Plectropomus Leopardus Research Articles

Microbispora maris sp. nov., a novel actinobacterium isolated from the gill of the leopard coral grouper (Plectropomus leopardus).

A novel actinomycete, designated strain ZYX-F-249T, was isolated from the gill of a leopard coral grouper in Yongxing Island, Hainan Province, China. Based on 16S rRNA gene sequence analysis, strain ZYX-F-249T belonged to the genus Microbispora, with high similarities to Microbispora rosea ATCC 12950T (98.7 %), Microbispora hainanensis 211020T (98.5 %), Microbispora clausenae CLES2T (98.4 %), Microbispora bryophytorum NEAU-TX2-2T (98.1 %) and Microbispora oryzaeRL4-1ST (98.0 %). Phylogenetic analysis of the 16S rRNA gene sequence of strain ZYX-F-249T showed that the strain formed a stable subclade with Microbispora rosea ATCC 12950T in the genus Microbispora. The cell wall of the novel isolate contained meso-diaminopimelic acid, while whole-cell sugars were madurose, glucose and ribose. The predominant menaquinones were MK-9(H6), MK-9(H4), MK-9(H2) and MK-9(H0). The characteristic phospholipids (PLs) were phosphatidylethanolamine, phosphatidylinositol, diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylinositol mannoside, glycophospholipids and an unknown PL. The major cellular fatty acids (>10%) were iso-C16 : 0 and iso-C18 : 0. Genome sequencing showed a DNA G+C content of 71.6%. The low average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity values demonstrated that strain ZYX-F-249T could be readily distinguished from closely related species. Based on data from these phylogenetic, chemotaxonomic and physiological characteristics, strain ZYX-F-249T represents a novel species of the genus Microbispora, for which the name Microbispora maris sp. nov. is proposed. The type strain is ZYX-F-249T (=CCTCC AA 2023030T =JCM 36778T).

Effects of cold stress on the blood-brain barrier in Plectropomus leopardus

BackgroundThe leopard coral grouper (Plectropomus leopardus) is a commercially valuable tropical marine fish species known to be sensitive to low temperatures. A comprehensive understanding of the molecular mechanisms governing its response to acute cold stress is of great importance. However, there is a relative scarcity of fundamental research on low-temperature tolerance in the leopard coral grouper.MethodsIn this study, a cooling and rewarming experiment was conducted on 6-month-old leopard coral groupers. Within 24 h, we decreased the ambient temperature from 25 °C to 13 °C and subsequently allowed it to naturally return to 25 °C. During this process, a comprehensive investigation of serum hormone levels, enzyme activity, and brain transcriptome analysis was performed.ResultsP. leopardus displayed a noticeable adaptive response to the initial temperature decrease by temporarily reducing its life activities. Our transcriptome analysis revealed that the differentially expressed genes (DEGs) were primarily concentrated in crucial pathways including the blood-brain barrier (BBB), inflammatory response, and coagulation cascade. In situ hybridization of claudin 15a (cldn15a), a key gene for BBB maintaining, further confirmed that exposure to low temperatures led to the disruption of the blood-brain barrier and stimulated a pronounced inflammatory reaction within the brain. Upon rewarming, there was a recovery of BBB integrity accompanied by the persistence of inflammation within the brain tissue.ConclusionsOur study reveals the complex interactions between blood-brain barrier function, inflammation, and recovery in P. leopardus during short-term temperature drops and rewarming. These findings provide valuable insights into the physiological responses of this species under cold stress conditions.

