Anthropogenic carbon emissions are a major driver of ocean warming, with increasing consequences for marine species distributions and potential ecological interactions. This study investigates the cascading impacts of emission-driven climate change on the distributions and interspecific spatial relationships of ecologically important Cheilinus wrasses across the Indo-Pacific convergence zone. Using species distribution modelling (MaxEnt) under multiple future emission scenarios (RCP2.6-8.5 for the 2050s and 2100 s), we project a marked divergence in habitat suitability responses. Narrow-range species, such as C. quinquecinctus, retained core habitats while expanding at their margins, resulting in a projected net habitat gain of up to 52.82%. In contrast, the wide-ranging and functionally important humphead wrasse (C. undulatus) showed persistent internal erosion within its current range, with a projected net habitat loss of up to 8.53%. These warming-associated redistributions, primarily constrained by changes in mean salinity, were accompanied by a reorganization of the potential spatial-overlap network among congeners. The potential spatial overlap between C. undulatus and the crown-of-thorns starfish (Acanthaster planci) was projected to decline modestly under future climate scenarios. Their current high range overlap (Schoener's D = 0.864) declined to 0.828 under the 2050s RCP2.6 scenario and 0.826 under the 2100 s RCP8.5 scenario. This projected reduction in potential spatial overlap may indicate a possible climate-driven predator-prey spatial mismatch, which could reduce spatial opportunities for interaction between C. undulatus and A. planci and warrants further empirical validation. Overall, our findings indicate that carbon emission pathways may reshape the broad-scale potential distribution patterns and spatial relationships of reef-associated fishes. The projected stable suitable areas, vulnerable reef regions, and potential reduced-overlap zones provide scenario-based spatial information for future conservation assessment and field validation, rather than direct spatial prioritization or policy recommendations.

The Yangtze Estuary, a critical biogeographic barrier and major biogeographic transition zone, is under escalating pressure from climate change. This study integrates species distribution modeling, niche analysis, and multi-period future climate projections to quantify how the estuary's environmental gradients shape the vulnerability and fate of intraspecific populations in two key coastal species: the hairfin anchovy (Setipinna tenuifilis) and the Chinese mitten crab (Eriocheir sensu stricto). Results reveal that the estuary acts as an ecological filter shaped by river-sea mixing, turbidity and nutrient delivery, which form strong north-south gradients in chlorophyll-a and primary productivity. These gradients underpin distinct niche adaptations: maximum chlorophyll contributes 58.1% to the distribution of the northern anchovy population, which is mainly constrained by this factor, while minimum primary productivity dominates the niche of southern anchovy population with a contribution rate of 62.0%. Under the high-emission RCP8.5 climate scenario, intraspecific climate responses diverge sharply by 2100. The southern EJC crab lineage emerges as a "climate winner" with a net suitable habitat gain of 919,698.44 km2. In contrast, two threatened populations are identified as typical "climate losers": the southern anchovy population, where 17.17% (751,217.84 km2) of its current suitable habitat will contract with a net habitat loss of 8.91% (389,930.16 km2) after offsetting newly expanded areas; the ES crab lineage exhibits a gross habitat contraction proportion of 27.00% (287,601.94 km2) and a net habitat loss rate of 21.28% (-226,707.23 km2). Crucially, climate change will drastically reconfigure intraspecific competitive interactions. For E. sensu stricto, niche overlap area between the EJC and ES lineages surges by 103.0% (from 263,118.50 km2 to 534,084.26 km2), shifting most inter-lineage competitive pressure toward the expanding EJC lineage. For S. tenuifilis, strong inherent niche divergence and the estuary's persistent geographic barrier buffer inter-population competition, their Schoener's D niche overlap index remains consistently low, rising only slightly from the current 0.15 to 0.23 by 2100 and maintaining stable ecological isolation. These findings demonstrate that estuarine gradients pre-determine population-specific climate vulnerability and future ecological outcomes. We therefore propose an evolutionarily significant unit (ESU)-based adaptive management framework, with a core actionable policy recommendation: the southern anchovy population and ES crab lineage should be independently classified, assessed and protected as separated conservation units during marine spatial planning.

