Abstract To evaluate the aquaculture potential and developmental characteristics of the holobenthic octopus Amphioctopus fangsiao, we conducted artificial breeding and continuous rearing of Amphioctopus fangsiao from hatching to 150 days post‐hatching (dph) under laboratory conditions using broodstock collected from Fujian, China. The body weight increased from 0.156 ± 0.004 g at 1 dph to 42.343 ± 8.243 g at 150 dph, and the mantle length increased from 0.53 ± 0.02 cm to 3.93 ± 0.76 cm. The growth showed stage‐dependent patterns, with length‐related traits following logistic trends, while the body weight increased continuously without a clear asymptotic phase. Morphological and behavioral changes were also documented, including an increase in the sucker number from 26 to 30 at hatching to 110 at 150 dph. The species‐specialized golden ring at the web base appeared at around 25 dph and darkened with stimulation, while chromatophores expanded across the body to enhance camouflage. This study provides the first comprehensive dataset on A. fangsiao juvenile development. Its benthic hatching, relatively short incubation period, and stable survival highlight its aquaculture potential in East Asia.

Thamnaconus septentrionalis is an economically important marine aquaculture species in China. However, the acceptance rate of formulated feeds in commercial farming is only 30-40%, substantially lower than the 80-90% achieved with fresh feeds, which severely constrains the intensive development of this industry. The gut microbiota-mediated regulatory mechanisms underlying the effects of different feed types on growth performance remain unclear, limiting the precise development of efficient formulated feeds. This study established four feed types (commercial pellet feed K, custom-formulated feed P, frozen shrimp X, and fresh fish meat Y) through a 60-day feeding trial. Growth performance data, 16S rRNA sequencing, and untargeted metabolomics were analyzed. Random Forest-Partial Least Squares Regression models were employed to identify key microbial-metabolite features. Results indicated that the Y group exhibited the optimal feed conversion ratio (1.14), with intestinal Firmicutes abundance (45.3%) significantly higher than the K group (28.5%). Short-chain fatty acid levels increased by more than 350-fold, enriching short-chain fatty acid-producing bacteria such as Lactobacillus and Faecalibacterium. The P group, formulated with high fishmeal content (40%), achieved performance levels comparable to the Y group across most indicators. Machine learning models identified key microbial-metabolite features predicting growth performance, providing a multi-omics framework for developing efficient formulated feeds for marine carnivorous fish.

Microbiota play critical roles in the early development and health of marine invertebrates, yet microbial transmission and assembly across life stages remain poorly understood in cephalopods. The golden cuttlefish (Sepia esculenta), an important cephalopod in East Asia, suffers high larval mortality, potentially linked to microbiome instability. Here, we investigated vertical microbial transmission, stage-specific microbial succession, and functional roles of core microbiota during early development of S. esculenta. Using high-throughput 16S rRNA sequencing and culture-based methods, we profiled the microbiota across maternal tissues, as well as embryonic stages and post-hatching larvae (n = 79). Two vertically transmitted core genera, Vibrio and Pseudomonas, persisted from maternal organs to offspring and met prevalence and abundance thresholds (NorCI > 0.1). Stage-specific microbial shifts were also observed, with Aureisphaera dominating early embryonic stages and Mycoplasma, Acinetobacter, and Croceibacter emerging after hatching. Functional predictions revealed enrichment of redox-related pathways in embryos and metabolism-associated functions in larvae. Source tracking demonstrated organ-specific microbial transmission, with skin microbiota and environmental inputs. Culture-based isolation successfully retrieved 176 ASVs and improved taxonomic resolution for 92% of them. Three isolates, Bacillus, Pseudoalteromonas, and Sulfitobacter spp., exhibited antagonistic activity against Vibrio tubiashii, suggesting potential probiotic applications. Overall, our results demonstrate that early-life microbiome establishment in S. esculenta involves both maternal inheritance and stage-specific acquisition, providing insights for microbiome-informed strategies to enhance larval health in cephalopod aquaculture.

Thamnaconus modestus (black scraper) is an economically important fish species in Chinese coastal fisheries, yet its pronounced fishy off-odor, primarily attributed to sulfur-containing compounds and trimethylamine (TMA), severely limits consumer acceptance and product diversification. However, a systematic investigation into how different thermal processing methods affect its volatile flavor profile is lacking. This study employed an integrated multi-instrumental flavoromics platform combining sensory evaluation, electronic nose (E-nose), electronic tongue (E-tongue), gas chromatography–ion mobility spectrometry (GC-IMS), and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC-MS), coupled with chemometric analysis, to systematically characterize the aroma variations of T. modestus subjected to steaming, boiling, deep-frying, and roasting treatments compared with raw samples. A total of 62 (GC-IMS) and 129 (GC-MS) volatile compounds were identified, from which 78 characteristic markers (VIP > 1) and 45 key odorants (OAV ≥ 1) were screened. Thermal processing markedly reduced sulfur-containing compounds and TMA concentrations (raw >> steamed ≈ boiled >> deep-fried > roasted) while promoting lipid oxidation- and Maillard reaction-derived aldehydes and furans. Two distinct flavor modulation patterns were revealed: moist-heat methods (steaming, boiling) generated grassy/fatty notes through moderate lipid oxidation, whereas dry-heat methods (deep-frying, roasting) produced characteristic roasted/nutty notes via synergistic activation of Strecker degradation and Maillard reaction. These findings provide scientific evidence for precise flavor quality control and diversified processing optimization of T. modestus products.