Transcriptome analysis reveals the dynamics of gene expression during early embryonic development of hybrid groupers

Distant hybridization is widely applied in genetic improvement of aquatic animals. Although this technique should be suitable for genetic improvement of grouper, few studies related to offspring produced via distant hybridization have been reported. There we studied the gene expression dynamics of early embryonic development of groupers from self-breeding, intraspecific breeding and intergeneric hybridization. We first obtained offspring from female brown-marbled grouper (Epinephelus fuscoguttatus) and male leopard coral grouper (Plectropomus leopardus) and described the morphological characteristics of different developmental stages of embryos. We then constructed the transcriptome maps during early embryonic development of hybrid groupers. In addition, we also found that the process of MZT occurred from high blastula to early gastrula stage in the embryo of hybrid grouper and that wnt signaling pathway play an important role in dorsal-ventral axial formation during embryonic development of grouper. These results provide a foundation for the hybrid breeding of leopard coral grouper.

Effect of Dietary Astragalus polysaccharides (APS) on the Growth Performance, Antioxidant Responses, Immunological Parameters, and Intestinal Microbiota of Coral Trout (Plectropomus leopardus)

The potential effects of Astragalus polysaccharides (APS) were evaluated in coral trout (Plectropomus leopardus). Five APS levels (0%, 0.05%, 0.10%, 0.15%, and 0.20%) were added to the diet of coral trout, and a 56-day growth trial (initial weight 18.62 ± 0.05 g) was conducted. Dietary APS enhanced growth performance, with the highest improvement observed in fish fed the 0.15% APS diet. This concentration also enhanced the antioxidant capacity and immunomodulation of the fish by regulating the expression of genes associated with antioxidant enzymes and immune responses. Intestinal microbiota analysis revealed that APS supplementation significantly increased the Chao1 index and relative abundance of beneficial bacteria (Firmicutes and Bacillus). A high level of APS (0.20%) did not provide additional benefits for growth and health compared to a moderate level (0.15%). These findings indicate that an optimal APS dose promotes growth, enhances antioxidant activity, supports immune function, and improves intestinal microbiota in coral trout. Based on a cubic regression analysis of the specific growth rate, the optimal APS level for the maximal growth of coral trout was determined to be 0.1455%.

The research of nicotinamide and β-arbutin on reducing melanin content in the skin of leopard coral grouper (Plectropomus leopardus)

Body color is an important economic characteristic of leopard coral grouper (Plectropomus leopardus). In this study, we tried to make the red color more visible on the skin by reducing the melanin level, and aimed to investigate the possible mechanism of nicotinamide and β-arbutin on reducing melanin content in the skin of P. leopardus. 0.5 % nicotinamide or 0.5 % β-arbutin was added to the basal feed formulation to feed P. leopardus for 60 days. After nicotinamide or β-arbutin added feeding, the time for P. leopardus to maintain uniform body color was significantly longer. The melanin content in the skin of P. leopardus was significantly reduced, and the number of melanin particles was reduced. In skin, the enzyme activities of superoxide dismutase (SOD) and catalase (CAT) decreased, and the content of malondialdehyde (MDA) increased. The mRNA expression of TYR, Sox10 and Mitf related to melanin synthesis and proliferation and differentiation decreased. The apoptosis-related gene Bax was upregulated, the Bcl-2 gene was down-regulated, and Bax/Bcl-2 > 1. The content of tyrosinase decreased and the content of melanin metabolizing enzyme increased, and the effect of nicotinamide was more obvious than that of β-arbutin. In summary, nicotinamide or β-arbutin added feeding increased the oxidative stress and the apoptosis level of the skin, increased the metabolism of melanin, decreased the synthesis and differentiation of melanin, thus reduced the content of melanin and the number of melanin particles in the skin. This study provided a new basis for the body color regulation of cultured P. leopardus.