Global climate change is expected to significantly reshape marine species distributions, particularly among taxa traditionally classified as cold-water specialists. This study investigates the genus Zoarces, comprising six species, to elucidate the environmental drivers of their current distributions and predict future habitat shifts under multiple Representative Concentration Pathway (RCP) scenarios. Utilizing species distribution models and ecological niche overlap analyses, we identify key abiotic factors influencing Zoarces distributions, assess center-of-mass migration trajectories, and quantify interspecific niche dynamics in response to warming oceans. Our results reveal that Z. andriashevi exhibits a broad suitable habitat exceeding 5.49 million km2, with high-suitability zones constituting 21.5% of this area. Under the RCP8.5 scenario, its habitat is projected to expand by approximately 1.7 million km2 by 2100, reflecting strong environmental tolerance and adaptability to rising temperatures. Z. americanus maintains a wide but spatially concentrated distribution across temperate regions of the eastern USA, western Europe, and the Yellow and Bohai Seas. In contrast, Z. fedorovi and Z. gillii display restricted range characteristics, with Z. gillii-the earliest diverged lineage-primarily inhabiting the relatively warmer Yellow and Bohai Sea regions, where its suitable habitat is contracting under climate warming. Crucially, ecological niche analyses reveal that Zoarces species exhibit complex patterns of niche divergence and convergence under future climate scenarios. Notably, niche separations are predicted between Z. americanus and both Z. viviparus and Z. elongatus, while significant niche integration is projected between Z. americanus and Z. fedorovi, suggesting intensified interspecific competition. Collectively, these findings challenge the prevailing assumption that Zoarces are strictly cold-water origin species. Instead, their distributional and phylogenetic evidence supports a warm-temperate origin with subsequent adaptations to colder environments. This study provides a rigorous theoretical framework for understanding Zoarces' evolutionary ecology under climate change and informs biodiversity conservation and sustainable management strategies within this genus.

The Spotted knifejaw was previously considered a predominantly carnivorous species, but emerging evidence suggests that it exhibits omnivorous characteristics. However, the mechanisms underpinning its dietary remain poorly understood; Behavioral experiments have demonstrated that the fish shows preferences for both carnivorous and herbivorous foods and olfactory dysfunction was found to significantly reduced the responsiveness to food stimuli. Anatomical and histological analyses revealed a well-developed olfactory system, with increases in the number of olfactory lamellae and epithelial cells at 50 and 120 dph, which were consistent with spatio-temporal gene expression patterns. Genomic analyses identified ORs within the GPCR family, including 164 MORs, 77 TAARs, 4 V1Rs, and 7 V2Rs. Notably, a significant expansion of the δ subtype of MORs was observed suggesting a role in omnivorous adaptation. Transcriptomic WGCNA revealed the pathways related to protein digestion and absorption, pancreatic secretion, olfactory transduction, and gastric acid secretion. It is hypothesized that the expansion of TAAR13c is related to the carnivorous nature of O. punctatus. In situ hybridization confirmed the expression of key ORs in olfactory epithelial cells, sensory neurons, and intestinal endocrine cells, and functional validation of ORs using the dual luciferase assay, providing new insights into the molecular mechanisms governing omnivory in the Spotted knifejaw.

Spotted knifejaw (Oplegnathus punctatus), an economically important species in marine aquaculture, employs a unique sex determination mechanism based on a complex sex chromosome system (X1X1X2X2/X1X2Y). Males (2n = 47) possess one fewer chromosome than females (2n = 48), and their karyotype includes an unusually large neo-Y chromosome. Additionally, a pronounced sexual dimorphism in growth rate is observed, with males exhibiting a faster growth rate than females. In this study, we conducted a comprehensive whole-genome scan, which initially revealed structural variations in the anti-inflammatory itih4 gene between male and female O. punctatus. Additionally, we designed a pair of primers to detect DNA sequence variations within the itih4a/itih4b gene. These variations are located in the intergenic region of the fusion Y chromosome in male O. punctatus, compared to the homologous X chromosome in females. In females without DNA insertions in the itih4a/itih4b intergenic region, a single band of 351 bp is amplified. By contrast, in males with DNA insertions, two bands are amplified (755 bp and 351 bp). The 755 bp band specifically indicates the presence of a DNA insertion in the itih4a/itih4b intergenic region on the Y chromosome, associated with male-specific genetic traits. Our study will facilitate the rapid identification of the genetic sex of both male and female O. punctatus individuals.