The intestinal microbiota is instrumental in the nutritional absorption,immune regulation,and overall health of aquatic animals.However,limited information exists on the gut microbiota of economically important marine fish such as greenfin horse-faced filefish(Thamnaconus septentrionalis),especially across different developmental time points.Understanding microbiota succession in this species is crucial for improving larval rearing success and optimizing feed strategies. This study systematically investigated the temporal changes and community structure of the intestinal microbiota of T septentrionalis larvae and juveniles at eight representative developmental stages(G0-G50),from fertilized eggs to advanced juvenile stages.The primary objective of this study was to explore the dynamic succession of the gut microbiota and evaluate its relationships with host age,physiological state,and feed transitions(rotifer,Artemia nauplii,and frozen Artemia).We also aimed to identify the dominant and stage-specific bacterial taxa associated with different gut ecological environments during development.High-throughput 16S rRNA gene sequencing was performed on 24 gut samples at eight time points.Alpha diversity was assessed using Chao1 and Shannon indices to quantify richness and diversity.Beta diversity analysis,including non-metric multidimensional scaling and unweighted UniFrac distances,was used to evaluate community dissimilarities across stages.Linear discriminant analysis effect size(LEfSe)was employed to identify significantly enriched bacterial taxa at different stages.In addition,heat maps and cluster analyses were used to visualize the taxonomic shifts and abundance gradients of the key genera.The results revealed that the gut microbial community of T.septentrionalis underwent distinct compositional shifts during development and exhibited a phased and directed successional pattern.Alpha diversity indices showed that microbial richness was the lowest in the G0 stage(fertilized eggs),characterized by sparse colonization,mostly originating from the egg surface and surrounding water.Following the initiation of exogenous feeding at G1(rotifer ingestion),both the Chao1 and Shannon indices increased sharply,peaking at G3.This increase corresponded to microbial input from live feeds.Diversity began to fluctuate during the G9-G30 stages and gradually stabilized by G40-G50(frozen Artemia stage),suggesting the establishment of a selective and stable gut microenvironment.Beta diversity analysis further supported these findings.The samples from G0 were clearly separated from those from other stages,reflecting a unique early stage microbial signature.A transitional shift was observed from G3 to G30,and samples from G40 to G50 clustered more closely,indicating microbiota convergence and ecological stabilization during the later stages.These trends align with previous findings in other marine fish species and emphasize the interaction between gut microbiota and host development.At the genus level,the dominant bacterial taxa changed substantially during development.At G0,Vibrio and Tenacibaculum were dominant and likely originated from the environmental or egg-associated communities.At G1-G9,genera such as Acinetobacter,Cupriavidus,and Rubritalea increased in relative abundance,indicating microbial adaptation to rotifer ingestion and environmental changes in the gut.At G30,Cupriavidus,Pseudobacteriovorax,and Legionella were significantly enriched,suggesting a strong selection pressure from Artemia nauplii and associated metabolites.At G50,Photobacterium became the predominant genus(up to 63.8％relative abundance),likely because of the prolonged feeding of frozen Artemia and altered gut nutrient availability.The enrichment of species,such as P.aphoticum and P.damselae,may indicate potential health risks related to pathogenicity,as reported in other marine fish.LEfSe analysis confirmed the presence of stage-specific genera.Tenacibaculum was a biomarker for G0,Epibacterium and Xanthomarina for G3,Lactobacillus and Streptococcus for G9,and Massilia and Pseudobacteriovorax were indicators for G20-G30.These findings suggest that different feeding regimes and developmental stages exert selective pressures that shape the unique microbial niches within the gut.The dynamic pattern of the appearance and disappearance of key taxa implies an adaptive microbial response to host nutritional status and gut maturation.This study provides the first comprehensive profile of intestinal microbial succession in T.septentrionalis during its early ontogeny.These results highlight the essential role of diet and age in shaping gut microbial ecology.Maintaining microbial diversity,particularly during critical feed transitions,enhances host resistance and survival.Moreover,insights into the dominant and beneficial taxa lay the groundwork for future development of probiotic or microbiome-targeted functional feeds.