Effect of background color on the growth performance, digestive enzyme activity, antioxidant capacity, and intestinal microbiota of juvenile Plectropomus leopardus

The scale of Plectropomus leopardus breeding is continually expanding, and this has necessitated constant changes to ensure that breeding conditions are optimized. Background color is an important factor affecting fish feeding. In this study, fish (10.58 ± 0.03 g) were cultured on five background colors (red, blue, black, white, and transparent), and the growth status and intestinal microbes of these fish over 56 days were analyzed. Growth performance and the expression of growth-related genes were optimized when the background color was white. The white group had higher AMS and LPS enzyme activities and lower T-SOD and T-AOC enzyme activities, indicating that the white background could effectively promote feeding and reduce oxidative stress in P. leopardus. Additionally, changes in background color altered the composition and function of the intestinal microbiota. The diversity and abundance of intestinal microbiota, including the abundance of beneficial bacteria, were highest in fish on a white background. The abundances of Firmicutes and Actinobacteriota and the abundance of Bacillus were higher in the White group than in the other groups, indicating that a white background promotes the health of juvenile P. leopardus. In conclusion, a white background can promote the growth performance of P. leopardus and increase the abundance of beneficial intestinal microbes. Generally, the results of our study could be used to optimize the culture of P. leopardus.

Dynamic changes in pigmentation-related gene expression during morphogenesis in Plectropomus leopardus revealed by comparative transcriptome analysis

Plectropomus leopardus is a valuable marine aquaculture fish, prized by consumers for its high nutritional value and gorgeous appearance. The economic significance of this species is largely influenced by its body color, prompting researchers to become increasingly interested in understanding the mechanisms behind its color formation. However, previous studies have mainly focused on the molecular mechanisms of body color formation during the adult stage of this species. In this study, it was observed that the body color of P. leopardus undergoes four distinct stages during early morphogenesis: transparent (PT), red (PR), red with spots (PRS), and brown with spots (PBS). The L*a*b* values of skin at each stage differ significantly. The number and distribution of erythrophores and melanophores play a crucial role in determining the body colors of P. leopardus. Transcriptome analysis of the skin at these stages revealed multiple differentially expressed genes (DEGs) and signaling pathways related to pigmentation. These pigmentation-related DEGs can be categorized into carotenoid metabolism-related genes (e.g., scarb1, ldlr, plin2, apod, ttc39b, etc), melanin synthesis-related genes (e.g., tyr, tyrp1, dct, pmel, slc7a11, etc), and genes related to pigment cell development (pnp, ednrb, csf1r1, sox10, bnc2). GO and KEGG enrichment analysis indicated that processes like melanin synthesis (e.g., wnt signal pathway, melanogenesis, tyrosine metabolism, etc.), lipid metabolism (e.g., cholesterol metabolism, linoleic acid metabolism, arachidonic metabolism, fatty acid biosynthesis, etc.), and pigment cell development (e.g., pigment cell differentiation, cell development, etc.) are likely involved in the body color formation in P. leopardus. Finally, we proposed a hypothesis regarding carotenoid metabolism in erythrophores and melanin synthesis in melanophores of P. leopardus skin, drawing from existing research reports and transcriptome data. Overall, this study provides a new perspective on the molecular regulatory mechanisms of body color formation in P. leopardus, laying a theoretical foundation for molecular-assisted breeding of body color traits in this species.

Changes in aerobic metabolism associated with the settlement transition for the leopard coral grouper (Plectropomus leopardus)

Metamorphosis is a critical aspect of coral reef fish ecology. This developmental milestone marks changes in form and function that permit successful transition of pelagic larvae to the demersal lifestyle on coral reefs. However, we know very little about the physiological changes that occur during this period, specifically potential changes in energetics associated with swimming. This is critical, as swimming is the mechanism by which pelagic larvae find a suitable reef on which to settle. Coral grouper larvae (Serranidae: Plectropomas leopardus) were collected at night as they came into the vicinity of a fringing reef to settle, and their physiological metamorphosis was characterized. Larvae and 24 h-settled juveniles were exposed to an endurance swimming test at ecologically relevant swimming speeds, and oxygen uptake rates were measured during activity. To describe how aerobic and anaerobic properties of tissues change during metamorphosis, we also measured whole body citrate synthase and lactate dehydrogenase activity, respectively, as well as mitochondrial density in the trunk and pectoral fins. Our approach accurately measures the oxygen uptake rates these life stages need during the recruitment process, with larvae having a 74% higher mass-specific oxygen uptake rate (ṀO2) than settled juveniles despite swimming at speeds that are only 1.5 body-lengths per second (BLs−1) faster. Citrate synthase activity significantly decreased upon settlement; as larvae had 3.7 times higher activities than juveniles, suggesting that rapid changes in aerobic metabolism of tissues may be an important process during metamorphosis in this species. In contrast, lactate dehydrogenase did not significantly differ upon settlement. These findings highlight some physiological modifications that pelagic coral grouper larvae undertake within 24 h that contribute to successfully settling onto a coral reef.