Oplegnathus fasciatus is a commercially important marine fish species, valued both in wild fisheries and aquaculture. It possesses a multivalent sex-determination system (X1X1X2X2/X1X2Y) and exhibits marked sexual growth dimorphism, with males demonstrating significantly faster growth rates. Sex-specific molecular markers are instrumental in advancing selective breeding strategies. In this study, whole-genome screening of O. fasciatus revealed a male-specific structural variant within an intronic region of ndc80: two insertions of 3bp and 538bp (totaling 541bp), which were consistently absent in females. To facilitate practical application, we developed a PCR-based assay using a single primer pair that amplifies a conserved region flanking the insertion site. This assay reproducibly generates distinct banding patterns: males yield two fragments (208bp and 749bp), consistent with the 541bp male-specific insertion, whereas females yield only the 208bp amplicon. This method enables efficient, high-throughput sex identification in O. fasciatus without the need for sequencing. Using standard agarose gel electrophoresis, the assay reliably distinguishes sexes through clearly divergent banding patterns. Beyond applications in selective breeding, these sex-specific markers provide critical molecular insights into the sex determination mechanisms and the genetic basis of sexual dimorphism in O. fasciatus.

Turbot (Scophthalmus maximus) is an economically important farming fish in China. However, an emerging disease named turbot acute hemorrhage disease (TAHD) has been affecting turbot farms since November 2019. TAHD is characterized by severe bleeding in the fish fins and may lead to significant mortality in one or two weeks, with accumulated mortality exceeding 90 %. The TAHD spread rapidly across the major turbot farming regions in China and resulted in significant economic losses. Virome sequencing was utilized in the diseased fish to discover a novel turbot circovirus (TCV). The TCV particle is similar to 30 nm in size and is located in the fish spleen and kidney. The TCV genome is 1774 bp long, with three open reading frames (ORFs) encoding the replication protein (Rep), capsid protein (Cap), and ORF3 of unknown function. The identity of the TCV Rep sequence was <53 % compared to the reported circovirus sequences. Phylogenetic analysis of the Rep and Cap protein sequences revealed that TCV is a novel circovirus. The polymerase chain reaction detection method was used to analyze the clinical TAHD samples from 2019, which were all TCV-positive. Various cell lines, including turbot kidney, epithelioma papilloma cyprinid, Chinook salmon embryo, and spotted halibut kidney, were used for TCV isolation. However, no cytopathic effect or replication was observed. The diseased fish tissue homogenate filtrate was used for experimental infection. As a result, all of the infected turbot showed signs of natural infection, with increasing numbers of cap gene copies post-infection. Based on these results, it was hypothesized that the novel circovirus TCV is closely associated with TAHD. Our research also indicated that the circovirus represents a significant threat to fish and more attention should be paid to it in aquaculture.

Wnt family genes encode secreted glycoproteins that regulate cell proliferation, differentiation, and organ growth. While much research has focused on species with standard chromosomal systems, there is a lack of studies on marine fish species like Spotted knifejaw (Oplegnathus punctatus), which possess a multiple sex chromosome system (X1X1X2X2/X1X2Y). We employed a combination of whole-genome scanning of the Wnt family, and qPCR analyses, RNAi knockdown to assess the specific contribution of wnt4 to female sexual development. We identified 16 Wnt genes in the Spotted knifejaw, with OpWnt2, OpWnt3, OpWnt4, OpWnt7, OpWnt8, OpWnt9, and OpWnt10 exhibiting two genotypes in females, while OpWnt4 and OpWnt9 had only one sequence in males. Phylogenetic analysis grouped the Wnt family into three clusters: OpWnt2/OpWnt5, OpWnt1/OpWnt6/OpWnt4, and OpWnt3/OpWnt8/OpWnt10/OpWnt7/OpWnt9/OpWnt11/OpWnt16. All members of the Wnt family contain a Wnt1 domain. Wnt4 showed higher expression in female ovaries (5-40 dph) compared to males and may act upstream of foxl2, which also regulates female differentiation. Chromosomal localization of Opwnt4 was found on female chromosome 3 and male heterozygous chromosome 1. Knockdown of wnt4 upregulated male-biased genes (amh, dmrt1, sox9a) while enhancing female-biased genes (foxl2, cyp19a, cyp19b), indicating that Opwnt4 synergistically regulates female differentiation and antagonizes male pathways. This study provides new insights into wnt4's role in sexual differentiation and lays the foundation for future research on sex chromosome systems in marine fish.