To evaluate the aquaculture potential of Amphioctopus kagoshimensis, we investigated the reproductive biology, embryonic development, and early paralarval morphology of Amphioctopus kagoshimensis under controlled laboratory conditions. Each adult specimen collected from the coastal waters of Fujian Province spawned approximately 4000–5000 eggs (mean ± SD: 4375 ± 478 eggs), with an overall hatching rate of 75% ± 10% (n = 2). Embryonic development lasted approximately 30 days at 22.0–24.5 °C and followed a classical 20-stage pattern. Hatchlings measured an average mantle length of 1.4 ± 0.1 mm and exhibited a merobenthic strategy, characterized by planktonic paralarvae with progressive morphological differentiation. The chromatophores appeared progressively on the head, mantle, arms, and funnel, with numbers increasing from 5 to 23 per arm by 30 days post-hatching. Paralarvae demonstrated active swimming, feeding behavior, and arm sucker development during rearing. By day 30, mantle length reached 2.5 mm, with significant growth in arm length and behavioral complexity. Its relatively small adult size (mantle length 8 cm), a moderate egg size (2.6 mm), fecundity and successful artificial incubation and 30-day paralarvae seedling suggested it may be a suitable model species for developmental studies and potential candidate for merobenthic octopod aquaculture in East Asia.

As global extreme heat events become more frequent, aquaculture faces significant challenges due to prolonged high summer temperatures, which lead to elevated water temperatures. Investigating the physiological and biochemical responses of fish to thermal stress, as well as breeding heat-resistant varieties, are essential strategies for addressing these challenges. Thamnaconus septentrionalis is an important aquaculture species in southern China. When water temperatures exceed 30 °C during the summer, this species experiences reduced feeding, growth stagnation, and increased mortality rates. To elucidate the physiological and biochemical response mechanisms of T. septentrionalis under thermal stress, this study established a high-temperature group (30 °C) and a control group (20 °C) for a 48-h thermal stress experiment. Tissue samples were collected from the experimental fish at 0, 12, 24, and 48 h post-stress. The effects of acute thermal stress on gill tissue structure, serum biochemical indicators, liver antioxidant capacity, and liver transcriptomics were explored. The results revealed that the gill tissues of the high-temperature group exhibited slight bending of the gill filaments, terminal swelling, and cellular vacuolization, along with a tendency for adjacent gill filaments to fuse. The liver antioxidant capacity and serum biochemical indicators in the high-temperature group were significantly elevated compared to the control group (P < 0.05). Transcriptomic sequencing identified 5536 differentially expressed genes (P < 0.05), with 2639 genes upregulated and 2897 downregulated. Gene Ontology (GO) enrichment analysis indicated that differentially expressed genes were primarily associated with metabolic processes and redox reactions. KEGG pathway analysis showed significant enrichment of genes in pathways related to amino acid metabolism, carbon metabolism, and glycolysis/gluconeogenesis, with notable downregulation observed in the high-temperature group. This study provides valuable theoretical insights into the mechanisms underlying the response of T. septentrionalis to high-temperature stress, contributing to the understanding of aquaculture resilience in the face of climate change.

The high mortality rate during the benthic settlement process of Octopus sinensis paralarvae represents the primary technical bottleneck constraining the development of its aquaculture industry. The functional roles of chemical factors in this critical transitional phase are unknown. Considering the crucial role of chemosensory receptor genes in chemical factor perception, this study identified three classes of chemosensory receptor genes-Olfactory Receptors (ORs), Ionotropic Receptors (IRs), and Acetylcholine Receptors (ARs)-in both merobenthic species (O. sinensis, Octopus vulgaris) and holobenthic species (Octopus minor, Amphioctopus fangsiao). The results demonstrated that the number of chemosensory receptor genes identified in all species in this study was comparable. Tissue expression analysis revealed that IRs were widely expressed across multiple olfactionrelated organs, while the cephalopod-specific ARs were predominantly expressed in suckers and sucker epithelium. From hatching to adulthood, merobenthic paralarvae exhibited downregulation of nearly half of their chemosensory receptor genes, whereas holobenthic paralarvae showed only about 10 % gene downregulation, reflecting distinct chemosensory receptor expression patterns driven by divergent ecological adaptations between the hatchlings of these two life-history strategies. Based on the analysis of chemosensory receptor gene expression levels at different developmental stages of merobenthic paralarvae, RYamide receptor, Cholecystokinin receptor A (CCKAR), and Free fatty acid receptor 4 (FFAR4) were identified as potential key chemosensory receptor genes involved in the benthic settlement process. All three genes were functionally linked to feeding regulation, suggesting that chemical factors may regulate paralarval physiological functions related to feeding, thereby helping paralarvae conserve energy while awaiting the maturation of their nervous system and arm functionality, which would facilitate a successful transition to benthic settlement. This study laid a solid foundation for identifying key chemical factors involved in the benthic settlement process, which will contribute to breakthroughs in artificial seedling breeding techniques for O. sinensis and promote the development of its aquaculture industry.

