ROUNDUPS

• CTP: phosphocholine cytidylyltransferase alpha (CCTα) - advances on its role and regulation in memebrane lipid biogenesis and lipid metabolism

  AI Qinghui, ZHAN Rui

  2025,49(6):069601-069601, DOI: 10.11964/jfc.20240514522

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  Phosphatidylcholine (PC) is a major component of membrane phospholipids and plays essential biological roles. The primary pathway for PC synthesis is the CDP-choline pathway, in which CTP: phosphocholine cytidylyltransferase (CCT) functions as the rate-limiting enzyme and is a key factor in maintaining PC homeostasis. CCTα, one of the major isoforms of the CCT family, is widely distributed across mammalian organs and tissues, and plays crucial roles in membrane biogenesis and lipid metabolism. Recent studies have shown that CCTα is also present in fish and exerts important regulatory functions in fish lipid metabolism. This review summarizes the functions and regulatory mechanisms of CCTα in both mammals and fish, with a focus on its roles in membrane biogenesis and lipid metabolism. Additionally, the potential of CCTα as a molecular target for regulating nutritional metabolic disorders in fish is explored, aiming to provide a theoretical implications for the healthy development of aquaculture.

• Accounting methods and influencing factors of greenhouse gas emissions in aquaculture

  LIANG Hejun, HAN Guanrong, XU jingxiang, ZHANG Jinhui, LI Canfeng, SUI Hengshou

  2025,49(6):069302-069302, DOI: 10.11964/jfc.20240114350

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  Aquaculture is an important part of aquaculture, and its greenhouse gas emissions cannot be ignored. In order to clarify the calculating methods, flux measurement, and influencing factors of carbon emissions in aquaculture ecosystems, this paper systematically reviewed and integrated relevant research on greenhouse gas emissions of aquaculture, summarized the current calculation methods of greenhouse gas emissions, including oak ridge national laboratory method, Intergovernmental Panel on Climate Change emission factor method, and life cycle assessment method, and outlined methods for measuring greenhouse gas emissions, such as inverted funnel method, eddy covariance technique, and static chamber method. In addition, this paper analyzed various factors affecting greenhouse gas emissions from the perspectives of aquaculture species, water management mode, temperature, and feed. The study found that: ① greenhouse gas emission calculating methods have not reached a consensus in the present scientific community, the calculation formulas are oversimplified, and the factors considered are not comprehensive; ② flux measurement is complex, and the measurement accuracy and efficiency need to be improved; ③ there are many factors that affect carbon emissions, and feed is the largest contributing factor to greenhouse gas emissions from quaculture, but limited studies have addressed the aquatic animal-derived metabolic carbon generated by feeding. This paper points out that relevant research currently has certain limitations, and proposes suggestions for future research on greenhouse gas emissions of aquaculture from four angles: estimation methods, factors considered, monitoring time, and N₂O emission factors, in order to provide inspiration and assistance for deeper research in the future.

PAPERS

• Molecular cloning and expression analysis of IgMH and MHCⅡβ genes in the spotted sea bass (Lateolabrax maculatus)

  LEI Lina, GAO Qian, WANG Wei, SUN Zhaosheng, LUO Zhang, LIU Qigen

  2025,49(6):069403-069403, DOI: 10.11964/jfc.20230213905

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  To gain a deeper comprehension of the adaptive immune mechanism involved in disease prevention and control of Lateolabrax maculatus, this study employed RT-PCR and RACE techniques to clone the immunoglobulin M heavy chain (IgMH) and Major histocompatibility compatibility complex β (MHCⅡ β). Additionally, real-time fluorescence quantitative PCR (qPCR) was utilized to examine the expression distribution in different tissues of spotted sea bass, along with the alterations in mRNA levels following LPS, Poly (I: C) stimulation, and Edwardia tarda infection. Finally, the expression of recombinant proteins IgMH, IgMCH_1-2, and MHCⅡ β was achieved by constructing prokaryotic recombinant expression plasmids IgMH-pET21d, IgMCH_1-2-pET21d, and MHCⅡ β-PET21d. The proteins were obtained through molecular sieve chromatography, and anti IgMH Polyclonal antibodies of L. maculatus were successfully prepared. The results indicated that the full length cDNA of IgMH and MHCⅡ β in L. maculatus were 1 977 bp and 1 242 bp, respectively. The genes IgMH and MHCⅡ β exhibit high expression in immune-related tissues, including gills, spleen, and head kidney. LPS and Poly (I:C) stimulation and delayed Edwardsiella artificially infected L. maculatus led to significant changes in the expression levels of these two genes in gill, spleen and head and kidney, indicating that both IgMH and MHCⅡ β participated in the anti-infection immune response of L. maculatus. Additionally, immunoblotting analysis demonstrated that anti-IgM Polyclonal antibodies display strong reactivity with the entire serum of L. maculatus, weak reactivity with Siniperca chuatsi, and no reactivity with Micropterus salmoides and Cienoyharyngodoni della. It is speculated that the reaction intensity reflects the genetic relationship between species. In summary, this study successfully accomplished the cloning of the complete sequences of IgMH and MHCⅡ β genes, followed by the expression of recombinant IgMH and MHCⅡ β proteins. Additionally, the production of Anti-IgM polyclonal antibody was achieved. The findings of this study provided evidence supporting the involvement of IgMH and MHCⅡ β in the immune response of L. maculatus. Furthermore, these results established a solid groundwork for future investigations on immune regulation and disease prevention and control strategies for L. maculatus.

