Search Results (33)

This study multidimensionally investigates the comprehensive effects of Lactobacillus plantarum (LP)-fermented feed on growth performance, intestinal health, and metabolic regulation in Pacific abalone (Haliotis discus hannai). The results demonstrate that LP fermentation significantly alters feed’s physical properties and nutritional profile, softening texture, increasing viscosity, and emitting an acidic aroma. Notably, it enhanced contents of cis-9-palmitoleic acid, α-linolenic acid (ALA), and functional amino acids (GABA, L-histidine, and L-asparagine), indicating that fermentation optimized ω-3 fatty acid accumulation and amino acid profiles through the modulation of fatty acid metabolic pathways, thereby improving feed biofunctionality and stress-resistant potential. Further analyses revealed that fermented feed markedly improved intestinal morphology in abalone, promoting villus integrity and upregulating tight junction proteins (ZO-1, Claudin) to reinforce intestinal barrier function. Concurrently, it downregulated inflammatory cytokines (TNF-α, NF-κB, IL-16) while upregulating anti-inflammatory factors (TLR4) and antioxidant-related genes (NRF2/KEAP1 pathway), synergistically mitigating intestinal inflammation and enhancing antioxidant capacity. Sequencing and untargeted metabolomics unveiled that fermented feed substantially remodeled gut microbiota structure, increasing Firmicutes abundance while reducing Bacteroidetes, with the notable enrichment of beneficial genera such as Mycoplasma. Metabolite profiling highlighted the significant activation of lipid metabolism, tryptophan pathway, and coenzyme A biosynthesis. A Spearman correlation analysis identified microbiota–metabolite interactions (such as Halomonas’ association with isethionic acid) potentially driving growth performance via metabolic microenvironment regulation. In conclusion, LP-fermented feed enhances abalone growth, immune response, and aquaculture efficiency through multi-dimensional synergistic mechanisms (nutritional optimization, intestinal homeostasis regulation, microbiota–metabolome crosstalk), providing critical theoretical foundations for aquafeed development and probiotic applications in aquaculture. Full article

Low-coverage whole-genome sequencing (lcWGS) followed by imputation is emerging as a cost-effective method for generating a substantial number of single nucleotide polymorphism (SNP) in aquatic species with highly heterozygous and complex genomes. This study represents the first systematic investigation into the application of low-coverage whole-genome sequencing (lcWGS) combined with imputation for genotyping in Pacific abalone (Haliotis discus hannai) without a reference panel. We utilized 1059 Pacific abalone individuals sequenced at an average depth of 7.86×, as well as 16 individuals sequenced at 20×, as sample materials. To assess the genotype imputation accuracy for lcWGS without a reference panel, we simulated data with varying sequencing depths (0.5–4×) and examined the effects of sample size, chromosome length, and minor allele frequency (MAF) using BaseVar and STITCH strategies. Results showed that STITCH achieved high accuracy when the sample size exceeded 400, with a genotype correlation (R²) of 0.98 ± 0.002 and genotype concordance (GC) of 0.99 ± 0.001. Imputation accuracy plateaued when the sample size exceeded 400 and sequencing depth surpassed 1×. Chromosome length had minimal effects, with all three chromosomes achieving an accuracy of approximately 0.98. However, the accuracy for rare MAF (<0.05) was lower, falling below 0.99. A second imputation with Beagle significantly increased SNP detection by 3.9–8.3 folds for a sequencing depth of 0.5–4×, apparently without sacrificing accuracy. To our knowledge, this is the first study of lcWGS analysis conducted in abalone. The findings demonstrate that lcWGS with imputation can achieve high accuracy with moderate sample sizes (n ≥ 400) in Pacific abalone, offering a cost-effective approach for genotyping in aquaculture species. Full article