Understanding species' response mechanisms to climate change is fundamental for predicting future biodiversity patterns and formulating conservation strategies. This study utilized the Maxent model to examine the effects of global warming on the suitable habitat distribution of representative benthic euryhaline Lateolabrax species. By integrating current environmental variables with projected data under four future climate scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5), we predicted changes in their suitable habitats, centroid shifts, and niche overlaps. The results revealed that the suitable habitat of L. maculatus is primarily shaped by primary productivity and distance offshore; L. japonicus shows sensitivity to maximum light intensity and seawater temperature; whereas offshore distance and seawater iron ion concentration are key determinants for L. latus. Among the three species, L. latus demonstrated the greatest adaptability, maintaining a relatively stable and even expanding suitable habitat under future climate scenarios, with minimal adverse effects from global warming. In contrast, suitable habitat areas for L. maculatus and L. japonicus exhibited varying degrees of contraction. Over time, niche overlap-including both ecological niche and geographic range overlap-generally decreased among the three species, indicating enhanced niche differentiation and spatial segregation. Additionally, the distribution centroids of L. japonicus and L. maculatus shifted poleward, with L. maculatus experiencing the largest centroid shift-approximately 1793 km northward under the 2100 RCP8.5 scenario. This study provides valuable scientific insights into the responses of Lateolabrax species to climate change and their projected distributional dynamics, offering a critical foundation for the conservation and sustainable management of Lateolabrax resources.

Taxonomic studies demonstrated that Tridentiger bifasciatus and Tridentiger trigonocephalus were homologous species with highly analogous external morphology, which rendered them challenging to distinguish from one another. The results of species distribution modeling indicated that T. bifasciatus and T. trigonocephalus exhibited significant overlap in their distribution points and suitable habitats, primarily concentrated in areas where freshwater and saltwater converge at river mouths. This paper presented a T. bifasciatus and T. trigonocephalus species-specific marker, specific primers, applications, and a method for rapid identification in species identification to overcome the inadequacy of existing detection techniques for species identification of T. bifasciatus and T. trigonocephalus. A pair of primers could be used to amplify two DNA fragments of 497 bp and 644 bp with a difference of 147 bp in T. bifasciatus and T. trigonocephalus individuals, only a single DNA fragment of 497 bp in T. bifasciatus individuals and 644 bp in a T. trigonocephalus. The DNA of individuals of T. bifasciatus and T. trigonocephalus could be amplified and resolved by agarose gel electrophoresis, reducing the time required for the identification of T. bifasciatus and T. trigonocephalus. Tridentiger species, reducing the time required for the accurate identification of T. bifasciatus and T. trigonocephalus, and improving the efficiency of species identification detection. This method provides an efficient, rapid, and accurate identification of T. bifasciatus and T. trigonocephalus species. It is significant and valuable for accurately assessing fishery resources and conserving biodiversity of T. bifasciatus and T. trigonocephalus. Additionally, it improves knowledge of sustainable replenishment of the resources of T. bifasciatus and T. trigonocephalus.

The fish species Oplegnathus fasciatus exhibits an X1X1X2X2/X1X2Y sex determination mechanism. This species holds considerable economic value and displays pronounced sexual dimorphism in growth. Therefore, the development of a rapid and accurate method for sex identification is critical to enhancing breeding efficiency and maximizing production value. Using third-generation PacBio whole-genome sequencing, we identified a homologous region in the samd3/elf3 intergenic region of the X and Y chromosomes of O. fasciatus. Analysis of the whole-genome sequence revealed a large DNA insertion marker fragment within this region. Using specifically designed primers, two bands of 390 bp and 1008 bp were successfully amplified in males, whereas only a single 390 bp band was detected in females. This marker can be easily distinguished by agarose gel electrophoresis, greatly enhancing the efficiency and accuracy of sex identification. This study not only expands the molecular marker system for sex identification of O. fasciatus but also offers a valuable methodological reference for sex identification in other economically important fish species. These findings have significant implications for germplasm improvement and efficient selection in aquaculture.