• Genome-wide association analysis of low temperature tolerance in Nibea albiflora

  JIN Xun, LIU Bingjian, ZHU Qihui, ZHANG Wanchang, LI Wanbo, WANG Zhiyong, GAO Tianxiang, XU Dongdong

  2025,49(6):069604-069604, DOI: 10.11964/jfc.20230714075

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  Increasing temperature extremes are caused by global climate change. Extreme low temperature has caused the increase of death rate for Nibea albiflora in winter, which has seriously restricted the development of aquaculture industry. N. albiflora is one of the important mariculture fish in China. Studying the molecular mechanism of response to low temperature stress can provide theoretical basis for N. albiflora culture to cope with the challenges of extreme low temperature. In this study, 200 N. albiflora individuals were selected to low-temperature stress at 5 °C, and the survival time, weight, body length, sex and other phenotypic parameters of every individual were recorded. Then, whole genome was resequenced. A total of 3 005 715 high-quality single nucleotide polymorphism (SNPs) sites were obtained by comparing to the reference genome (NCBI GenBank number: GCA_014281875.1), and the obtained SNP sites were used for genome-wide association analysis (GWAS) using the Mixed linear model (MLM) based on EMMAX software. The results showed that the phenotypic parameters such as body weight, body length and sex were not significantly correlated with the low temperature tolerance time (P=0.834-0.013). However, 9 sites were identified on 24 chromosomes that were significantly correlated (P=1.98×10^-6- 4.61×10^-8) with the low temperature tolerance time, and a total of 13 candidate genes, such as CBL.3, STOML2.2 and SLC37A3 were annotated. Gene ontology (GO) analysis showed that the above genes were mainly enriched in the processes of immunity, defense and repair, stress and mitochondrial energy metabolism, which may be related to low temperature response of the N. albiflora. The results of this study can provide reference for the genetic improvement of low temperature tolerance.

• The role of sox9 gene in male gonadal differentiation of Pelodiscus sinensis

  LIANG Xiao, JIN Lin, LI Pan, YANG Bangsai, QIAN Guoying, GE Chutian, SUN Wei

  2025,49(6):069605-069605, DOI: 10.11964/jfc.20230914168

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  Chinese soft-shelled turtles (Pelodiscus sinensis) possess apparent sexual dimorphism on production traits, and the realization of all-male breeding is the important measure for the improvement of the industry. In this study, the highly conserved gene sox9 in vertebrate male differentiation was chosen as manipulating object, and by injecting Lentivirus-sox9-shRNA interference and overexpression vector system into embryos before sexual differentiation, we discussed the specific function of sox9 during the early testicular differentiation of P. sinensis from the level of histology and molecular study. The results of the loss-of-function experiments showed that the appearance and internal structure of ZZ embryonic gonads with sox9 knockdown underwent significant feminization, and the germ cells presented female distribution pattern. The mRNA expression of male specific gene dmrt1 and amh significantly decreased, and that of female specific gene foxl2 obviously increased. Besides, the expressive signals of the DMRT1 protein almost disappeared, while FOXL2 protein was activated and abundantly expressed, indicating complete sex reversal from male to female on gonads(ratio of reversal: 87.9%). The results of the gain-of-function experiments showed that 42.5% of ZW embryos overexpressing sox9 differentiated towards male. The expression of dmrt1 and amh were upregulated while foxl2 was downregulated, and the fluorescent signals of both DMRT1 and FOXL2 were detected simultaneously in the same gonad, indicating incomplete sex reversal. These findings above demonstrate that sox9 is the necessary gene for early testicular formation in P. sinensis, and it does participate in the process of regulating male differentiation, which establishes theoretical foundation for the following analysis of sexual differentiation mechanism of P. sinensis and provides breeding target for realizing the sex control of P. sinensis at the same time.

• Effects of high-temperature stress on the histopathology of gills and liver tissues and serum biochemical indicators of Hucho taimen

  ZHANG Tan, TONG Guangxiang, XU Huan, YAN Ting, WEI Mingliang, ZHANG Tingting, KUANG Youyi