Identification of Fish Species Involved with Ciguatera Food Poisoning in Okinawan Waters by Using PCR-RFLP analysis

Ciguatera fish poisoning (CFP), known as a seafood-borne disease, is caused by consumption of fish contaminated with ciguatoxins in tropical and subtropical sea. The ciguatera fishes, Variola louti, Lutjanus monostigma and L. bohar have an absolute majority in the Ryukyu Archipelago, southwestern Japan. We developed the cluster analysis of phylogenetic tree by using mitochondrial (mt) DNA 16S rRNA sequences of V. louti, L. monostigma and L. bohar and differentiate them from morphologically similar species (L. fulviflamma, L. russellii, L. argentimaculatus, Plectropomus leopardus and V. albimarginata) in our previous study. The fish were acquired from the coastal waters of the Ryukyu Archipelago, and a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) marker of the mtDNA 16S rRNA region was used, employing the restriction enzymes BmgT120 I, Dde I, and SnaB I, to identify the fish species responsible for CFP. These results showed that a PCR-RFLP marker can be obtained more easily than a nucleotide sequence.

Metabolomic analysis revealed the inflammatory and oxidative stress regulation in response to Vibrio infection in Plectropomus leopardus.

Frequent outbreaks of infectious diseases in aquaculture have led to significant economic losses. The leopard coral grouper (Plectropomus leopardus) often suffers from vibriosis. Improving host immunity presents a superior strategy for disease control, with minimal side effects compared to the use of antibiotics, highlighting the necessity of exploring the mechanisms underlying the fish's response to pathogen infections. Here, we conducted a comparative metabolomic analysis on the livers of the P. leopardus infected with Vibrio harveyi. A total of 1124 differential metabolites (DMs) were identified, with 190, 218, 359, and 353 DMs being identified at 6, 12, 24, and 48 h post-infection (hpi), respectively. Then, based on the time series analysis, we found that the lipid metabolism pathways were modulated in response to the Vibrio infection, with an increase in the quantity of eicosanoids and gycerophospholipids (GPLs), as well as a decrease in the quantity of bile acids (BAs), vitamin D, and sex hormones. Furthermore, 13 enriched pathways involving 31 DMs were identified through KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analyses. We identified histamine, 15(S)-HpETE, and anandamide in the transient receptor potential (TRP) channels pathway, as well as (7S,8S)-DiHODE, 5S,8R-DiHODE, and 13(S)-HpODE in the linoleic acid (LA) metabolism pathway. The DM levels increased, which may be attributed to inflammation. The DMs in the thyroid hormone synthesis pathway were identified, and the contents of nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH) decreased, which may be crucial in antioxidants. Our findings highlighted the dynamic adjustments in lipid metabolism and the response to inflammation and oxidative stress during the infection of V. harveyi in P. leopardus. This study not only deepens our understanding of the metabolic underpinnings of fish immune responses but also lays the groundwork for research into functional metabolomics and mechanisms of disease resistance.