Sex determination mechanisms vary significantly across different chromosomal systems and evolutionary contexts. Nonetheless, the regulatory framework governing the multi-sex chromosome system (X1X1X2X2/X1X2Y) remains enigmatic. Through an examination of sex-related genes (dmrt1, hsd11b2, amh, sox9a, sox9b, foxl2, cyp19a), hormonal influences (E2, 11-KT), and histological analyses of gonadal development, we demonstrate that the critical period for sexual differentiation occurs between 35 to 60 days post-hatching (dph). Our multi-omics analysis identified amhr2 as a candidate sex-determining gene, revealing that the males possess three distinct amhr2 transcripts (amhr2ay, amhr2by, amhr2cy), whereas females express only one (amhr2a). In situ hybridization assays demonstrated that amhr2 is predominantly localized to primary spermatocyte and Sertoli cells of male testes. Notably, the specific mRNA expression of amhr2 is significantly enriched in amhr2cy, whose extracellular domain exhibits the highest binding affinity for Amh protein, with sexual expression differences manifesting as early as 5 dph. The outcomes of amhr2 interference (RNAi) experiments indicate that amhr2 knockdown leads to a reduction in the expression of male-related gene (dmrt1, amh, sox9a, sox9b), androgen synthesis genes (hsd11b2, cyp11a), and female-related genes (wnt4, foxl2, cyp19a, cyp19b). Conversely, overexpression of amhr2 yielded contrasting results. Our research supports the role of amhr2 as a pivotal candidate sex-determining gene. Furthermore, the dosage effect of amhr2, reflected in transcript abundance, mRNA expression levels, and binding efficacy, serves as a fundamental mechanism driving male differentiation and regulatory processes in Spotted knifejaw.

The oviduct gland of cartilaginous fish (sharks, skates, and chimeras) synthesizes a highly cross-linked biomaterial that forms a protective leathery egg case, commonly known as "mermaid's purses." Understanding the tissue structure of this organ is critical for elucidating the synthesis process of this promising material. In this study, we performed a histological investigation of the oviduct gland in an oviparous skate, Okamejei kenojei, using paraffin sectioning to generate three-dimensional morphological data. A total of 654 tissue sections were collected and made open source. Our results reveal that the oviduct gland of O. kenojei exhibits a typical zonal structure. The club and papillary zones account for 7.74% ± 7.58% of the gland, while the baffle zone, the largest region, comprises 25-30 layers of glandular ducts, including serous gland ducts (64.72% ± 5.86%) and mixed-type ducts (0.95% ± 1.74%), predominantly distributed along the lateral margins. The terminal zone represents the smallest region, accounting for 2.17% ± 0.54% of the gland. These findings enhance our understanding of the secretion mechanisms involved in the formation of this natural biomedical material. They also provide a foundation for further studies on marine biological histology and the development of biomimetic materials through comparisons with the oviduct glands of other cartilaginous fish.

Egg cases in oviparous cartilaginous fishes (sharks, rays, and chimaeras) exhibit diverse morphologies that are closely tied to species-specific reproductive adaptations. However, the diversity and formation mechanisms of these structures remain poorly understood. In this study, we performed a quantitative morphological analysis of egg cases from three species: Okamejei kenojei, Cephaloscyllium sarawakense, and Chiloscyllium plagiosum. The results demonstrated that the egg cases of these species could be distinguished using multiple morphological indices (p < 0.05), supporting species-specificity in egg case morphology. In these species, we observed that egg jelly initially envelops the egg case during early embryonic development and later dissolves, allowing seawater entry-suggesting a conserved reproductive strategy within Elasmobranchii. Furthermore, under artificial breeding conditions, observations of female O. kenojei showed that ovulation occurs before egg case secretion. Specifically, eggs reach the oviduct above the oviducal gland when about half of the egg case has formed. Immunohistochemical staining revealed estrogen and progesterone receptors in the oviductal gland cells. Interestingly, O. kenojei can produce malformed eggs with shark egg case-like features under captive breeding conditions. These findings provide new insights into the species-specificity, timing, and hormonal regulation of egg case formation in cartilaginous fishes, and lay a foundation for future research on their reproductive strategies.