  2025,49(6):069106-069106, DOI: 10.11964/jfc.20240214383

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  Temperature fluctuations caused by climate change and global warming pose significant threats to various species. Understanding the mechanisms of fish tolerance to high temperatures can help develop effective strategies to cope with climate changes in aquaculture. Hucho taimen is an important economic cold-water salmonid. This study designed a temperature acclimation protocol that included gradual warming from an optimal 18 ℃ to 26 ℃, maintaining 26 ℃ for 7 days, and then reducing the temperature back to 18 ℃. The impact of high temperature on taimen was compared and analyzed through respiratory rate, histopathology, and serum biochemical indicators. The results demonstrated that during the gradual temperature increase from the optimal 18 ℃ to 26 ℃, the respiratory rate of taimen accelerated with rising temperature. Histopathological changes in gills and liver tissues at the cellular level progressively worsened, including hypertrophy and rupture of gill epithelial cells, as well as hepatocellular hypertrophy, vacuolization, and necrosis. At 26 ℃, the pathological grad reached a severe level (with lesions comprising over 61% of the tissue). Serum enzyme activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activities sharply increased with the rising temperature. Alkaline phosphatase (ALP) activity remained unchanged at 22 ℃ but significantly decreased at 26 ℃. The total cholesterol (TC) content gradually decreased, while the total protein (TP) content initially decreased and then recovered. During the 7-day period of high temperature at 26 ℃, the respiratory rate of taimen remained consistently higher than that of control group. Histopathological deterioration of in the gills and liver tissues further intensified, including epithelial necrosis, vascular occlusion, and secondary lamellar fusion in the gills, as well as hepatic congestion, lipid infiltration, and inflammatory cell infiltration. The histopathological grad peaked at 105 h, followed by a gradual decrease in lesions. Serum enzyme activities of AST, ALT, and LDH activities initially decreased sharply and then increased, while ALP activity at first increased and then normalized. TC content slowly recovered, and TP content initially decreased and then returned to normal. After returning to 18 ℃ from 26 ℃, the respiratory rate returned to normal levels, gill tissues recovered completely, and liver tissues had partial recovery, though there was moderate lipid infiltration and inflammatory cell infiltration (lesions comprising 31%-60% of the tissue). Serum enzyme activities of AST, ALT, and LDH activities decreased but remained significantly higher than that of the control group, while ALP activity showed a sharp increase. TC and TP contents restored to normal levels. The study found that the respiratory rate of taimen increased with rising temperatures, and high-temperature stress caused the respiratory rate to remain elevated above normal levels. This demonstrated an increased oxygen demand and metabolic rate under high-temperature stress. High-temperature stress induced various types and degrees of lesions in the gill and liver tissues of taimen. After the temperature returned to normal, the gill tissues recovered, while the liver tissues showed partial recovery but remained in a significantly pathological state. High-temperature stress affected the liver functions related to metabolism, synthesis, and storage, with a more significant impact on metabolic capacity. The combined analysis of respiratory rate, pathology, and biochemical indicators suggests that taimen has some adaptive capacity to high-temperature stress. These findings of this research provide a theoretical foundation for the physiological regulatory mechanisms of temperature tolerance in taimen, as well as for the efficient aquaculture and selection of high-temperature resistant strains.

• Effects of high temperature on the physiological metabolism and antioxidant levels of Sinonovacula constricta

  LI Chun, LIU Qi, CHEN Yukuan, YUAN Li, NIU Donghong

  2025,49(6):069107-069107, DOI: 10.11964/jfc.20230514032

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  Due to factors such as drought, tides, rainfall and human activities, the temperature of seawater in the nearshore intertidal zone fluctuates greatly, and the organisms such as shellfish living there are susceptible. Therefore, in order to explore the effect of high temperature stress on shellfish, the razor clam (Sinonovacula constricta) was used as the model organism in this study. The control group (24 °C) and the high temperature groups (28 °C, 32 °C) with a stress time of 72 hours were set up to start the comparative experiments. The survival rate, oxygen consumption rate and ammonia excretion rate of the S. constricta were sampled at 0, 6, 12, 24, 48 and 72 h, respectively. The activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA) in the hepatopancreas and gill of them were determined at the same time. The results showed that the survival rate of S. constricta at 28 and 32 °C were 27.80%±4.15% and 20.00%±2.69%, respectively, which were significantly lower than that at 24 °C 85.60%±1.60%. With the increase of temperature, the oxygen consumption rate and ammonia excretion rate of S. constricta also increased, and reached the maximum value at 32 °C. SOD activity and MDA content in the hepatopancreas and gill tissues increased with the increase of temperature, and showed a trend of first increasing and then decreasing with the extension of time. The results demonstrated that under acute high temperature stress, the physiological metabolic activities of S. constricta intensified, but still maintained a certain survival rate and antioxidant capacity. The study can provide a data reference for the cultivation of new strains of S. constricta with high temperature resistance.

• Effects of hypoxic stress on energy metabolism, oxidative stress and immune function in Onchidium reevesii

  ZHANG Xiaoming, TU Zhihan, XIAO Haiming, RAO Rongcheng, CHEN Xilin, QIAN Chang, SHEN Heding

