Jinhui Wu

Alepes djedaba is a coastal fish species of high economic value. However, information on its early developmental biology remains incomplete, which limits its application in large-scale seed production. In this study, fertilized eggs were obtained through hormone-induced spawning. Under controlled conditions, microscopic observation and histological sectioning were used to systematically record and analyze embryonic development, larval growth characteristics, and the gonadal development potential of the artificially bred first-generation (F1) offspring. The results showed that the fertilized eggs of A. djedaba are spherical and pelagic with a single oil globule. The egg diameter is (672.02 ± 10.03) μm, and the oil globule diameter is (189.76 ± 8.82) μm. At a water temperature of 24.50–24.97 °C, embryonic development is divided into 6 periods (20 stages), taking 19 h 28 min to complete hatching with an average hatching rate of 22.9% ± 15.6%. The total length of newly hatched larvae is (1.43 ± 0.09) mm, with an average daily growth of 0.39 mm from 0 to 21 days post-hatching (DPH). Furthermore, the testes of the F1 generation cultured in captivity exhibit complete tissue structures and mature spermatozoa, while the ovaries show orderly development primarily dominated by stage II–III oocytes with some early stage IV oocytes. This confirms at the histocytological level that the artificially bred offspring possess normal gonadal development, providing strong evidence of its reproductive potential. This study clarifies the key stages of early development and the adaptability of A. djedaba in captive environments, providing critical theoretical support and basic data for subsequent large-scale seed production and larval rearing optimization.

To assess the current genetic status of cultured populations of the speckled blue grouper (Epinephelus cyanopodus) in China and to provide a scientific basis for the selective breeding of superior strains, this study utilized single nucleotide polymorphism (SNP) loci screened via whole-genome resequencing technology to analyze the genetic diversity and population genetic structure of 90 E. cyanopodus samples collected from six cultured populations in southeastern China. Comprehensive evaluation of various genetic diversity parameters indicated that all populations exhibited moderate genetic diversity with minor differences among them. Population structure analysis revealed weak genetic differentiation among populations, suggesting that anthropogenic introduction and translocation practices may be the primary factors contributing to the unclear population genetic structure. Additionally, this study identified a number of key genes associated with energy metabolism, muscle development, and environmental adaptation. The findings provide important theoretical foundations for the broodstock selection and scientific aquaculture of E. cyanopodus.

Oocyte maturation is a pivotal event in teleost reproduction that directly determines egg quality, fertilization success, and the developmental competence of early embryos. However, the transcriptional and post-transcriptional regulatory mechanisms operating within oocytes during maturation in marine teleosts remain poorly understood. In the present study, the orange-spotted grouper (Epinephelus coioides), an economically important marine aquaculture species, was used as a model. Oocytes at four distinct maturation stages were obtained by microscopically removing the surrounding follicular layers, followed by integrated mRNA-seq and miRNA-seq analyses to characterize the molecular regulatory landscape underlying oocyte maturation and hydration. The results showed that, as maturation progressed, oocyte diameter and wet weight increased significantly, accompanied by a marked decrease in Na⁺ content, a significant increase in K⁺ content, and the continuous accumulation of most free amino acids, indicating the gradual establishment of an osmotic basis favorable for oocyte hydration. Transcriptomic analysis further revealed extensive transcriptional remodeling during both the early and late phases of maturation. Differentially expressed genes were significantly enriched in pathways related to oocyte meiosis, cytokine signaling, lipid metabolism, DNA replication, cell cycle regulation, ribosome biogenesis, spliceosome function, oxidative phosphorylation, and mitochondrial activity, suggesting that oocyte maturation is a dynamic process characterized by a shift from basal growth maintenance to metabolic reprogramming, maternal transcript remodeling, and terminal maturation responses. miRNA profiling identified a large number of stage-specific differentially expressed miRNAs, including let-7d-5p, miR-22a-3p, and novel-miR-20/27/118, whose predicted target genes were mainly enriched in ribosome-related pathways, oxidative phosphorylation, DNA replication, transcriptional regulation, and signal transduction. Moreover, the miRNA–TF–mRNA regulatory network demonstrated that miRNAs may not only directly repress target genes, but also mediate hierarchical regulatory cascades through transcription factors, thereby coordinately participating in cell cycle progression, cytoskeletal remodeling, vesicular transport, and immune- and cell communication-related responses. Collectively, this study provides the first systematic temporal atlas of mRNA and miRNA regulation during oocyte maturation and hydration at the oocyte level in a marine teleost, thereby deepening our understanding of the molecular basis of meiotic resumption and egg quality formation, and offering valuable theoretical support for the optimization of artificial breeding and the identification of key molecular targets in grouper reproduction.