Cephalopods,which have a rapid growth rate and short life cycle,are regarded as an important marine fishing resource.Sepioteuthis lessoniana is among the most widely distributed species in the Loliginidae family in the Indo-Westem Pacific Ocean.Its meat is delicious and nutritious.It is widespread in the East China Sea,South China Sea,and other marine areas in China,and it is considered an important local marine resource.In this study,the ultrastructure of the oviducal gland of S.lessoniana was investigated for the first time via anatomical dissection,tissue sectioning,and electron microscope projection.The external morphology and internal structure of the gland were clearly described,as well as the role of the oviduct gland in the reproductive activities of cephalopods.In this experiment,all the samples were collected from the open ocean,with the samples of wild S.lessoniana coming from marine areas in Fujian Province.The body surfaces of the samples were healthy and undamaged,with an average mantle length of(17.5±6.4)cm and an average body weight of(392.0±76.0)g.The samples were dissected using standard anatomical methods,and the glandular characteristics were recorded.The oviducal gland was dissected with a scalpel for tissue sectioning and preserved for electron microscope projection and observation.The experimental results showed that S.lessoniana had a single oviducal gland,which was located on the right side of its abdominal cavity.The sexually mature gland was milky white overall,with brownish-yellow pigmentation near the inner shell.The oviducal gland was enveloped in a transparent membrane,and regular gaps were visible.The gland consisted of three parts:the proximal oviducal gland,the distal oviducal gland,and the transparent valve.The proximal oviducal gland was infundibular and connected with the hyaline oviduct.The distal oviducal gland was cylindrically tapering,and a single mature egg was observed inside.The transparent valve was at the end of the gland,also known as the valve.The microstructure of the oviducal gland was observed via a microscope.The gland was composed of a glandular wall,lamellar,and muscle tissue.The glandular wall tissue was composed of adventitia,loose connective tissue,and a small amount of muscle tissue,blood vessels,and ducts that were scattered in the connective tissue.The transparent valve was composed of columnar epithelial cells and muscle tissue.A small number of water-droplet goblet cells were dispersed between the epithelial cells,while a large number of cilia were generated on the exterior.The lamellar was attached to the glandular wall tissue and distributed in layers within the gland;it was mainly composed of ciliated columnar epithelium and support cells.When the oviducal gland was at various development stages,the cell types of the lamellar and the size of the intercellular space within the leaflet were different.When the gland was immature,the lobe had a regular shape,with more connective tissue in the center and a single layer of columnar epithelial cells on each side.When the gland was about to mature,the connective tissue increased,the number of columnar epithelial cells decreased,and a large number of mucous acmus were simultaneously generated.After the glands matured and spawned,the amount of connective tissue decreased,the columnar epithelial cells disappeared,the mucous acinus ruptured,and the secretory leaflets were filled with secretory substances.The individual oviduct gland secretory cells of S.lessoniana were large and contained many closely arranged mucus granules,which were round or oval in shape.The cytoplasm contained many organelles,such as the endoplasmic reticulum,mitochondria,and Golgi apparatus.In addition,secretory cells were continuously distributed outside the cell with cilia and numerous secretory granules.The nucleus of the muscle cells in the hyaline valve was irregular,and a substantial number of myofilaments,collagen fibers,and capillaries could be seen around it.The oviducal gland is an important gland in the reproductive system of female cephalopods.The morphological characteristics of oviducal glands,such as the number,shape,size,and presence or absence of pigmentation,are some of the distinguishing characteristics between different cephalopod species.The tissue structure and cell types of the cephalopod oviducal glands changed with the growth of individuals.The changes in oviducal glands in S.lessoniana were similar to those in Loligo forbesi.The secretory lobes successively generated an increasing number of mucous acini and secretory substances as cell types shifted.These secreted substances had multiple functions,such as attracting sperm during the sperm-egg hatching process,expanding the chorionic membrane,forming the vitelline space,and regulating the osmotic pressure between the fertilized egg and the ambient seawater.However,the oviducal glands of the orders Cuttlefish and Liliformes differ from those of the order Occarpus,whose oviducal glands had the function of storing sperm.It is concluded that the oviducal gland primarily plays a secretory function in the reproductive activities of cephalopods and that its secretory material forms the second layer of the egg membrane of fertilized eggs,ensuring the normal hatching of fertilized eggs.