  2025,49(6):069108-069108, DOI: 10.11964/jfc.20211113140

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  This study explored the effects of hypoxic stress on energy metabolism, oxidative stress and immune function of Onchidium reevesii. In this experiment, under hypoxic conditions [DO = (2.0 ± 0.2) mg/L], the changes of serum and hepatopancreatic biochemical indexes and the expression of hepatopancreas-related genes at 0, 4, 8, 12, and 24 h were measured. The results showed that among the energy metabolism indexes, serum blood glucose, liver glycogen, serum and hepatopancreas lactic acid levels all increased significantly with the passage of hypoxic stress. Among the antioxidant indicators, catalase (CAT) activity and reduced glutathione (GSH) content showed an upward trend and then a downward trend. All reached the maximum at 8 h, which were significantly higher than the control group. The content of malondialdehyde (MDA) showed an upward trend with the passage of hypoxic stress and was significantly higher than that of the control group. Among the immune indicators, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) showed a fluctuating upward trend, and both were significantly higher than the control group. And serum ALT and AST were higher than hepatopancreas from 8 h. The expression of glycogen phosphorylase (GP) mRNA in hepatopancreas increased significantly under hypoxic stress. The expression of glutathione peroxidase (GSH-Px) mRNA and heat shock protein 70 (Hsp70) mRNA showed an upward trend and then a downward trend, and all reached the maximum at 8 h, which was significantly different from the control group. Research showed that O. reevesii mainly carries out anaerobic metabolism in order to adapt to the hypoxic environment, and hypoxic stress affects the antioxidant capacity and immune function of the body.

• Spatial patterns of fish diversity in the Chongqing section of the Yangtze River Basin based on eDNA

  ZHANG Yufeng, ZHOU Xinxin, LI Qinghua, ZHANG Jiaming, SHEN Yanjun

  2025,49(6):069309-069309, DOI: 10.11964/jfc.20230814109

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  Fish diversity not only plays a pivotal role in maintaining the balance and stability of aquatic ecosystems, but also serves as a critical indicator for assessing the health status of freshwater ecosystems. However, prolonged anthropogenic disturbances, including hydraulic development, environmental pollution, and the introduction of exotic fish species, have resulted in varying degrees of habitat degradation for ichthyofauna in the Chongqing section of the Yangtze River Basin, posing severe threats to contemporary fish biodiversity. This study aimed to investigate the current status and spatial pattern evolution of fish diversity in the Chongqing section of the Yangtze River Basin following reservoir impoundment. From May to June 2022, environmental DNA (eDNA) technology was employed to survey fish diversity across six mainstream sections (from Jiangjin to Wushan) and eight important primary tributary sections. A total of 107 fish species were detected, belonging to 7 orders, 20 families, and 74 genera. These included 6 nationally protected species, 17 endemic species to the upper Yangtze River, and 12 exotic species. Comparative analysis of post-impoundment periods revealed an increase in exotic species compared to the trial operation phase of the Three Gorges Reservoir. Notably, the proportion of rheophilic fish species declined, while eurytopic fish species increased. Tributary habitats exhibited higher alpha diversity indices than adjacent mainstream sections. The grouping model demonstrated that the Jiangjin-Fuling section had a higher average alpha diversity index than the Fuling-Wushan section, with statistically significant differences in fish community composition between the groups. This study elucidates the current status and spatial pattern evolution of fish diversity in the Chongqing section of the Yangtze River Basin. It further validates the feasibility and efficiency of eDNA technology for fish diversity monitoring, positioning it as a robust complement to traditional survey methods.

• Risk assessment of invasive fish species in the middle and upper reaches of the Yangtze River (including Dongting Lake)

  TIAN Panpan, DENG Huatang, WANG Daoqun, YU Lixiong, GAO Lei, LIU Shaopin, CHEN Daqing, DUAN Xinbin, WANG Ke, TIAN Huiwu

  2025,49(6):069310-069310, DOI: 10.11964/jfc.20231214263

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  To understand the current status of exotic fishes in the middle and upper reaches of the Yangtze River and to assess their invasion risks, investigations on exotic fishes were conducted using fixed gill nets, drift nets, and ground traps at 22 river sections of the main stream and tributaries of the middle and upper reaches of the Yangtze River, as well as at Dongting Lake and Honghu Lake from May to July and from October to December in 2022. The results showed that a total of 135 species of fish belonging to 8 orders 24 families 20 species of exotic fishes were collected during the survey period. The investigation in the Jiangjin section revealed the highest number of exotic fish species, with the highest occurrence frequency being the exotic sturgeon. Through the Fish Invasion Screening Test (FIST), six high risk invasive fish species were preliminarily screened, including Oreochromis niloticus, Coptodon zillii and Cyprinus carpio. Further analysis of invasion risk was conducted using the Fish Invasion Screening Kit (FISK), and a total of 8 species of fish were identified as high invasion risk, C. zillii, Clarias lazera and Cirrhina mrigalancluding. The ROC curve was used to validate the FISK scoring results, which showed an AUC value of 0.944, indicating that the FISK evaluation method has a high ability to distinguish species invasiveness and can distinguish whether foreign fish have invasion risks in the study water under current and climate change scenarios. Research has shown that based on the risk assessment results of invasive fish species mentioned above, there are already multiple high-risk fish species in the middle and upper reaches of the Yangtze River, which may seriously endanger the fishery resources and the structure and function of the aquatic ecosystem in the middle and upper reaches of the Yangtze River. It is recommended to increase the management and control of high-risk invasive species, while strengthening the protection of indigenous fish populations, in order to avoid significant damage to the Yangtze River indigenous fish resources caused by invasive species. This study can provide countermeasures for the protection of Yangtze River indigenous fish resources.