Background/Objectives: Vasa and PL10 belong to the DEAD-box protein family, which plays crucial roles in various cellular functions, such as DNA replication, DNA repair, and RNA processing. Additionally, DEAD-box family genes have also been identified as being related to gonadal development in many species. However, the function of vasa and PL10 in abalone is poorly understood on a molecular level. Methods: In the present study, we individually isolated and characterized the vasa and PL10 orthologs in Haliotis discus hannai (Hdh-vasa and Hdh-PL10). We also characterized the mRNA distributions of vasa and PL10 in various tissues from adult organisms and different embryonic developmental stages using real-time PCR (RT-qPCR) techniques. Furthermore, spatial and temporal expression of Hdh-vasa and Hdh-PL10 throughout embryonic and larval development was examined by whole-mount in situ hybridization (WMISH). Results: The two predicted amino acid sequences contained all of the conserved motifs characterized by the DEAD-box family. Homology and phylogenetic analyses indicate that they belong to the vasa and PL10 subfamilies. We found that vasa and PL10 mRNA were not solely restricted to gonads but were widely expressed in various tissues. WMISH showed that Hdh-vasa and Hdh-PL10 largely overlapped, with both being maternally expressed and specifically localized to the micromere lineage cells during early cleavage stages. By the gastrulation stage, Hdh-vasa were expressed strongly in two bilaterally symmetrical paraxial clusters, but Hdh-PL10 was dispersed in entire endodermal region. Our results suggest that Hdh-vasa-expressing cells are located as a subpopulation of undifferentiated multipotent cells that express Hdh-PL10. As such, we infer that primordial germ cells are specified from these vasa-expressing cells at some point during development, and inductive signals (epigenesis) play an important role in specifying primordial germ cells (PGCs) in H. discus hannai. Conclusions: This study provides valuable insights into the molecular characteristics and expression patterns of Hdh-vasa and Hdh-PL10, contributing to a better understanding of their roles in germ cell specification and early embryonic development in H. discus hannai. Full article

Background/Objectives: The Pacific abalone Haliotis discus hannai originated in cold waters and is an economically important aquaculture shellfish in China. Our goal was to clarify the current status of the genetic structure of Pacific abalone in China. Methods: In this study, eighteen polymorphic EST-SSR loci were successfully developed based on the hemolymph transcriptome data of Pacific abalone, and thirteen highly polymorphic EST-SSR loci were selected for the genetic variation analysis of the six populations collected. Results: The results showed that the average number of observed alleles was 8.0769 (RC)-11.3848 (DQ) in each population. The number of observed alleles in the DQ, NH, and TJ populations was significantly higher than that in the RC population. The cultivated population outside the Changshan Islands has experienced a 22.79% reduction in allele diversity compared to the wild population of DQ. The pairwise F_st values and analysis of molecular variance (AMOVA) revealed significant population differentiation among all populations except DQ and NH populations, with RC and ZZ cultured populations exhibiting the largest population differentiation (F_st = 0.1334). The phylogenetic tree and structural analysis divided the six populations into two groups (group 1: NH, DQ, and ZZ; group 2: DL, TJ, and RC), and there was no relationship between geographical distance and genetic distance. Conclusions: These results may reflect the large-scale culture from different populations in China and the exchange of juveniles between hatcheries. Different breeding conditions have led to a higher degree of genetic differentiation between the RC and ZZ populations. This study enables a better understanding of the genetic diversity and structure of current Pacific abalone populations. Full article

(1) Background: Animal growth is a complex process, involving the coordination of a wide variety of genes, non-coding RNAs, and pathways. Circular RNAs (circRNAs) belong to a novel class of functional non-coding RNAs (ncRNAs). They have a distinctive ring structure and are involved in various biological processes, including the proliferation, differentiation, and apoptosis of muscle cells. The Pacific abalone Haliotis discus hannai is an economically valuable mollusk species cultivated in China. However, the modulation of muscle growth by circRNAs in this species is poorly understood. (2) Methods: In this study, we analyzed the muscle transcriptomes of 6 H. discus hannai specimens: three small (S_HD) and three large (L_HD) groups via RNA-seq and bioinformatics technology. (3) Results: The results indicated the presence of 11,744 circRNAs in abalone adductor muscle. Furthermore, the L_HD group had 250 significantly differentially expressed circRNAs (106 upregulated and 144 downregulated) relative to the S_HD group. Moreover, the bioinformatics assessment revealed that circRNAs were related to lipid transporter activity, lipid biosynthetic process, fat digestion and absorption, the single-organism metabolic process, the thyroid hormone signaling pathway, and the hippo signaling pathway, which regulates growth. Seventeen key candidate circRNAs were identified, and a core functional circRNA-miRNA-mRNA network associated with abalone muscle growth was described. Gene expression was verified using qRT-PCR, confirming the accuracy of the RNA-seq data. (4) Conclusion: Overall, this investigation furnishes novel evidence for the potential muscle growth modulatory mechanisms in Pacific abalone. These high-quality circRNA data of abalone muscle provide a reference for functional studies on the abalone genome. Full article