Effect of Dietary β-Glucan on Growth Performance, Antioxidant Responses, and Immunological Parameters of Coral Trout (Plectropomus leopardus)

Although β-glucan has diverse benefits for fish health, the potential adverse impacts of excessive supplementation are poorly understood. This study investigated the optimal dosage of β-glucan for coral trout and explored the adverse effects of excessive supplementation. The results revealed that moderate β-glucan supplementation (1) significantly enhanced the weight gain rate and specific growth rate (SGR); (2) significantly improved the intestinal villus length (0.10%), muscle thickness (0.05–0.15%), and α-amylase and chymotrypsin activities (0.05–0.15%); (3) significantly increased liver catalase (CAT), glutathione reductase (GR), alkaline phosphatase, complement 3, immunoglobulin M (IgM), lysozyme, serum superoxide dismutase, CAT, glutathione peroxidase, GR, total antioxidant capacity, acid phosphatase, complement 4, and IgM activities and significantly reduced malondialdehyde contents; (4) upregulated genes in the liver associated with copper-zinc superoxide dismutase (SOD-1), manganese superoxide dismutase (SOD-2), CAT, GSH-Px1a, ACP6, AKP, LZ-c, IgM, C3, and C4-b. However, 0.20% β-glucan significantly inhibited the growth performance of coral trout compared with 0.10% β-glucan. Thus, 0.10% β-glucan represents the optimal dosage for promoting growth, antioxidant activity, and immune responses in coral trout, while higher β-glucan levels weakened these beneficial effects. With an SGR established by a cubic regression analysis, the optimal level of β-glucan for maximal growth of coral trout is 0.082%. This study provides new insights into the health impacts of β-glucan on fish.

Suitable dietary phospholipids improve lipid deposition, but excessive dietary phospholipids disorder lipid metabolism in juvenile leopard coral grouper (Plectropomus leopardus)

Limited investigation has been available on the effects of dietary phospholipids in leopard coral grouper (Plectropomus leopardus), hindering its potential for aquaculture. This study was intended to investigate the impact of various levels (05 %) of dietary soy lecithin (SL) on juvenile P. leopardus over a 9-week feeding trial. Results indicated that dietary inclusion of 23 % SL enhanced the lipid content in liver, muscle, and whole-body. The fatty acid composition of muscle strongly reflected the dietary fatty acid profile. Furthermore, dietary inclusion of 3 % SL enhanced the activities of hepatic lipid synthesis enzymes [fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PD)] and lipolytic enzymes [hormone-sensitive lipase (HSL), carnitine palmitoyltransferase-1 (CPT-1)]. Additionally, the inclusion of 23 % SL upregulated the relative expression of lipid synthesis-related genes [fas, sterol regulatory element binding transcription factor 1 (srebp1)] and lipid catabolism-related genes [hsl, cpt-1, and lipoprotein lipase (lpl)] in muscle. However, increasing dietary SL levels up to 45 % led to a reduction in muscle and whole-body lipid content, and an enhance in hepatic lipid content and hepatocyte vacuolization. Moreover, dietary inclusion of 5 % SL downregulated the relative expressions of hepatic lipid synthesis-related genes (g6pd and srebp1) and lipid catabolism-related genes (lpl and hsl). Overall, including 23 % SL in the diet improved lipid metabolism and thereby enhanced lipid deposition in juvenile P. leopardus, but excessive SL (45 %) disrupted lipid metabolism.

Feed Components and Timing to Improve the Feed Conversion Ratio for Sustainable Aquaculture Using Starch.

Aquaculture contributes to the sustainable development of food security, marine resource conservation, and economy. Shifting aquaculture feed from fish meal and oil to terrestrial plant derivatives may result in cost savings. However, many carnivorous fish cannot be sustained on plant-derived materials, necessitating the need for the identification of important factors for farmed fish growth and the identification of whether components derived from terrestrial plants can be used in feed. Herein, we focused on the carnivorous fish leopard coral grouper (P. leopardus) to identify the essential growth factors and clarify their intake timing from feeds. Furthermore, we evaluated the functionality of starch, which are easily produced by terrestrial plants. Results reveal that carbohydrates, which are not considered essential for carnivorous fish, can be introduced as a major part of an artificial diet. The development of artificial feed using starch offers the possibility of increasing the growth of carnivorous fish in aquaculture.