• Comparative analysis of osmoregulatory capacity in freshwater-cultured juveniles of Acipenser sinensis and A. dabryanus

  WANG Puyuan, LENG Xiaoqian, REN Feixiang, ZHONG Jia, CHENG Peilin, ZHANG Lining, QIAO Xinmei, DU Hao

  2025,49(6):069111-069111, DOI: 10.11964/jfc.20231214265

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  Acipenser sinensis and Acipenser dabryanus are flagship species in the Yangtze River Basin. Due to the severe decline of natural resources, establishing artificial conservation populations and breeding and releasing them have become key measures for repairing wild populations. A. sinensis and A. dabryanus belong to the sisters species in the evolutionary relationship. As an important feature of species differentiation, the difference in natural life history suggests that there may be a huge difference in the osmotic pressure regulation mechanism of salinity adaptation between the two at the juvenile stage. The migratory habits of sturgeons give them unique living habits in rivers and oceans. Studying the osmotic regulation of sturgeons is of great significance for understanding their physiological characteristics and protecting this rare species.In order to investigate the difference of osmotic adjustment ability of juvenile A. sinensis and A. dabryanus in adapting to seawater. Freshwater cultured juvenile A. sinensis and A. dabryanus as research subjects, and the seawater domestication experiment was carried out by continuous salt elevation. The osmotic pressure, Na⁺ content, cortisol, gill Na⁺/K⁺-ATPase (NKA) activity and gill tissue structure changes of juvenile A. sinensis and A. dabryanus were compared and analyzed at 0, 9, 19, 28 during acculturation. The results of serum indexes showed that the serum osmotic pressure of juvenile A. sinensis and A. dabryanus increased with the increase of environmental salinity, but the serum osmotic pressure of A. sinensis was significantly lower than that of A. dabryanus at high salinity. Similarly, the serum Na⁺ content of A. sinensis was significantly lower than that of A. dabryanus. The serum cortisol content of juvenile A. sinensis increased significantly, while that of A. dabryanus had no significant change. Gill NKA test results showed that the gill NKA activity of A. sinensis increased significantly at high salinity, and that of A. dabryanus increased at 9 ppt, but decreased significantly at high salinity. H&E staining of gill tissue showed that the diameter and number of secreting chlorine cells of juvenile Chinese and A. dabryanus increased significantly with the increase of salinity. However, under the condition of hyperosmosis, the gill filaments of juvenile Yangtze River sturgeon showed complete loss of structure, and the flat epithelial cells of gill lamella showed different degrees of shedding or separation. The results showed that juvenile A. sinensis had strong osmotic regulation and adaptability in a high salinity environment. The body could enhance gill filament NKA activity through the regulation of hormone levels, stimulate the increase in the diameter and number of gill epithelial chlorine cells, and achieve ion exhalation and osmotic pressure balance in a high salinity environment. However, the salinity adaptation range of juvenile A. dabryanus is poor and when the salinity exceeds a certain tolerance range, it will cause irreversible effects on the organizational structure. The findings provided basic data for the exploration of land-sea relay protection model of A. sinensis.

• Reproductive biology of Synechogobius hasta

  XU Xinghong, QI Lu, WU Tong, LIU Shun, LI Tiezheng, ZHAO Ziyan, ZHU Long, LIN Chunmei, XU Guocheng

  2025,49(6):069112-069112, DOI: 10.11964/jfc.20230914171

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  Javelin goby (Synechogobius hasta) is an important part of the coastal fishing of China, Japan and Korea, which has high economic and development value due to its tender meat and delicious taste with abundant protein and polyunsaturated fatty acid. In order to understand the breeding characteristics, the adult S. hasta collected from Haizhou Bay were used as materials to detect the data about sex ratio, fecundity and germ cells for analyzing the gonad feature and law of embryonic development, besides, the effect of main environmental factors on the fertility rate of S. hasta were also assessed by orthogonal experiments in this study. The results showed that sex ratio of S. hasta between the female and male was 1.03∶1.00 in the non-reproductive period and 3.26∶1.00 (P<0.05) in the reproductive period, respectively, which indicated the number of females was significantly more than males in the breeding stage. The individual differences in fecundity of S. hasta were large, with a maximum value of 7.15 times the minimum. The absolute fecundity ranging from 5 987 to 42 828 (19 655±12 551), while the relative fecundity ranging from 42 to 263 (144±59), and significant positive correlation between brood amount and body weight were recorded (R=0.82). In early March, the male fish delivered the spermatophore to the female abdominal cavity before the matures of female fish. A small amount of spawning was observed in mid- March, and a large number of concentrated spawning occurred in early April. The type of goby’s ovium was anisolecithal, and the mature ovium were at the stage of the middle of the second mature division. The mature ovium was light yellow, translucent and agglutinant containing several oil balls with the diameter of (1.53±0.16) × (1.33±0.20) mm. The sperm density was (1.43±0.14)×10⁹ ind/mL, and the average number of sperm produced by each male was (5.43±0.53)×10⁹ ind. Embryonic development process included 7 stages: placental formation, cleavage, blastula, gastrula, neurula, organ formation and hatching, in which the organ formation stage also consisted of body segment stage, optic rudiment stage, capsula opitca stage, tail bud stage, eye crystal stage, muscular contraction effect stage, otolith stage, heartbeat stage and eye pigment deposition period. Under the conditions of incubation water temperature (17±1) ℃, it took 149 h 50 min to hatch, and the required accumulated temperature was 2 455.82 h·℃. The results of orthogonal experiments showed that the highest fertility rate was obtained under the conditions of temperature of 19℃, the salinity of 32, and pH 8.0. The influence of environmental factors was in the following order: salinity>pH>temperature. In conclusion, the female gonad of S. hasta matured later than that of the male fish; the embryo development period was relatively long, and the fertilization rate could be improved by higher water salinity. This study preliminarily clarified the timing characteristics of the embryonic development of S. hasta, enriched the basic data of reproductive biology, and provided theoretical evidence for the artificial breeding and conservation of germplasm resources.