Epinephelus akaara is one of the aquaculture species with high commercial value in the aquaculture industry in the Asia-Pacific region. However, acute hypoxia is widespread in the intensive farming and live fish transportation of E. akaara, which seriously hinders the rapid development of the E. akaara farming industry. In this study, transcriptome sequencing (RNA-seq) was conducted on the liver tissues of E. akaara after hypoxia (0.6 ± 0.1 mg/L) for 1, 3, 6 and 9 h. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that key signaling pathways such as IL-17, HIF-1, TNF and PI3K/Akt were significantly enriched in the hypoxia treatment groups (Hy6 and Hy9). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) analyses revealed that genes linked to energy metabolism, immune response and apoptosis changed significantly in the liver and brain at 6 h and 9 h under acute hypoxia. In addition, three metabolism-related enzymes (GLU, LDH and PK) and two immune-related enzymes (ALT and AKP) all changed significantly at 6 h and 9 h, indicating that 6–9 h was the critical period for physiological stress of E. akaara. In conclusion, these results indicate that E. akaara mediated the organism’s tolerance and adaptation to hypoxic stress by regulating energy metabolism, immune response and apoptosis. This study enriches the regulatory mechanism by which E. akaara adapts to acute hypoxia and is conducive to the breeding of hypoxia-tolerant E. akaara strains.

Water-soluble pectin (WSP) is a soluble dietary fiber with a high esterification degree and certain viscosity and emulsifying properties. It has diverse bioactivities—including antioxidant, anticancer, and anti-inflammatory properties. This study aimed to investigate the in vitro antioxidant mechanisms of water-soluble pectin, and the in vivo effects of intestinal antioxidant capacity and gut microbiota composition in hybrid grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀). In an experiment involving feeding fish with WSP added to the diet, the addition of 600 mg/kg WSP promoted the activities of CAT, SOD, and GSH-Px in the grouper intestinal tract, thereby enhancing the antioxidant properties. At the phylum level, the relative abundance of Actinomycetes and Armatimonadetes decreased significantly. At the genus level, the relative abundance of Vibrio and Subdoligranulum increased significantly. In addition, antioxidant genes, inflammatory factor genes, immune genes, apoptosis genes, and genes of specific transmembrane proteins may participate in the regulation and improvement of the hybrid grouper intestinal tract. (CAT, MnSOD, and GPX), (TNF-α, IL-β, IL-6, and TGF-β), (MHC2, TLR3, KEAP1, and IKK-α), (C3, C8, C9, and P53), and (Claudin-3a, Occludin, ZO-1, and ZO-3) may regulate the intestinal function of hybrid grouper. Therefore, adding an appropriate volume of WSP to the diet is beneficial for the intestinal health of hybrid groupers.

The greater amberjack (Seriola dumerili) is a globally important aquaculture fish species belonging to the family Carangidae. However, current research on the ovarian development and regulation of the greater amberjack is limited, particularly with regard to early ovarian development in artificially bred individuals. Therefore, this study aims to analyze the ovarian transcriptomes at the primary growth stage in one-year-old fish at the chromatin nucleolar stage and two-year-old fish at the perinucleolar stage to suggest how early ovarian development takes place in artificially bred greater amberjacks. To do this, the study constructed ovarian mRNA expression profiles of different stages of artificially bred fish and identified differentially expressed genes (DEGs), Gene Ontology terms, and Kyoto Encyclopedia of Genes and Genomes pathways important for various physiological processes. A functional analysis revealed that the DEGs closely related to ovarian development were involved in cell growth and death (e.g., ccnd1, cdk1, cdc6, cdc25b, fbxo43, cdkn1a and cdkn1d), the TGF-beta signaling pathway (e.g., gdf6, bmpr1b, gsdf, amh, tgfb3, and smad6), steroid hormone biosynthesis (e.g., hsd3b1, hsd11b2, hsd17b12 and hsd20b2), and the endocrine system (e.g., mapk8a, mapk11, mapk12a, mapk13 and adcy9). These findings suggest that ovarian development is the result of the coordinated regulation of various genes responsible for various functions. This study provides a theoretical basis for exploring the underlying molecular mechanisms of early ovarian development in artificially bred greater amberjacks.