Cartilaginous fishes (sharks, skates and chimaeras) exhibit diverse behavioral patterns and unique endoskeleton, which provide insights into their ecological adaptations and evolution. However, research on the development of cartilaginous fish is still limited. To evaluate the relationship between embryonic behavior and cartilage development in cartilaginous fishes, the developing Okamejei kenojei was analyzed through behavioral, anatomical, and histological approaches, with an atlas of embryonic behavior and skeletal morphology. The result shows that the behavior of skate embryos evolves from early rhythmic movements to vigilance behavior to external stimuli. Data from Alcian blue and Alizarin red staining and histology sections showed that the vertebrae are the earliest regions to mineralize, with the mineralization process starting at the neural arch area and expanding along the body axis. In the anterior area, mineralized structures spread along the synarcual and neurocranium towards the pectoral fins and fin rays. Interestingly, a novel branching pattern of fin rays was observed in the pectoral fins of embryonic O. kenojei, characterized by the inward growth of the perichondrium into the cartilage element, potentially linked to the morphogenesis of the skate's pectoral fins. Additionally, this study provides a set of open-source morphological data for O. kenojei, which will serve as a valuable reference for marine animal conservation and evolutionary developmental biology.

Wild populations of cartilaginous fish (sharks, skates, rays, and chimaeras) are encountering challenges. Here, we are unveiling genomic data and behavioral ecological records of Okamejei kenojei, a species listed in the IUCN Red List of Threatened Species, aiming to offer insights into the conservation and environmental adaptability of cartilaginous fish.

The role of the DMRT family in male sex determination and differentiation is significant, but its regulatory role in spotted knifejaw with Y fusion chromosomes remains unclear. Through genome-wide scanning, transcriptome analysis, qPCR, FISH, and RNA interference (RNAi), we investigated the DMRT family and the dmrt1-based sex regulation network. Seven DMRTs were identified (DMRT1/2 (2a,2b)/6, DMRT4/5, DMRT3), and dmrt gene dispersion among chromosomes is possibly driven by three whole-genome duplications. Transcriptome analysis enriched genes were associated with sex regulation and constructed a network associated with dmrt1. qPCR and FISH results showed the expression dimorphism of sex-related genes in dmrt-related regulatory networks. RNAi experiments indicated a distinct sex regulation mode in spotted knifejaw. Dmrt1 knockdown upregulated male-related genes (sox9a, sox9b, dmrt1, amh, amhr2) and hsd11b2 expression, which is critical for androgen synthesis. Amhr2 is located on the heterozygous chromosome (Y) and is specifically localized in primary spermatocytes, and is extremely upregulated after dmrt1 knockdown which suggested besides the important role of dmrt1 in male differentiation, the amhr2 along with amhr2/amh system, also play important regulatory roles in maintaining high expression of the hsd11b2 and male differentiation. This study aims to further investigate sex regulatory mechanisms in species with fusion chromosomes.

Background The use of sex-specific molecular markers has become a prominent method in enhancing fish production and economic value, as well as providing a foundation for understanding the complex molecular mechanisms involved in fish sex determination. Over the past decades, research on male and female sex identification has predominantly employed molecular biology methodologies such as restriction fragment length polymorphism, random amplification of polymorphic DNA, simple sequence repeat, and amplified fragment length polymorphism. The emergence of high-throughput sequencing technologies, particularly Illumina, has led to the utilization of single nucleotide polymorphism and insertion/deletion variants as significant molecular markers for investigating sex identification in fish. The advancement of sex-controlled breeding encounters numerous challenges, including the inefficiency of current methods, intricate experimental protocols, high costs of development, elevated rates of false positives, marker instability, and cumbersome field-testing procedures. Nevertheless, the emergence and swift progress of PacBio high-throughput sequencing technology, characterized by its long-read output capabilities, offers novel opportunities to overcome these obstacles. Findings Utilizing male/female assembled genome information in conjunction with short-read sequencing data survey and long-read PacBio sequencing data, a catalog of large-segment (>100 bp) insertion/deletion genetic variants was generated through a genome-wide variant site-scanning approach with bidirectional comparisons. The sequence tagging sites were ranked based on the long-read depth of the insertion/deletion site, with markers exhibiting lower long-read depth being considered more effective for large-segment deletion variants. Subsequently, a catalog of bulk primers and simulated PCR for the male/female variant loci was developed, incorporating primer design for the target region and electronic PCR (e-PCR) technology. The Japanese parrotfish (Oplegnathus fasciatus), belonging to the Oplegnathidae family within the Centrarchiformes order, holds significant economic value as a rocky reef fish indigenous to East Asia. The criteria for rapid identification of male and female differences in Japanese parrotfish were established through agarose gel electrophoresis, which revealed 2 amplified bands for males and 1 amplified band for females. A high-throughput identification catalog of sex-specific markers was then constructed using this method, resulting in the identification of 3,639 (2,786 INS/853 DEL, female as reference) and 3,672 (2,876 INS/833 DEL, male as reference) markers in conjunction with 1,021 and 894 high-quality genetic sex identification markers, respectively. Sixteen differential loci were randomly chosen from the catalog for validation, with 11 of them meeting the criteria for male/female distinctions. The implementation of cost-effective and efficient technological processes would facilitate the rapid advancement of genetic breeding through expediting the high-throughput development of sex genetic markers for various species. Conclusions Our study utilized assembled genome information from male and female individuals obtained from PacBio, in addition to data from short-read sequencing data survey and long-read PacBio sequencing data. We extensively employed genome-wide variant site scanning and identification, high-throughput primer design of target regions, and e-PCR batch amplification, along with statistical analysis and ranking of the long-read depth of the variant sites. Through this integrated approach, we successfully compiled a catalog of large insertion/deletion sites (>100 bp) in both male and female Japanese parrotfish.