• Comparison of three tetraploid induction pathways in the Pacific oyster (Crassostrea gigas) "Haida No.2"

  CHENG Geng, ZHANG Haining, LIANG Yuanxin, XU Chengxun, LI Qi

  2025,49(6):069613-069613, DOI: 10.11964/jfc.20240114323

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  Tetraploid of Crassostrea gigas "Haida No.2" was induced by cytochalasin B (CB) and hypotonic treatment under pathway Ⅰ (2n♀+2n♂), pathway Ⅱ (3n♀+2n♂) and pathway Ⅲ (2n♀+4n♂), and this study compared the three pathways in the aspects of cleavage rate, D larvae rate, tetraploid rate of larvae and spat. The effects of three factors including reagent treatment intensity, induced occasion and induced duration were also discussed. The results showed that under pathway Ⅰ (2n♀+2n♂), the highest tetraploid rate of 28.37% was obtained in larval stage treated with 0.5 mg/L CB, and 20 min for duration time of induction when the first polar body of fertilized eggs appeared. Under this pathway, tetraploid larvae could not be detected using hypotonic treatment. Under pathway Ⅱ (3n♀+2n♂), the highest larval tetraploid rate of 52.64% was obtained in larval stage treated with 0.5 mg/L CB, and 20 min for duration time of induction when the first polar body of fertilized eggs appeared. Under this pathway. Under this pathway, when the first polar body of fertilized eggs appeared, the highest larval tetraploid rate of 26.64% was obtained after 20 min of treatment using seawater with a salinity of 8. Under pathway Ⅲ (2n♀+4n♂), the highest larval tetraploid rate of 60.45% was obtained in larval stage after 20 min of duration time with 0.75 mg/L CB when 30% PB1 appeared. Under this pathway, the highest larval tetraploid rate of 25.51% was obtained after 20 min of treatment using seawater with a salinity of 8 when 30% PB1 appeared. Under the optimal induction conditions, the ploidy of the spats (60 days) was analyzed by flow cytometry to determine their composite ploidy under optimal induction conditions. The tetraploid rate of the spats in the CB-treated group under pathway Ⅰ (2n♀+2n♂) was 4%, which was a decrease of 24.37% compared with that of the larval stage (28.37%); no tetraploid juvenile shells were detected in the hypotonic treatment group. The tetraploid rate of the spats in the CB-treated group and the hypotonic treatment group reached 80% and 30% under pathway Ⅱ (3n♀+2n♂), which decreased by 27.36% and 3.36%, respectively, compared to the larval stage (52.64% and 26.64%, respectively).The tetraploid rate of the spats of CB-treated and hypotonic treatment groups under pathway Ⅲ (2n♀+4n♂) reached 10% and 4%, which was a decrease of 50.45% and 21.51%, respectively, compared with that of the larval stage (60.45% and 25.51%, respectively). Comparing the three pathways and two induction methods, the best choice for the production of tetraploid of C. gigas "Haida No.2" is to use CB to induce tetraploid through pathway Ⅱ (3n♀+2n♂).

• Chromosome preparation and karyotype analysis of gynogenetic diploids and haploids in Ruditapes philippinarum

  LI Qiang, NIE Hongtao, WANG Bin, ZHOU He, HUO Zhongming, YAN Xiwu

  2025,49(6):069614-069614, DOI: 10.11964/jfc.20240314405

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  Abstract:

  Gynogenesis is an important breeding method for rapid establishment of pure lines. Karyotype analysis of gynogenetic offspring of Ruditapes philippinarum has not been reported. In order to clarify the karyotype of gynogenetic diploid, haploid and normal diploid of R. philippinarum. In this experiment, the gynogenetic diploid, haploid and normal diploid larvae of R. philippinarum were selected. The chromosome drops were made by air-drying technique, and the number of chromosomes was counted and karyotype analysis was carried out. The results showed that the number of chromosomes in gynogenetic diploid and normal diploid of R. philippinarum was 38, and the haploid was 19. The results of karyotype analysis showed that the karyotype formula of gynogenetic diploid and normal diploid of R. philippinarum was 2n=18m +20sm, NF=76, and the haploid karyotype was n=9m+10sm, NF=38. No sex chromosome and satellite were found in chromosome morphology. Studies have shown that clams have only two types of chromosomes, m and sm. The karyotype of gynogenetic diploid is the same as that of normal diploid, and the type of haploid chromosome is the same as that of normal diploid and the number is half of that of diploid. In this study, the metaphase division phase and karyotype analysis results of gynogenetic diploid, haploid and normal diploid of R. philippinarum were obtained by air-drying technique using the trochophore larvae of R. philippinarum as materials, which enriched the related research of gynogenetic and haploid chromosomes of R. philippinarum and the cognition of chromosome number and karyotype composition of R. philippinarum. At the same time, it has important reference value for the study of cytogenetics and genetic breeding of R. philippinarum.