The Nrf2/ARE pathway is considered the most important endogenous antioxidant signaling pathway in mammals, playing a crucial role in defending against external damage. This study investigated the functional characteristics of Nrf2 in the abalone, Haliotis discus hannai. The full-length cDNA sequence of the HdhNrf2 gene was cloned using rapid amplification of cDNA ends (RACE) technology and consists of 4568 base pairs encoding a protein of 694 amino acids. The predicted theoretical molecular weight was 77 kDa, with an isoelectric point of 4.72. Multiple sequence alignment analysis revealed the relative conservation of the HdhNrf2 amino acid sequence in H. discus hannai. The tissue expression pattern of the HdhNrf2 gene was analyzed using real-time fluorescence quantitative PCR, which showed the highest expression in the gills, followed by hemocytes, with the lowest levels in the foot and mantle. The inducible expression of HdhNrf2 and antioxidant genes in abalone under H₂O₂ stress was investigated at various time points. Furthermore, an expression vector, pET-28a(+)-rHdhNrf2, was constructed, and the recombinant protein rHdhNrf2 was obtained through induced expression and purification. These findings indicated that HdhNrf2 plays a crucial role in the defense of abalones against oxidative stress. Full article

Perlucin is a shell matrix protein that plays a significant role in regulating shell biomineralization. This study aimed to isolate and characterize the perlucin gene and analyze its expression to explore its role in shell formation, regeneration, and responses to thermal stress and starvation in Pacific abalone. The isolated full-length cDNA sequence of Hdh-Perlucin is 1002 bp long, encoding a 163-amino-acid polypeptide with a signal peptide. The mature peptide of Hdh-Perlucin contains a C-type lectin domain with signature motif and six conserved cysteine residues. Gene Ontology analysis suggests that Hdh-Perlucin exhibits carbohydrate-binding activity. Significantly higher expression of Hdh-Perlucin was observed during the juvenile, veliger, and trochophore stages, compared with cell division stage during early development. Upregulated expression was recorded from slow to rapid growth phases and during shell biomineralization, while downregulated expression was noted during starvation. Under thermal stress, expression peaked at 30 °C and 25 °C for 6 and 12 h, respectively, while consistently higher levels were observed at 15 °C throughout the experiment. This study provides the first comprehensive structural and expression analysis of Hdh-Perlucin, highlighting its roles in metamorphosis, shell formation and regeneration, and responses to heat stress and starvation in abalone. Full article

The development of a shell is a complex calcium metabolic process involving shell matrix proteins (SMPs). In this study, we describe the isolation, characterization, and expression of SMP5 and investigate its potential regulatory role in the shell biomineralization of Pacific abalone Haliotis discus hannai. The full-length Hdh-SMP5 cDNA contains 685 bp and encodes a polypeptide of 134 amino acids. Structurally, the Hdh-SMP5 protein belongs to the EF-hand-binding superfamily, which possesses three EF-hand Ca²⁺-binding regions and is rich in aspartic acid. The distinct clustering patterns in the phylogenetic tree indicate that the amino acid composition and structure of this protein may vary among different SMPs. During early development, significantly higher expression was observed in the trochophore and veliger stages. Hdh-SMP5 was also upregulated during shell biomineralization in Pacific abalone. Long periods of starvation cause Hdh-SMP5 expression to decrease. Furthermore, Hdh-SMP5 expression was observed to be significantly higher under thermal stress at temperatures of 15, 30, and 25 °C for durations of 6 h, 12 h, and 48 h, respectively. Our study is the first to characterize Hdh-SMP5 comprehensively and analyze its expression to elucidate its dynamic roles in ontogenetic development, shell biomineralization, and the response to starvation and thermal stress. Full article

Pacific abalone is a high-value, commercially important marine invertebrate. It shows low growth as well as individual and yearly growth variation in aquaculture. Marker-assisted selection breeding could potentially resolve the problem of low and variable growth and increase genetic gain. Expression of quantitative trait loci (QTLs) for growth-related traits, viz., body weight, shell length, and shell width were analyzed at the first, second, and third year of age using an F1 cross population. A total of 37 chromosome-wide QTLs were identified in linkage groups 01, 02, 03, 04, 06, 07, 08, 10, 11, 12, and 13 at different ages. None of the QTLs detected at any one age were expressed in all three age groups. This result suggests that growth-related traits at different ages are influenced by different QTLs in each year. However, multiple-trait QTLs (where one QTL affects all three traits) were detected each year that are also age-specific. Eleven multiple-trait QTLs were detected at different ages: two QTLs in the first year; two QTLs in the second year; and seven QTLs in the third year. As abalone hatcheries use three-year-old abalone for breeding, QTL-linked markers that were detected at the third year of age could potentially be used in marker-assisted selection breeding programs. Full article

