Exploring Sexual Dimorphism in the Intestinal Microbiota of the Yellow Drum (Nibea albiflora, Sciaenidae)

Most of fish species exhibit striking sexual dimorphism, particularly during growth. There are also sexual dimorphisms of internal organs and biological functions, including those of intestinal microbiota, which likely plays a key role in growth. In this study, the growth and intestinal microbiota of the female, male, and all-female Nibea albiflora (yellow drums) were comprehensively analyzed. The caged culture female and all-female yellow drums showed higher growth rates than males. A further analysis of the intestinal microbiota showed a significant difference in diversity between females and males in the summer, whereas there were no significant differences in the diversity and richness between females and males in the winter. In contrast, a significant difference in richness was observed between all-female and male fish, regardless of the season. Although the main composition of the intestinal microbiota showed no significant sex differences, the community structure of the intestinal microbiota of yellow drums did. Furthermore, the correlations between intestinal microbial communities are likely to be influenced by sex. The ecological processes of the intestinal microbial communities of the yellow drums showed clear sexual dimorphism. Further network analysis revealed that, although the main components of the network in the intestinal microbiota of female, male, and all-female fish were similar, the network structures showed significant sex differences. The negative interactions among microbial species were the dominant relationships in the intestinal ecosystem, and Bacteroidetes, Firmicutes, and Proteobacteria were identified as the functional keystone microbes. In addition, the functional pathways in the intestinal microbiota of yellow drums showed no significant sexual or seasonal differences. Based on the findings of this study, we gain a comprehensive understanding of the interactions between sex, growth, and intestinal microbiota in yellow drums.

Species Composition and Assemblages of Ichthyoplankton in Sansha Bay, Fujian Province, China

Sansha Bay (26.40−27.00°N, 119.50−120.20°E) is a typical semi-enclosed bay, located in northern Fujian Province, China, and adjacent to the East China Sea. The ichthyoplankton species composition and assemblage structure were investigated based on monthly sampling at 25 stations in April−September 2019, covering the important spring and summer spawning seasons in the region. Sampling was conducted in the first 3−5 days of the full moon or new moon phases using a standard plankton net through horizontal and vertical tows during daytime. In total, 25,819 ichthyoplankton samples were collected, of which 25,449 samples (i.e., 24,757 eggs and 692 larvae) were from horizontal tows. For horizontal tow samples, the ichthyoplankton were classified into 58 taxa in 15 orders and 23 families with a combination of external morphology and DNA barcoding analyses, from pelagic to demersal and benthic species. The dominant order was the Gobiiformes, including 23 species (39.7% of all species). The dominant taxa, in terms of relative abundance and frequency of occurrence, consisted of commercially important fishes, such as Setipinna tenuifilis (Valenciennes, 1848) (Engraulidae), Epinephelus akaara (Temminck and Schlegel, 1842) (Serraenidae), Collichthys lucidus (Richardson, 1844), Nibea albiflora (Richardson, 1846) (Sciaenidae), Acanthopagrus schlegelii (Bleeker, 1854), and Pagrus major (Temminck and Schlegel, 1843) (Sparidae), accounting for 78.9% of the horizontal tow samples. Low-valued and small-sized fishes, such as Stolephorus commersonnii Lacepède, 1803 (Engraulidae), Solea ovata Richardson, 1846 (Soleidae), Nuchequula nuchalis (Temminck and Schlegel, 1845), and Photopectoralis bindus (Valenciennes, 1835) (Leiognathidae), were also dominant species, accounting for 11.4% of the horizontal tow samples. The ichthyoplankton assemblage was categorized into five different temporal assemblages based on the cluster and nonmetric multidimensional scaling analysis, namely, April, May, June, July, and August−September (ANOSIM, Global R = 0.656, p < 0.01) with the highest density and richness of ichthyoplankton occurred in May. The spatial distribution pattern showed that the high density (ind./m3) of ichthyoplankton occurred mainly in S12–S25 in Guanjingyang and along the Dongchong Peninsula coastline into Dongwuyang, while low density occurred mainly in S01–S11 in the northwest waters of Sandu Island (ANOVA, F = 8.270, p < 0.05). Temperature, salinity, and chlorophyll a were key factors structuring the ichthyoplankton assemblages in Sansha Bay. In addition, this study revealed the changes of the ichthyoplankton composition, density, and spatial distribution in Sansha Bay over the past three decades.

Comparative Analysis of Intestinal Bacterial Communities in Healthy and Diseased Nibea albiflora

Background: The gut microbiota is an integral part of the host and plays an important role in both growth and development of host. The research on intestinal microbiota of Nibea albiflora and its relationship to fish disease have not been reported before. This study aimed to investigate the composition and differences of gut bacteria between healthy and diseased Nibea albiflora. Methods: The intestines were collected from forty fish (twenty healthy fish and twenty diseased). Total DNA was extracted and then amplified by nested PCR. The PCR product was subjected to the DGGE test and performed at the IlluminaMiseq sequencing. Result: The obtained results of both utilized techniques (DGGE and Next generation sequencing) showed that dominant bacteria could be grouped into four populations and the composition of intestinal bacteria differed significantly between healthy (NH) and diseased (ND) Nibea albiflora. NH has higher levels of γ-Proteobacteria and Firmicutes and with 46.91% Photobacterium supplied the dominant genus in NH. Fusobacteria and Bacteroidetes were higher in ND and Cetobacterium occupied 62.31% and was the dominant genus in ND. More probiotics were detected in NH, such as Lactobacillus, Brevibacillus, Enterococcus and Lactococcus (occupying 1.77% -19.76%), while less than 0.2% were detected for both in ND. More genera that belonged to Vibrionaceae, such as Enterovibrio (9.27%) and Vibrio (2.17%), were detected in ND and their abundances in NH were 0.79% and 0.03%, respectively.

Transcriptome Profiling Reveals a Divergent Adaptive Response to Hyper- and Hypo-Salinity in the Yellow Drum, Nibea albiflora

The yellow drum (Nibea albiflora) is an important marine economic fish that is widely distributed in the coastal waters of the Northwest Pacific. In order to understand the molecular regulatory mechanism of the yellow drum under salinity stress, in the present study, transcriptome analysis was performed under gradients with six salinities (10, 15, 20, 25, 30, and 35 psu). Compared to 25 psu, 907, 1109, 1309, 18, and 243 differentially expressed genes (DEGs) were obtained under 10, 15, 20, 30, and 35 psu salinities, respectively. The differential gene expression was further validated by quantitative real-time PCR (qPCR). The results of the tendency analysis showed that all DEGs of the yellow drum under salinity fluctuation were mainly divided into three expression trends. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the PI3K-Akt signaling pathway, Jak-STAT signaling pathway as well as the glutathione metabolism and steroid biosynthesis pathways may be the key pathways for the salinity adaptive regulation mechanism of the yellow drum. G protein-coupled receptors (GPCRs), the solute carrier family (SLC), the transient receptor potential cation channel subfamily V member 6 (TRPV6), isocitrate dehydrogenase (IDH1), and fructose-bisphosphate aldolase C-B (ALDOCB) may be the key genes in the response of the yellow drum to salinity stress. This study explored the transcriptional patterns of the yellow drum under salinity stress and provided fundamental information for the study of salinity adaptability in this species.