• Adaptive responses of Hyriopsis cumingii to different purple soils under high-temperature stress

  MEI Jing, YANG Qinglin, TANG Xiaoqi, LIU Yang, LI Yanhong, YU Xiaobo, WU Zhengli

  2025,49(6):069615-069615, DOI: 10.11964/jfc.20230714091

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  Abstract:

  Soil sediment constitutes a vital element within pond aquaculture systems, exerting a profound influence on the growth and disease resistance of cultivated animals. In recent years, aquaculture has been under severe threats due to extreme thermal weather conditions. To scrutinize the impact of different sediment types on the high-temperature stress resistance of Hyriopsis cumingii, this study constructed a 28-day aquaculture experiment employing three different purple soils (S1, Feixianguan group; S2, Shaximiao group; S3, Suining group) as sediment. Regular assessments of water quality indicators [ammonia nitrogen (NH₄⁺-N), nitrite nitrogen (NO₂^--N), nitrate nitrogen (NO₃^--N), total nitrogen (TN), total phosphorus (TP), active phosphorus (AP), chemical oxygen demand (COD), total hardness (TH)] across varied aquaculture systems were conducted. After the completion of the aquaculture phase, H. cumingii in diverse systems were subjected to ambient (23 °C) and high-temperature (33 °C) conditions. Hemolymph antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT)], immune-related enzymes [alkaline phosphatase (AKP), lysozyme (LZM)] activities and H₂O₂ levels were measured at 6 h and 12 h after exposure, and the expression of hepatopancreas immune related genes (IAP, IL-17, HSP70) was analyzed. The results revealed differences in water quality indicators among the three aquaculture systems during the cultivation of H. cumingii. The system using S3 purple soil as sediment had the highest TP levels (peak value: 1.13 mg/L) and lower NO₂-N concentrations (peak value: 0.12 mg/L) compared to the other systems, resulting in a more favorable environment for the growth and health of the cultured organisms. Following high-temperature stress, the activities of SOD and CAT in H. cumingii cultured in S3 purple soil increased to 1.2- to 2.0-fold of those in the control group, and the expression of IAP, IL-17, and HSP70 genes was significantly up-regulated (1.2- to 13.0-fold), indicating enhanced thermotolerance. The adaptability hierarchy among distinct bottom sediment aquaculture systems, in terms of resisting high-temperature stress in H. cumingii, was ranked as S3 > S1 > S2. These findings contribute to a more profound comprehension of the influence of aquaculture sediment on the high-temperature resistance of aquatic organisms.

• The early developmental process of Acanthaster solaris in the South China Sea

  ZHOU Zihua, Lü Yihua, ZHENG Chengzhi, JIA Houlei, LU Chuqian, GENG Zhiqiang, XIONG Xiaofei, LOU Quansheng

  2025,49(6):069616-069616, DOI: 10.11964/jfc.20230914145

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  Abstract:

  Crown-of-thorns sea star (CoTS), a well-known coral predator, has triggered severe ecological disaster on coral reefs in the South China Sea. In order to clarify the early development process of this coral predator and better explain the formation process of CoTS outbreak, an artificial breeding was conducted for the outbreak population of Acanthaster solaris in the South China Sea with the method of reproductive biology. The result demonstrated 1-methyl-adenine was effectively induced to foster A. solaris to spawn. When under the temperature of 28 ℃ and salinity of 33 as the natural seawater of coral reefs, a batch of embryos completed incubation process and developed into bipinnaria larva. With feeding on Chaetoceros muelleri, two newly-formed arm protruded from the anteroventral part of the planktonic larva after 12 d post-fertilization, a feature designated as early branchiolaria larva. Upon two days metamorphosis, larva was successfully developed into 5-arms settled juvenile with totally 410 juveniles and the average size of (445.88 ± 50.63) μm (mean ± SD). It was found that in the comparison between artificial food and natural food, artificial food could not promote the conversion of planktic larvae into branchiolaria larvae and natural food was still needed for the planktic development. Notably, in the experiment of present or absent attached bases, coral stone can effectively promote the metamorphosis development of settled juveniles with the mean metamorphosis rate 2.59%, higher than that of no attached bases with the value only 0.31%. In this study, a number of progenies of A. solaris population were successfully bred in artificial breeding, revealing their early developmental process. The result here provided basic data for investigation, monitoring, early warning, disaster reduction, prevention and control, and disaster management of A. solaris, which finally fostered the ecological security of islands and reefs in the South China Sea.