The East Asian common octopus (Octopus sinensis) is an economically important species among cephalopods. This species exhibits a strict dioecious and allogamous reproductive strategy, along with a phenotypic sexual dimorphism, where the third right arm differentiates into hectocotylus in males. However, our understanding of the molecular mechanisms that underlie sex determination and differentiation in this species remains limited. In the present study, we surveyed gene-expression profiles in the immature male and female gonads of O. sinensis based on the RNA-seq, and a total of 47.83 Gb of high-quality data were generated. Compared with the testis, we identified 8302 differentially expressed genes (DEGs) in the ovary, of which 4459 genes were up-regulated and 3843 genes were down-regulated. Based on the GO enrichment, many GO terms related to sex differentiation were identified, such as sex differentiation (GO: 0007548), sexual reproduction (GO: 0019953) and male sex differentiation (GO: 0046661). A KEGG classification analysis identified three conserved signaling pathways that related to sex differentiation, including the Wnt signaling pathway, TGF-β signaling pathway and Notch signaling pathway. Additionally, 21 sex-related DEGs were selected, of which 13 DEGs were male-biased, including Dmrt1, Foxn5, Foxj1, Sox30, etc., and 8 DEGs were female-biased, including Sox14, Nanos3, β-tubulin, Suh, etc. Ten DEGs were used to verify the expression patterns in the testis and ovary using the RT-qPCR method, and the results showed that the expression level shown by RT-qPCR was consistent with that from the RNA-seq, which confirmed the reliability of the transcriptome data. The results presented in this study will not only contribute to our understanding of sex-formation mechanisms in O. sinensis but also provide the foundational information for further investigating the molecular mechanisms that underline its gonadal development and facilitate the sustainable development of octopus artificial breeding.

Fish skin is a multipurpose tissue with important functions—protection, perception, and hormone metabolism—in the fish body. As a byproduct of fish processing, it can be used as a material for extracting collagen, making leather, and related pathological research. However, there have been few reports on the tissue structure of fish skin. This study aimed to analyze the structural characteristics of Thamnaconus septentrionalis fish skin in order to provide a reference for the utilization of its resources. Six T. septentrionalis samples were selected and their skins were observed using frozen sectioning, skeletal, hematoxylin & eosin (H & E), Periodic acid-Schiff (PAS), Masson, Van Gieson (VG) staining, and scanning electron microscopy. The images obtained by slice scanning were analyzed using SlideViewer (3DHISTECH), ImageJ, and Photoshop software. The SEM images were analyzed using ImageJ and Photoshop software. SPSS25.0 software was used to analyze the data of epidermal and squamous layers, conical bone bulge, basal layer, and dermis thicknesses. The results showed that the histological structure of the skin comprised four parts: epidermis, scale layer, dermis, and subcutaneous tissue. The thickness of the epidermal layer was (26.81±7.48) μm. This layer was mainly composed of epithelial and basal cells but also contained a large number of mucus cells. The scale layer consisted of the spine of conical bone and a substrate. The thickness of this layer was (22.49±5.19) μm, and there were two to four rows of the spine of conical bone with different diameters, different bending degrees at the top, and a height of (257.13±10.41) μm unevenly distributed on the base plate. The average thickness of the dermis was (176.97±21.11) μm, and the dermis thickness of the head was lower than that of the middle part of the body, but higher than that of the tail, mainly composed of collagen fiber. The subcutaneous tissue layer was mainly comprised of collagen fibers and non-fibrous stroma. In this study, the histological pattern of the skin of T. septentrionalis was mapped according to its characteristics, providing valuable information for fish skin resource usage.

The aim of this work is to develop a utilization of waste Thamnaconus septentrionalis skin resources. For this purpose, the tissue structure of T. septentrionalis skin and the basic nutrient composition were determined, and two types of fish leather: Chrome-free (NC) and Chrome (C) tanned fish leather were prepared in this study. The results obtained showed that leather fibers were more uniformly distributed and better dispersed after tanning with chrome–free tanning agents, and the mechanical properties of NC–fish leather were nearly identical to those of C–fish leather. The shrinkage temperatures of NC– and C–fish leather, were 80.6 °C ± 0.6 °C and 94.5 °C ± 0.7 °C, respectively, which were consistent with the TG thermal stability results (306 °C < 320 °C). All results confirm the feasibility of preparing chrome–free fish leather from T. septentrionalis skin, which would promote sustainability by reducing environmental pollution, conserving resources, and supporting the development of green industries.