Bone morphogenetic proteins (BMPs) play important roles in a lot of biological processes, such as bone development, cell proliferation, cell differentiation, growth, etc. However, the functions of abalone BMP genes are still unknown. This study aimed to better understand the characterization and biological function of BMP7 of Haliotis discus hannai (hdh-BMP7) via cloning and sequencing analysis. The coding sequence (CDS) length of hdh-BMP7 is 1251 bp, which encodes 416 amino acids including a signal peptide (1–28 aa), a transforming growth factor-β (TGF-β) propeptide (38–272 aa), and a mature TGF-β peptide (314–416 aa). The analysis of expression showed that hdh-BMP7 mRNA was widely expressed in all the examined tissues of H. discus hannai. Four SNPs were related to growth traits. The results of RNA interference (RNAi) showed that the mRNA expression levels of hdh-BMPR I, hdh-BMPR II, hdh-smad1, and hdh-MHC declined after hdh-BMP7 was silenced. After RNAi experiment for 30 days, the shell length, shell width, and total weight were found to be reduced in H. discus hannai (p < 0.05). The results of real-time quantitative reverse transcription PCR revealed that the hdh-BMP7 mRNA was lower in abalone of the S-DD-group than in the L-DD-group. Based on these data, we hypothesized that BMP7 gene has a positive role in the growth of H. discus hannai. Full article

FMRFamide-related peptides are neuropeptides involved in a wide range of biological processes, including reproduction and larval development. To characterize the involvement of FMRFamide in the reproduction and larval development of Pacific abalone Haliotis discus hannai, an FMRFamide cDNA (Hdh-FMRF2) was cloned from the cerebral ganglion (CG). Fluorescence in situ hybridization and qRT-PCR were performed for functional characterization. The Hdh-FMRF2 cDNA encoded 204 deduced amino acids that contained a putative signal peptide and four FaRP domains. The major population of Hdh-FMRF2 neuronal cell bodies was localized in the cortex of CG. Hdh-FMRF2 mRNA expression was significantly upregulated in CG during the mature stage of gonadal development and effective accumulative temperature (EAT) exposed abalone in both sexes. In the induced spawning event, Hdh-FMRF2 expression was significantly upregulated during spawning in males. However, no upregulation was observed in females, suggesting Hdh-FMRF2 might inhibit gamete release in female abalone. These results revealed Hdh-FMRF2 as a reproduction related peptide. Furthermore, mRNA expression in larval development suggested that this peptide was also involved in larval development during development of Pacific abalone. Collectively, this study provides evidence of possible involvement of an FMRFamide neuropeptide in the reproduction and larval development of Pacific abalone. Full article

Catalase is a crucial enzyme of the antioxidant defense system responsible for the maintenance of cellular redox homeostasis. The aim of the present study was to evaluate the molecular regulation of catalase (Hdh-CAT) in stress physiology, innate immunity, testicular development, metamorphosis, and cryopreserved sperm of Pacific abalone. Hdh-CAT gene was cloned from the digestive gland (DG) of Pacific abalone. The 2894 bp sequence of Hdh-CAT had an open reading frame of 1506 bp encoding 501 deduced amino acids. Fluorescence in situ hybridization confirmed Hdh-CAT localization in the digestive tubules of the DG. Hdh-CAT was induced by different types of stress including thermal stress, H₂O₂ induction, and starvation. Immune challenges with Vibrio, lipopolysaccharides, and polyinosinic–polycytidylic acid sodium salt also upregulated Hdh-CAT mRNA expression and catalase activity. Hdh-CAT responded to cadmium induced-toxicity by increasing mRNA expression and catalase activity. Elevated seasonal temperature also altered Hdh-CAT mRNA expression. Hdh-CAT mRNA expression was relatively higher at the trochophore larvae stage of metamorphosis. Cryopreserved sperm showed significantly lower Hdh-CAT mRNA expression levels compared with fresh sperm. Hdh-CAT mRNA expression showed a relationship with the production of ROS. These results suggest that Hdh-CAT might play a role in stress physiology, innate immunity, testicular development, metamorphosis, and sperm cryo-tolerance of Pacific abalone. Full article