In order to explore the main regulatory genes and related pathways of growth traits, transcriptome sequencing was performed on the hypothalamus, pituitary, and liver tissues of 12-month-old greater amberjack (Seriola dumerili) with different growth rates. In total, 504 (118 up- and 386 down-regulated), 556 (283 up- and 273 down-regulated), and 699 (224 up- and 475 down-regulated) differentially expressed genes (DEGs) were identified in the hypothalamus, pituitary, and liver tissues, respectively. GO and KEGG pathway analyses revealed significant differences in the expression of several genes involved in growth, metabolism, and immune-related pathways. The mRNA expression levels of genes related to growth (ghrh, ghra, igf1), cell proliferation (fgf19, fgfr4, mapk8b, map2k4b, and map4k3), and lipid metabolism (acsl5, dgat2, lipeb, cyp7a1, and fabp10a) were up-regulated in the fast-growing (FG) group, while the cartl and sst1.1 were down-regulated. Conversely, genes associated with glycolysis (fbp1a, pklr, pgm2), citrate cycle (aclya, idh1), and immune-related pathways (irf1b, cxcl10, tnfb, lysg, ifi44, mapk11, and mapk12b) were up-regulated in the slow-growing (SG) group. These findings indicate that the FG exhibited greater lipid metabolism capacity and cell proliferation ability, while the SG expended additional energy to cope with environmental stress, with hindered growth during immune response. This study enhances our understanding of the genetic mechanisms underlying differences in growth rates and provides essential gene resources for future growth-related molecular breeding programs in greater amberjack.

Humphead wrasse, Cheilinus undulatus, is an endangered fish species with high economic and ecological value as well as natural sex change from female to male, while sexual selection occurs in breeding aggregations. In our present study, we constructed the first gap-free telomere-to-telomere (T2T) genome assembly for humphead wrasse, by integration of PacBio HiFi, ONT Ultra-long and Hi-C sequencing techniques. With 99% of the entire sequences anchored into 24 chromosomes, this haplotypic genome assembly spans approximately 1.25 Gb and presents a complete set of 48 telomeres and 24 centromeres. In terms of correctness (quality value QV: 53.447) and completeness (BUSCO score: 99.3%), this chromosome-scale assembly is indeed of high quality. We predicted 658.03 Mb of repetitive sequences and annotated 26,609 protein-coding genes in the assembled genome. This high-quality T2T genome assembly not only facilitates the genetic conservation of humphead wrasse, but also offers fundamental genomic data for supporting in-depth investigations on functional genomics, genetic diversity, and selective breeding for this economically important teleost.

Sargassum hemiphyllum is a major brown macroalga and has important ecological and economic significance. Ocean acidification and nitrogen enrichment are serious threats to marine ecosystems primarily by altering the physiology of organisms. However, the response of S. hemiphyllum to the combined effects of ocean acidification and elevated nitrogen levels remains unclear. This study conducted a 7-day dual-factor experiment to investigate the physiological and transcriptional responses of S. hemiphyllum under two CO2 levels (400 μatm and 1000 μatm) and two NO3⁻ levels (50 μmol/L and 300 μmol/L). The results showed that high CO2 and NO3- concentrations promoted the synthesis of photosynthetic pigments including qN and NPQ. Physiological results showed that high CO2 and the combined high NO3- and CO2 treatments enhanced growth rate and NO3- uptake rate, but NR activity was significantly decreased. Transcriptome analysis identified differentially expressed genes involved in oxidative phosphorylation, carbon metabolism, the TCA cycle, and nitrogen metabolic pathways. Notably, genes related to oxidative phosphorylation and TCA cycle were significantly up-regulated under high NO3- and dual-factor treatments, suggesting that carbohydrate metabolism and energy metabolism of S. hemiphyllum were significantly enhanced. The qRT-PCR analysis revealed that the expression levels of key genes involved in carbon fixation and nitrogen metabolism, including PFK, PRK, GAPDH, Rubisco, NR, and MDH, were significantly downregulated. These findings elucidate the molecular mechanisms by which S. hemiphyllum adapts to ocean acidification and nitrogen enrichment, offering valuable insights for understanding its capacity to withstand changing marine environments.