The morphological characteristics,ecological habits,and physiological structures of fish vary rapidly in the early growth and development stage.Understanding the changes in the postembryonic early development morphology of organs or tissues could provide basic information for the classification or identification of fish and the investigation or utilization of early resources.Morphological characteristic observation is one of the most commonly used methods.The existing studies on the early development of a certain trait in the late larval and juvenile stage are unclear.Most of the digital images are side views,resulting in a lack of dorsal views,ventral views,or local images,which is not conducive to the understanding of larval and juvenile.In this study,the variations in observable,measurable,and countable traits in postembryonic early development of Thamnaconus septentrionalis were explored using optical microscopy and stereomicroscopy.The observable traits included the developmental changes of yolk sac,scales,and notochord curvature.The measurable traits included the growth changes of total length,body length,body height,and oral fissure.The countable characters included the number of fins in the second dorsal fin,anal fin,caudal fin,and the number of pterygiophore.The results showed that at(23.0±1.0)℃,the newly hatched larvae moved up and down in the water,with a phenomenon of convergent clustering under light irradiation;the pectoral fin appeared at 1 d,and the heart rate was approximately 50 beats/min;the optic capsule was completely black,the maxillar appeared,the oral fissure extended below the eyes,the yolk sac disappeared,and the first dorsal fin base appeared at 4 d;the girdle was single and colorless and began from the front edge of the belly,the oil globule disappeared,and the pelvic fin base appeared at 7 d;the first dorsal fin base and pelvic fin base broke membrane at 8 d;the first dorsal fin and pelvic fin were significantly longer than before,transparent rounded scales were observed at 9 d;swimming ability was improved,indicated by hovering back and forth gnawing pool wall,transversally conical barbs appeared at the base of the first dorsal fin at 11 d;the swim bladder and postcleithrum on both sides of the belly were clearly visible at 12 d;the second dorsal fin and anal fin pterygiophore appeared at 14 d,the second dorsal fin pterygiophore spans seven sarcomeres and the anal fin pterygiophore spans six sarcomeres.There are 10～12 melanin masses in the second dorsal fin and 5～6 in the anal fin,the conical teeth appeared on the upper and lower jaws at 16 d;the second dorsal fin and anal fin were differentiated at 19 d;the swim bladder fills about 25％of the abdominal cavity;notochord curves upward clearly and the stalk of caudal fin came out at 20 d;the fin strips of the second dorsal fin,anal fin,and caudal fin were well-developed at 24 d;the open mouth was round and changed from swallowing to sucking at 30 d,and the rainbow cells were colorful and the body surface near the gill was the most dense;the abdominal cavity has a strong metallic texture,the hard spine of the pelvic fin was degraded,close to the girdle at 39 d;4～5 black bands were arranged regularly on the body,and the lateral line was consistent with the vertebral column at 50 d.The R2 values of the curve equations of measurable traits were all greater than 0.90.The height of the first dorsal fin increased exponentially 4～30 d.The visual sac increased linearly from 0～11 d to 11～20 d,and the increment of 0～11 d was less than that of 11～20 d,while the increment of 21～30 d was exponential.The oral fissure in 4～13 d and 22～30 d increased linearly,while that in 13～22 d decreased linearly.The total length,body length,and body height increased linearly before the inflection point and exponentially after the inflection point,which was concentrated in 19～23 d.The number of fin pterygiophore of the second dorsal fin was 31～36,while that in the anal fin was 33～35.The number of pectoral fins and caudal fins were 15～18 and 12,respectively.In conclusion,metamorphosis occurs in the postembryonic early development of T.septentrionalis,showing an allometric growth pattern,with a slow linear growth in the rotifer-feeding stage and a fast exponential growth in the artemia-feeding stage.The changes in the first dorsal fin and pelvic fin were correlated with age in days.The changes in the second dorsal and anal fins were correlated with the total length.This study enriches the early biological theory of T.septentrionalis and provides basic data for the investigation or utilization of its seedling breeding and resources.The partial enlarged detail is helpful for scholars to further understand the larval or juvenile fish and perform deep research.

The common long-arm octopus (Octopus minor) is a commercially important aquaculture species in East Asia, and the male octopus grows faster than the female ones, while the information about sex-regulating mechanisms in octopuses is limited. Therefore, gonadal transcriptome sequencing was performed in O. minor to reveal the molecular mechanisms of sex regulation in cephalopods. Based on the sexuality and gonad development stage, 4 groups of 12 gonad tissues were sampled, and 11 libraries were retained for bioinformatics analysis. A total of 263,749,727 clean reads were obtained. The percentage of clean reads mapped to the O. minor reference genome ranged from 77.20% to 90.59%. A total of 3936 differentially expressed genes (DEGs) were obtained between ovarian and testicular libraries by Venn diagram analysis, including 855 ovarian up-regulated and 3081 testicular up-regulated genes. Four unigenes (transcription factor Sox-8, fermentation-1, forkhead box protein L2, and ribosomal protein large 24) and one pathway (ECM-receptor interaction) were screened to be candidate molecular markers for sex determination. The reliability and accuracy of our analysis were validated via quantitative real-time PCR in 10 randomly selected DEGs. The results of our study enhanced our understanding of the molecular mechanism underlying sex determination and potentially helped to screen the bio-markers for O. minor in different sexes.

