobban, and Hipposcarus longiceps. Results were derived from the ASVs datasets, with the left (stress = 0.07) and right (stress = 0.067) plots calculated using the Bray-Curtis dissimilarity index and Jaccard similarity index, respectively

Fig. 5

Gut microbial community members of S. forsteni, S. ghobban, and H. longiceps at the phylum level. F refers to female samples and M refers to male following sex reversal samples

Fig. 6

NMDS analysis of the gut microbial functional communities separated the samples into three principal groups, one composed of the gut samples of Scarus forsteni, a second group composed of gut samples from the Scarus ghobban, and a third group composed of gut samples from Hipposcarus longiceps. The results are based on the functional information predicted by PICRUSt2 using the KEGG database. The plots on the left (stress = 0.099) and right (stress = 0.095) were calculated using the Bray-Curtis dissimilarity index (a) and the Jaccard similarity index (b), respectively

Fig. 7

Top 10 differential function information between different species of parrotfish. a: S. forsteni vs. S. ghobban; b: S. forsteni vs. H. longiceps; c: S. ghobban vs. H. longiceps; The functional information was predicted by PICRUSt2 based on the indicator ASVs against MetaCyc database

Fig. 8

Top 10 differential function information between different species of parrotfish. a: S. forsteni vs. S. ghobban; b: S. forsteni vs. H. longiceps; c: S. ghobban vs. H. longiceps; The functional information was predicted by PICRUSt2 based on the indicator ASVs against KEGG database

Fig. 9

Top 10 differential function information between different species of parrotfish. a: S. forsteni vs. S. ghobban; b: S. forsteni vs. H. longiceps; c: S. ghobban vs. H. longiceps; The functional information was predicted by PICRUSt2 based on the indicator ASVs against COG database