Spotted knifejaw (Oplegnathus punctatus), one of the most valuable mariculture species, grows with significant sexual dimorphism, with males growing significantly faster than females. O. punctatus not only has excellent growth characteristics and high food value, but also shows high economic value in aquaculture, which has become a hotspot in the field of aquaculture. The current insufficiency of sex marker identification in O. punctatus restricts the process of its unisexual breeding. Rapid identification of sex will help to study the mechanisms of sex determination and accelerate the development of sex-controlled breeding. With the completion of the sequencing of the male and female genomes of O. punctatus, the efficient and precise development of genetic sex markers has been made possible. In this study, we used genome-wide information combined with molecular biology techniques from marker sequences to further establish a rapid method for DNA insertion variant detection in the intron of O. punctatus erc2 gene, which can be used to rapidly, accurately, and efficiently identify whether DNA insertion occurs in the intron of O. punctatus erc2 gene to be detected, and to identify the sex of O. punctatus to be detected. It could also be distinguished by agarose gel electrophoresis, which would shorten the time for accurate identification and improves the detection efficiency. Homozygous comparison of male and female individuals showed that the length of the DNA fragment of the erc2 gene was 239 bp on chromosome X1 and 1173 bp on chromosome Y. It can therefore be inferred that a 934 bp insertion fragment exists on the Y chromosome. The PCR amplification results showed that two DNA fragments of 1173 bp and 239 bp could be amplified in male O. punctatus, and the 1173 bp fragment was a marker fragment specific to the variant intron erc2 gene, while only a single DNA fragment of 239 bp was amplified in female O. punctatus. It has important significance and application value in the study of neurotransmitter transmission and environmental adaptability of female and male fish based on erc2 gene, as well as the identification of male and female sex, the preparation of high male fry, and family breeding.

Marine habitats and ecosystems are increasingly being impacted by global climate change and the global spread of captive breeding. In this study, we focused on five typical Trachinotus species (Trachinotus anak, Trachinotus blochii, Trachinotus mookalee, Trachinotus goreenisi, Trachinotus ovatus) as research subjects. We utilized species distribution models and ecological niche models to predict the present and future potential distribution of these species, as well as to assess ecological niche overlap and evaluate the early warning of invasion by Trachinotus species. T. ovatus stands out with its broad distribution range and high adaptability to different environments. It occupies 1.114% of medium-high suitable areas, spanning 100,147 km2. Our predictions also suggest that T. ovatus would undergo a significant expansion (approximately 55% of the total area) under both past and future environmental scenarios, demonstrating a higher tolerance and adaptability to changes in ambient temperatures. It can be discerned that T. ovatus exhibits strong environmental adaptability, which may potentially lead to biological invasion along the southeastern coast of China. The T. anak, on the other hand, showed a higher expansion trend under high carbon dioxide concentrations (RCP8.5), indicating a certain convergence with carbon dioxide concentration. Our models showed that under future climatic conditions, T. ovatus would become the dominant species, with increased competition with T. mookalee and decreased competition with T. goreenisi, T. mookalee, and T. anak. Based on our findings and the net-pen culture mode of T. ovatus, we identified the hotspot habitat of T. ovatus to be located in the Indo-Pacific convergence zone. However, there is a possibility of an expansion trend towards the southeast coast of China in the future. Therefore, it is crucial to provide an early warning for the potential biological invasion of T. ovatus.