Thamnaconus septentrionali has excellent breeding characteristics,is omnivorous,easy to domesticate,is especially suitable for netting,cleans the netting,and effectively reduces labor-costs.T.septentrionali is available in various sizes and is raised in the market at 100 g.Under water temperature of 18-25℃,after 5-6 months of breeding,it reaches commercial size.As the Yellow Sea and Bohai Sea are cold in winter,a suitable breeding cycle for green fins is from May to November annually.Under natural conditions,the spawning period of T.septentrionali in the Yellow Sea and Bohai Sea is from early May to early June,making good use of the suitable breeding cycle of net box culture.Therefore,reproductive regulation is required to advance the reproductive period of T.septentrionali.Previous studies have primarily focused on the expression and functional analysis of individual genes.In contrast,no studies exist on the overall expression analysis of gonad-related genes based on histology.Herein,we conducted the first transcriptome sequencing analysis of the spermatophores and ovaries of T.septentrionali using an Illumina high-throughput sequencing platform.Overall,165,981,523 raw reads were sequenced from the cDNA,and 161,234,846 clean reads were obtained after quality control.The Q20 of each sample was＞98.43%,Q30 was＞95.25%,and GC content of the sample bases was greater than 52.31%.Our findings indicate that the sequencing data are accurate,of good quality,and were used for subsequent analyses.The obtained unigenes were annotated in the NR(NCBI non-redundant protein sequences),NT(NCBI nucleotide sequences),PFAM(protein family),KOG(euKaryotic Ortholog Groups),SwissProt(a manually annotated and reviewed protein sequence database),GO(Gene Ontology),and KO(KEGG Orthology)databases,and 24,009,35,057,18,453,26,971,30,294,11,420,and 21,613 unigenes were annotated,respectively.The KEGG annotation results were divided into five major categories:organic systems,with 2,115 genes in nine pathways;metabolism,with 1,444 genes in 12 pathways;environmental information processing,with 1,200 genes in three pathways;and genetic information processing,with 1,128 genes in four pathways.Environmental information processing(1,200 genes in three pathways),genetic information processing(1,128 genes in four pathways),and cellular processes(1,128 genes in four pathways).The number of genes enriched in cellular process-related pathways was 927 distributed in four related pathways.The signal transduction pathway was the most annotated KEGG pathway with 804 genes.The experiment used 24,546 unigenes annotated in the KOG database,which were then classified into 26 categories based on their function.The largest number of unigenes were annotated in the signal transduction mechanism category(5,411),followed by the general function prediction-only category(4,252 unigenes),and posttranslational modification,protein folding and chaperone category(1,713 unigenes).Unigene posttranslational modification,protein turnover,chaperones;transcription,1,613;and other related functions.There were 18,954 differentially expressed genes(DEGs)in the spermatophore and ovary transcriptomes of the T.septentrionali,with 11,265 genes up-regulated and 7,689 down-regulated in the ovary relative to the spermatophore.The GO functional enrichment analysis revealed that DEGs were most enriched in the cellular component of biological processes,intracellular component of the cellular component subclass,and nucleic acid binding of the molecular functional subclass.GO analysis of the DEGs in males and females provided a partial list of genes associated with the reproductive process(GO:0022414),sexual reproduction(GO:0019953),gamete formation(GO:0007276,),sex differentiation(GO:0007548),and gonad development(GO:00084060).To further characterize the specific functions of the DEGs in the spermatophores and ovaries of T.septentrionali,the enriched signaling pathways were further analyzed using the KEGG database.In total,154 KEGG pathways were included,of which the top 30 were selected.The functional pathways with the highest number of expressed genes were closely associated with gonadal sex differentiation and development,including the insulin signaling pathway,steroid hormone biosynthesis,FoxO signaling pathway,M-TOR signaling pathway,and progesterone-mediated oocyte maturation.Among these,the FoxO signaling pathway regulatory genes are expressed in multiple processes,such as cell cycle control,apoptosis,and gluconeogenesis.The insulin signaling pathway plays an important role in regulating developmental,metabolic,and lifespan physiological processes,and the insulin signaling pathway is involved in gonadal development and maturation.Nine DEGs,bmp2,sox3,figla,hsd17b1,cyp19a,cyp17,foxl2,star,and amh,were selected for real-time fluorescence quantitative PCR(qRT-PCR)validation.The qPCR results were consistent with those of RNA-seq analysis.GO and KEGG enrichment results were analyzed and revealed that amh,cyp17,and star are imperative in male spermatogenesis of T.septentrionali;bmp2,foxl2,cyp19a,figla,and hsd17b1 are essential in female oogenesis and ovarian steroidogenesis.By comparing the transcriptome expression differences between the spermatophore and ovary of T.septentrionali,we elucidated the gene expression characteristics of the spermatophore and ovary,laying the foundation for future research on the mechanism of reproductive development of T.septentrionali and providing theoretical support for optimizing reproductive regulation techniques.

Heat shock proteins (HSPs) are a class of highly conserved proteins that play an important role in biological responses to various environmental stresses. The mariculture of Thamnaconus septentrionalis, a burgeoning aquaculture species in China, frequently encounters stressors such as extreme temperatures, salinity variations, and elevated ammonia levels. However, systematic identification and analysis of the HSP70 and HSP90 gene families in T. septentrionalis remain unexplored. This study conducted the first genome-wide identification of 12 HSP70 and 4 HSP90 genes in T. septentrionalis, followed by a comprehensive analysis including phylogenetics, gene structure, conserved domains, chromosomal localization, and expression profiling. Expression analysis from RNA-seq data across various tissues and developmental stages revealed predominant expression in muscle, spleen, and liver, with the highest expression found during the tailbud stage, followed by the gastrula, neurula, and juvenile stages. Under abiotic stress, most HSP70 and HSP90 genes were upregulated in response to high temperature, high salinity, and low salinity, notably hspa5 during thermal stress, hspa14 in high salinity, and hsp90ab1 under low salinity conditions. Ammonia stress led to a predominance of downregulated HSP genes in the liver, particularly hspa2, while upregulation was observed in the gills, especially for hsp90b1. Quantitative real-time PCR analysis corroborated the expression levels under environmental stresses, validating their involvement in stress responses. This investigation provides insights into the molecular mechanisms of HSP70 and HSP90 in T. septentrionalis under stress, offering valuable information for future functional studies of HSPs in teleost evolution, optimizing aquaculture techniques, and developing stress-resistant strains.