Myostatin, also known as GDF8, is a member of the transforming growth factor-β (TGF-β) superfamily. In vertebrates, myostatin negatively regulates the growth of skeletal muscle. In invertebrates, it has been reported to be closely related to animal growth. However, knowledge concerning the molecular mechanisms involved in the myostatin regulation of molluscan growth is limited. In this study, we found that the hdh-myostatin open reading frame (ORF) comprised 1470 base pairs that encoded 489 amino acids and contained structural characteristics typical of the TGF-β superfamily, including a C-terminal signal peptide, a propeptide domain, and TGF-β region. Gene expression analysis revealed that hdh-myostatin mRNA was widely expressed at different levels in all of the examined tissues of Haliotis discus hannai. Nine single nucleotide polymorphisms (SNPs) were associated with the growth traits. RNA interference (RNAi) against hdh-myostatin mRNA significantly downregulated hdh-myostatin at days 1, 15, and 30 post injection, and the pattern was correlated with downregulation of the genes TGF-β receptor type-I (hdh-TβR I), activin receptor type-IIB (hdh-ActR IIB), and mothers against decapentaplegic 3 (hdh-Smad3). After one month of the RNAi experiment, the shell lengths and total weights increased in the abalone, Haliotis discus hannai. The results of qRT-PCR showed that the hdh-myostatin mRNA level was higher in the slow-growing group than in the fast-growing group. These results suggest that hdh-myostatin is involved in the regulation of growth, and that these SNPs would be informative for further studies on selective breeding in abalone. Full article

Tropomyosin (TPM) is a contractile protein responsible for muscle contraction through its actin-binding activity. The complete sequence of TPM in Haliotis discus hannai (Hdh-TPM) was 2160 bp, encoding 284 amino acids, and contained a TPM signature motif and a TPM domain. Gene ontology (GO) analysis based on the amino acid sequence predicted Hdh-TPM to have an actin-binding function in the cytoskeleton. The 3D analysis predicted the Hdh-TPM to have a coiled-coil α-helical structure. Phylogenetically, Hdh-TPM formed a cluster with other TPM/TPM1 proteins during analysis. The tissue-specific mRNA expression analysis found the higher expression of Hdh-TPM in the heart and muscles; however, during embryonic and larval development (ELD), the higher expression was found in the trochophore larvae and veliger larvae. Hdh-TPM expression was upregulated in fast-growing abalone. Increasing thermal stress over a long period decreased Hdh-TPM expression. Long-term starvation (>1 week) reduced the mRNA expression of Hdh-TPM in muscle; however, the mRNA expression of Hdh-TPM was significantly higher in the mantle, which may indicate overexpression. This study is the first comprehensive study to characterize the Hdh-TPM gene in Pacific abalone and to report the expression of Hdh-TPM in different organs, and during ELD, different growth patterns, thermal stress, seasonal changes, and starvation. Full article

Phage-based pathogen control (i.e., phage therapy) has received increasing scientific attention to reduce and prevent the emergence, transmission, and detrimental effects of antibiotic resistance. In the current study, multidrug-resistant Vibrio natriegens strain AbY-1805 was isolated and tentatively identified as a pathogen causing the death of juvenile Pacific abalones (Haliotis discus hannai Ino). In order to apply phage therapy, instead of antibiotics, to treat and control V. natriegens infections in marine aquaculture environments, a lytic phage, vB_VnaS-L3, was isolated. It could effectively infect V. natriegens AbY-1805 with a short latent period (40 min) and high burst size (~890 PFU/cell). Treatment with vB_VnaS-L3 significantly reduced the mortality of juvenile abalones and maintained abalone feeding capacity over a 40-day V. natriegens challenge experiment. Comparative genomic and phylogenetic analyses suggested that vB_VnaS-L3 was a novel marine Siphoviridae-family phage. Furthermore, vB_VnaS-L3 had a narrow host range, possibly specific to the pathogenic V. natriegens strains. It also exhibited viability at a wide range of pH, temperature, and salinity. The short latent period, large burst size, high host specificity, and broad environmental adaptation suggest that phage vB_VnaS-L3 could potentially be developed as an alternative antimicrobial for the control and prevention of marine animal infections caused by pathogenic V. natriegens. Full article