Sws2 Gene Positively Regulates Melanin Production in Plectropomus leopardus Skin via Direct Regulation of the Synthesis of Retinoic Acid.

Opsins are a class of transmembrane proteins encoded by opsin genes, and they play a variety of functional roles. Short wavelength-sensitive opsin 2 (sws2), one of the five classes of visual opsin genes, mainly senses blue light. Previous research has indicated that sws2 is essential for melanocyte formation in fish; however, its specific role in skin color differentiation remains to be elucidated. Here, we identified the sws2 gene in a prized reef-dwelling fish, Plectropomus leopardus. The full-length P. leopardus sws2 gene encodes a protein consisting of 351 amino acids, and exhibits substantial homology with other fish species. The expression of the sws2 gene was widespread across P. leopardus tissues, with high expression in eye and skin tissues. Through immunohistochemistry and in situ hybridization analyses, we discovered that the sws2 gene was primarily localized in the rod and cone cells of the retina, and epidermal cells of the skin. Furthermore, dsRNA interference was used for sws2 gene knockdown in living P. leopardus to elucidate its function in skin color differentiation. Black-color-related genes, melanin contents, and tyrosinase activity in the skin significantly decreased after sws2 knockdown (p < 0.05), but red-color-related genes and carotenoid and lutein contents significantly increased (p < 0.05). Retinoic acid injection produced the opposite results. Our results suggested that the sws2 gene influences P. leopardus skin color regulation by affecting vitamin synthesis and melanin-related gene expression levels. This study establishes a foundation for elucidating the molecular mechanisms by which sws2 regulates melanocyte formation in fish skin.

Effects of spectral on growth, physiology, and growth axis gene expression in Plectropomus leopardus

This study examined the effect of different spectral on the growth, feeding rate, digestion, and metabolism of Plectropomus leopardus in an industrial recirculating aquaculture system. All Plectropomus leopardus (wet weight 100 g ± 0.45 g) were kept in triplicate tanks for 60 days under six different spectral full visual (400 to 800 nm), blue (450 nm), green (530 nm), yellow (590 nm), red (630 nm) spectrum, and dark. After the experiment, fish were weighed and sampled to obtain haemolymph, brain, and hepatopancreas tissues, which were used to analyze biochemical parameters and gene expression. The findings indicated that the group exposed to blue light demonstrated substantially elevated feeding rate, weight gain, specific growth rate, and reduced feed conversion ratios and visceral-somatic indexes compared to the other groups (p < 0.05). The blue light and full spectrum groups had considerably increased levels of digestive, metabolic, and antioxidant enzyme activity compared to the other groups (p < 0.05). The expression levels of GH, GHR, PACA, ADCY, IGFI, IGFIR, and IGFBP growth axis genes in the brain and liver were significantly higher in the blue light group than in the other groups (p < 0.05). The results indicate that spectral impact the growth, feeding rate, digestion, and metabolism of P. leopardus. This study revealed distinct spectra that enhanced the growth rate and increased the weight gain from feeding. Furthermore, the optimal spectral composition for recycling aquaculture of P. leopardus was clarified, thereby providing theoretical references for designing lighting strategies in indoor recycling aquaculture systems tailored to P. leopardus.

Establishment and application of a brain cell line derived from Plectropomus leopardus