• Effects of duckweed (Lemna minor) biomass on epiphytic diatom colonization under aeration disturbance

  PAN Hengfeng, WANG Xiaodong, CHE Xuan, WANG Hong, LI Yiming, CHENG Xiangyu, LIU Xingguo

  2025,49(6):069617-069617, DOI: 10.11964/jfc.20230814106

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  Abstract:

  Diatoms (Bacillariophyta) have important biological significance and application value. Diatoms are important primary producers in water bodies and can serve as bait for many fish, shellfish, and other aquatic animals, thus playing a crucial role in aquatic ecosystems, particularly in aquaculture. The high-density cultivation of diatoms, particularly epiphytic species, represents a critical research frontier in aquaculture. However, there is currently limited research on using natural aquatic plants to cultivate epiphytic diatoms. In order to cultivate epiphytic diatoms with Lemna minor, a culture experiment was conducted with decaying L. minor in different biomass under aeration disturbance. According to the wet biomass gradient of the rotting L. minor, a total of 5 treatments were set as 0, 4, 8, 12 and 14 g/L, named as treatment Ⅰ, Ⅱ, Ⅲ, Ⅳ and Ⅴ from low to high, respectively, each with 3 replicates. The results showed that no hypoxia occurred in any of the treatments. The concentrations of ammonia nitrogen (NH₄⁺-N) and soluble reactive phosphorus (SRP) in treatment Ⅰ [(0.584±0.649) and (0.336±0.274) mg/L, respectively] were significantly higher than those in the other treatments (P<0.05). The dissolved total nitrogen (DTN) and dissolved total phosphorus (DTP) concentrations in all treatments exhibited a declining trend before stabilizing, with no significant differences observed between treatments. Although treatment V had the highest mean DTN [(1.665±1.678) mg/L] and DTP [(0.603±0.672) mg/L] concentrations, these values were not statistically significant. In the middle and late stages of the experiment, diatoms of Navicula and Cocconeis appeared on the rotting L. minor, and the wet weight of the epiphytic diatoms of treatment Ⅳ was the highest (P<0.05), reaching the maximum of 249.13 mg/L on the 35th day. The maximum biomass of epiphytic diatoms on L. minor was significantly higher than that on glass sheetS (P<0.05). The results show that the wet biomass of rotting L. minor at 12 g/L is more conducive to the growth of epiphytic diatoms under aeration disturbance, and L. minor are more beneficial to the growth of epiphytic diatoms than glass sheet. The rotting L. minor releases nutrients such as nitrogen and phosphorus, providing a material basis for the growth of diatoms and serving as a medium for the diatoms’ attachment growth. This experiment provides a feasible method for cultivating epiphytic diatoms in a decaying state of L. minor under aeration disturbance, expanding the cultivation method of epiphytic diatoms.

• Acartia huangi sp. nov., a new species of Acartia from the Taiwan Strait

  GONG Zhidi, GUO Donghui

  2025,49(6):069118-069118, DOI: 10.11964/jfc.20231214294

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  Abstract:

  Acartiids are diminutive copepods geographically distributed across temperate and tropical zones, dominating zooplankton biomass in.estuarine and near coastal waters. They not only play an important role in the zooplanktonic community, but also hold significant importance in aquaculture. With high nutritional value and adult sizes generally not exceeding 2 mm in length, Acartiids serve as excellent live prey for fish, shrimp, and crab larvae during the artificial propagation of aquatic animals. The present study describes a new species of Acartia Dana, 1846, A. huangi Guo & Gong, sp. nov., which was collected from the Taiwan Strait between 2004 and 2020. In order to accurately identify the new species, this study was conducted based on integrated morphological and molecular analyses. Morphologically, this new species should be assigned to subgenus Odontacartia Steuer, 1915, characterized by the existence of rostral filaments, posterior corners of last pedigerous somite drawn out into lateral spines, and the male's 2nd urosome has a posterodorsal margin with pointed processes. A. huangi Guo & Gong, sp. nov. mostly resembles A. erythraea s. l., but differs in the following characteristics: ① 2^nd segment of female antennule with 2 spines posteriorly, while that of A. erythraea s. l. with 4 spines; ② 3^rd segment of female fifth thoracic leg (P5) with 2 columns of spinules on the inner side, while both sides of female P5 smooth in A. erythraea s. l.; ③ each inner side of posterior corners of last pedigerous somite with 2 spines dorsally in male, while that of A. erythraea s. l. with only 1 spine dorsally; ④ posterodorsal margin of 3^rd urosomite with 4 to 9 spines in male, while that of A. erythraea s. l. with only 2 spines; ⑤ the inner margin of 4^th segment of male left P5 with a bifurcate process, while that of A. erythraea s. l. with a finger-like process. The mitochondrial cytochrome oxidase Ⅰ (mtCOⅠ) gene sequences supported the results based on morphological data with showing pairwise genetic distances of 0.182-0.194 with this species and A. erythraea s. l.. The phylogenetic tree using unweighted pair group method with arithmetic means (UPGMA) based on mtCOⅠgene sequences also clearly distinguished individuals of two species, and clearly distinguished the new species from A. erythraea s. l.. This new species was named in honor of Prof. Huang Jiaqi (1941–2022) of Xiamen University for his excellent contributions to marine planktology. Type specimens of A. huangi Guo & Gong, sp. nov. were deposited in Museum of Marine Science and Technology, Xiamen University. This study not only enriches the species diversity of Acartia in China, but provides basic data for database of diet organisms and marine biological survey.