以绿鳍马面鲀(Thamnaconus septentrionalis)胚胎及初孵仔鱼为实验对象,采用静水试验方法,研究Cu2+、Cd2+对绿鳍马面鲀胚胎及初孵仔鱼的毒性效应.结果表明,随着重金属溶液浓度升高,绿鳍马面鲀胚胎畸形率呈上升趋势,孵化率呈下降趋势,初孵仔鱼呈现V、S、L、U等各种畸形状态;囊胚期至神经胚、器官分化至出膜2个阶段发育时长均随Cu2+浓度的增加呈先缩短后延长趋势,2个阶段发育时长均随Cd2+浓度的增加呈延长趋势;不同Cu2+、Cd2+浓度组在2个发育阶段死亡率均随浓度增加而升高,同一浓度下,器官分化至出膜阶段胚胎死亡率低于囊胚期至神经胚阶段;初孵仔鱼存活率与重金属溶液浓度和培育时间呈反比,畸形率与溶液浓度呈正比.Cu2+、Cd2+对初孵仔鱼72 h-LC50值分别为0.063 mg·L-1和3.589 mg·L-1,其对应的 95％置信区间分别为 0.052～0.072 mg·L-1 和 3.184～3.944 mg·L-1.安全浓度分别为 0.006 mg·L-1 和 0.359 mg·L-1.本实验表明,Cu2+对绿鳍马面鲀胚胎发育及初孵仔鱼的毒性大于Cd2+.

Aquatic animals immune response to pathogenic is a hotspot and related to high-quality development of aquaculture industry and the conservation of fisheries resources. Thamnaconus modestus is an important commercial and economical species which is suffering from various pathogens but by now lack relevant research about revealing the immune response mechanism to the pathogens invasion. In the study, the polyriboinosinic polyribocytidylic acid [poly (I:C)] and Lipopolysaccharides (LPS), respective mimics of viral and bacterial in-fections, were used to demonstrate the immune response of the species via transcriptome analysis. The results showed that T. modestus had sensitive responses to the viral analog infection at 6 h and 48 h, and at 6 h, the first five major functional genes were NFKBIA, IL1B, JUN, IGH, FOS, and at 48 h, the genes were NFKBIA, IL1B, JUN, IGH, FOS. The genes IL1B, IRF3, PTGS2, THBS1 could helping the fish to fight against the bacterial infection in both the times. Similarly for the bacterial infection, the species had a sensitive response at 6 h, and the first five major functional genes were NFKBIA, JUN, FOS, L1B, GRIN2C. Our study provided an insight about the immune response mechanism of this species and demonstrated that if need for treatment of the virus and bacteria by the biotechnology, the artificial interferential time would be suggested before 6 h since the pathological features occur and the genes NFKBIA, JUN, IL1B, FOS, TRAF2, IL8, SOCS3, PTGS2 should be payed more attention.

In this study, the microstructure of an ovary was histologically observed in immature Indo-Pacific oval squid Sepioteuthis lessoniana with body weight of（210 ± 43）g and the mature ones with body weight of（430 ± 76）g and the oogenesis was divided into several stages according to the characteristics and change in each stage of the eggs in order to understand the characteristics of oogenesis in the squid. The results showed that the oogoniums were small individually and gradually increased with development and maturation. The flat follicular cells were first found and wrapped the oocytes, then a layer of elliptical follicular cells was formed outside the flat follicular cells. The double-layer follicular cells gradually rolled inward into the oocytes and formed finger-like processes which processed gradually to be connected to a network and filled the whole cell. The nucleus of the oocytes was squeezed to one side,meanwhile the flat follicular cells began to disintegrate, and a small amount of yolk material began to form in the process space. Finally, the follicular cells were completely disintegrated, and the oocyte was filled with yolk material, with the maximal size. Based on the characteristics above, the eggs of Indo-Pacific oval squid were divided into the first stage（oogonium phase）, the second stage（no follicular cell phase, single-layer follicular cell phase and double-layer follicular cell phase）, the third stage（early, middle and late phase of follicular cell proliferation）. It is suggested that the follicular cells play a role in synthesizing and secreting nutrients during oogenesis in Indo-Pacific oval squid.