Plectropomus leopardus is an economically valuable marine farmed fish. However, diseases have seriously restricted the healthy development of its breeding industry. Cell line is an important in vitro research system in the fields of disease control, environmental toxicology, nanotechnology, and so on. However, the application of marine fish cell lines is far from the expected level, and many species have not yet been reported to establish cell lines. In our study, we developed a brain cell line derived from P. leopardus, designated as PLB, and investigated its susceptibility to bacterial agents and heavy metal exposure. The findings indicated that PLB cell lines grew fastest in L-15 medium supplemented with 20 % fetal bovine serum (FBS) at 26 °C. The established cell line was identified by 18 S rRNA gene sequencing as being derived from P. leopardus. Chromosome analysis revealed that the PLB cell line had a chromosome count of 48. The transfection efficiency of PLB cells was about 27 % by liposome transfection method, indicating that PLB cell lines offer utility for conducting functional investigations of exogenous genes. In addition, the bacterial sensitivity analysis results indicated that PLB cells exhibited susceptibility to both Vibrio harveyi and Edwardsiella tarda, furthermore, PLB cells displayed heightened sensitivity towards V. harveyi in comparison to E. tarda. The outcomes from the heavy metal toxicity experiments demonstrated significant toxicity of three heavy metals (Hg2+, Cu2+ and Cd2+) towards PLB cells, with Hg2+ exhibiting the highest degree of toxicity among them. Moreover, there was a dose-dependent relationship between cell survival rate of PLB and heavy metal concentration. In summary, PLB cell lines represent a promising tool for conducting in vitro analyses of foreign gene functionality, bacterial susceptibility, and heavy metal toxicity. It helps ensure the safety of aquatic breeding environments and also supports genetic enhancements in fish fry, promoting the development of traits such as increased growth and disease resistance, which are vital for aquaculture progress.

Advancing selective breeding in leopard coral grouper (P. leopardus) through development of a high-throughput image-based growth trait

Utilizing image-based computer vision techniques, many high-throughput phenotyping methods have been employed to capture intricate growth trait characteristics, offering reliable estimates of phenotypic traits crucial for breeding programs. In this study, we explored the application of partial differential equation (PDE)-based level set approaches to introduce image-based body area percentage (IBAP) as a novel growth trait in Plectropomus leopardus, as a substitution for the traditional growth trait body weight (BW). Assessing the genetic parameters essential for robust growth trait improvement in P. leopardus breeding programs, we estimated SNP-based heritability for IBAP and BW using a comprehensive set of SNPs (673,039 SNPs with MAF >2%). Results revealed heritability estimates of 0.515 (S.E. 0.06) for IBAP and 0.542 (S.E. 0.06) for BW. Moreover, strong phenotypic and genetic correlations of 0.812 (S.E. 0.001) and 0.903 (S.E 0.021) between IBAP and BW, respectively, underscored the potential for IBAP as a surrogate trait of BW for the genetic improvement of P. leopardus. We established a linear regression model of IBAP and BW (y ​= ​−730 ​+ ​1700×, (R2 ​= ​0.71)), after rigorous assessments of linearity, normality, and homoscedasticity, to confirm model fit. Evaluation of breeding value prediction accuracies using two linear models (rr-GBLUP and Bayes B) and a non-linear (RKHS) model demonstrated the superior performance of RKHS across IBAP and BW. Exploring the impact of varied marker densities for SNP selection on genomic prediction accuracy for IBAP and BW demonstrated a threshold of 10,000 SNPs for maximal model accuracy. These findings provide essential reference information and methodological groundwork for leveraging image-based traits in P. leopardus breeding endeavors, facilitating more efficient and precise genetic improvement programs.

Intestinal microbiota and gene expression alterations in leopard coral grouper (Plectropomus leopardus) under enteritis

Enteritis poses a significant threat to fish farming, characterized by symptoms of intestinal and hepatic inflammation, physiological dysfunction, and dysbiosis. Focused on the leopard coral grouper (Plectropomus leopardus) with an enteritis outbreak on a South China Sea farm, our prior scrutiny did not find any abnormalities in feeding or conventional water quality factors, nor were any specific pathogen infections related to enteritis identified. This study further elucidates their intestinal flora alterations, host responses, and their interactions to uncover the underlying pathogenetic mechanisms and facilitate effective prevention and management strategies. Enteritis-affected fish exhibited substantial differences in intestinal flora compared to control fish (P = 0.001). Notably, norank_f_Alcaligenaceae, which has a negative impact on fish health, predominated in enteritis-affected fish (91.76 %), while the probiotic genus Lactococcus dominated in controls (93.90 %). Additionally, certain genera with pathogenesis potentials like Achromobacter, Sphingomonas, and Streptococcus were more abundant in diseased fish, whereas Enterococcus and Clostridium_sensu_stricto with probiotic potentials were enriched in control fish. At the transcriptomic level, strong inflammatory responses, accompanied by impaired metabolic functions, tissue damage, and iron death signaling activation were observed in the intestines and liver during enteritis. Furthermore, correlation analysis highlighted that potential pathogen groups were positively associated with inflammation and tissue damage genes while presenting negatively correlated with metabolic function-related genes. In conclusion, dysbiosis in the intestinal microbiome, particularly an aberrantly high abundance of Alcaligenaceae with pathogenic potential may be the main trigger for this enteritis outbreak. Alcaligenaceae alongside Achromobacter, Sphingomonas, and Streptococcus emerged as biomarkers for enteritis, whereas some species of Lactococcus, Clostridium_sensu_stricto, and Enterococcus showed promise as probiotics to alleviate enteritis symptoms. These findings enhance our understanding of enteritis pathogenesis, highlight intestinal microbiota shifts in leopard coral grouper, and propose biomarkers for monitoring, probiotic selection, and enteritis management.

Manipulation of the aquatic environment to optimize the natural spawning of sunu grouper (Plectropomus leopardus) in controlled tanks

Aquaculture within culture techniques is needed to support the optimization of a number of juveniles which sunu grouper natural spawning techniques. To optimize the natural spawning of Sunu Grouper (Plectropomus leopardus) its is needed to know in details about the environment condition. Random design method by using several treatments consisted of one factor, temperature, and consisted of four treatments which are 26, 28, 30, and 32℃ which were repeated five times. Five steps were conducting start with the preparation, acclimatization of the eggs, stocking, and hatching of the eggs, and larval maintenance. Good quality feed is required to support gonad development and egg quality during brood stock-rearing. Environmental management of culture within culture techniques is needed to support the optimization of the number of juveniles. Temperature changes made by raising and lowering the temperature are a form of stimulation that trigger spawning to occur naturally.Keywords:aquacultureaquatic environmentsunu grouper

Integrated transcriptomic and metabolomic analysis provides insights into the responses to Vibrio infection in Plectropomus leopardus

Frequent outbreaks of infectious disease in fish aquaculture have led to significant economic losses. The leopard coral grouper (Plectropomus leopardus) is an economically important fish species, but suffering from the vibriosis caused by Vibrio harveyi. Here, we used time-course transcriptomic and metabolomic analysis of the intestine and liver to investigate how the leopard coral grouper responds to the infection of the pathogen V. harveyi. We found that the differentially expressed genes (DEGs) were enriched in lipid synthesis and metabolism, DNA, RNA, and protein synthesis, and peroxisome metabolism pathways. The differential metabolites (DMs) included glycerophospholipids (GPLs), eicosanoids, bile acids (BAs), and amino acids. Further integrated analyses showed that Vibrio infection triggered the arachidonic acid (AA) metabolic process, leading to significant increases in the levels of prostaglandin J2 (PGJ2) and prostaglandin A2 (PGA2), and that this was potentially regulated by the higher expression of key genes in the AA metabolic pathway such as plaat2 and ptgs1. Moreover, the upregulation of the key genes cyp7a1, cyp27a1, and baat enhanced the BA synthesis, resulting in a significant elevation of glycocholic acid (GCA) levels in the enterohepatic circulation. Concurrently, the microbially conjugated BAs in intestine were altered, suggesting a crucial role of various BAs in defending the Vibrio infection. These findings provide novel insights into the molecular responses to Vibrio infection in the leopard coral grouper, serving as a foundation for unraveling the molecular mechanisms underlying the immune responses to Vibrio infection in fish.