Heat stress (HS) triggers reactive oxygen species (ROS) accumulation and activates stress-responsive signaling pathways, including c-Jun N-terminal kinase (JNK) and nuclear factor kappa B (NF-κB) in fish hepatocytes. However, how ROS, JNK, and NF-κB interact under HS and recovery remains poorly understood. In this study, we investigated these interactions in largemouth bass primary hepatocytes. First, we examined intracellular ROS levels and activation of JNK and NF-κB in hepatocytes immediately after HS (37 °C, 2 h) and during recovery (2, 6, 12, and 24 h). ROS levels and phosphorylated JNK significantly increased after HS and remained elevated throughout recovery, while NF-κB activation was observed at 6, 12, and 24 h after HS. Next, their regulatory relationship was investigated by pretreating hepatocytes with specific inhibitors prior to HS and allowing a 24-h recovery. JNK inhibitor SP600125 had no effect on ROS accumulation, whereas the ROS inhibitor N-acetylcysteine significantly reduced JNK activation, suggesting that ROS is functionally associated with JNK activation in this context. Furthermore, inhibition of either JNK or ROS significantly suppressed NF-κB activation, whereas the NF-κB inhibitor BAY11-7082 led to increased ROS accumulation and JNK activation, indicating a possible compensatory mechanism. Finally, we assessed whether these three signaling molecules regulate HS-induced apoptosis in hepatocytes. Inhibiting ROS or JNK reduced apoptosis, increased mitochondrial membrane potential, and decreased Caspase-3 activity. In contrast, NF-κB inhibition enhanced apoptosis. Collectively, our findings indicate that NF-κB may plays a protective role during HS recovery in fish by attenuating apoptosis through modulation of ROS/JNK signaling.

Largemouth bass (Micropterus salmoides), an important species in both aquatic ecosystems and aquaculture, is increasingly affected by heat extremes. Heat stress poses significant challenges to fish health, particularly affecting key organs like the gills. This study investigated the effects of heat stress (37 °C) on the gills of juvenile largemouth bass, focusing on histopathology and molecular adaptations, including genome-wide gene expression and DNA methylation. After the heat stress experiment, histological analysis of hematoxylin and eosin-stained gill tissues revealed significant alterations, including increased blood cell density, epithelial cell proliferation, and curling of gill lamellae. Ultrastructural analysis via transmission electron microscopy showed irregular cell shapes of the secondary lamellae. TUNEL staining demonstrated a significant increase in apoptotic cells, from 14.53 % in control fish versus 69.58 % in heat-stressed fish, which correlated with upregulation of apoptosis-related genes, such as caspase3 and p53. Transcriptomic analysis using RNA sequencing identified 608 differentially expressed genes. KEGG enrichment analysis revealed significant enrichment of the "protein processing in endoplasmic reticulum" pathway. Additionally, whole-genome bisulfite sequencing and methylomic analysis identified 12,505 differentially methylated regions. GO enrichment analysis of genes containing promoter DMRs identified 44 significantly enriched terms, including "metabolic process," "organic substance metabolic process," "binding" and "protein interaction." Notably, genes associated with apoptosis, such as capn3a, dok4, rassf7a, and tusc2a, exhibited significant changes in both gene expression and DNA methylation in their promoters. These findings provide insights into the molecular responses of fish gills to heat stress and mechanisms of resilience in cultured fish species under changing environmental conditions.

Understanding the impacts of environmental conditions at early life stages on phenotypes and physiological responses to thermal variability at later stages is crucial for elucidating adaptive strategies in fish species. This study investigated the lasting effects of embryonic temperature on the growth performance, transcriptomic profiles, and CpG methylation status of juvenile largemouth bass (Micropterus salmoides) under normal and heat stress (HS) conditions. Embryos were incubated at three temperatures (22 °C, 25 °C, and 28 °C), reared at a constant 25 °C for three months, and subjected to acute HS at 37 °C. Liver samples were collected before and after HS for mRNA sequencing and reduced representation bisulfite sequencing. Significant differences in body size, body weight, condition factor, and hepatosomatic index were observed among groups. Fish hatched at 28 °C displayed a significantly higher standard length and body weight and lower hepatosomatic index than those hatched at lower temperatures. PCA analysis and Venn diagrams based on transcriptomes revealed transcriptomic response to HS differed at 28 °C while 22 and 25 °C were similar. Heat shock protein genes followed a similar trend. Epigenetic analyses revealed distinct CpG methylation patterns across incubation groups, while DNA methylation barely contributes to transcriptional differences. Under HS, different incubation groups exhibit various DNA methylation alterations. The “Neuroactive ligand-receptor interaction” pathway appeared to play an important role in the response to HS, suggesting a potential involvement of epigenetic regulation. Additionally, the atrnl1 gene may be involved in a DNA methylation-mediated regulatory mechanism in response to HS.

Global warming threatens freshwater ecosystems and compromises fish survival. To elucidate the role of miRNAs in the livers of heat stressed largemouth bass, juvenile fish was subject to heat stress under 37 °C. Both mRNA-seq and miRNA-seq were conducted on the liver tissues under control and heat stress conditions. Differential gene expression analysis and enrichment analysis were performed on mRNA and miRNA expression profiles. A total of 406 differentially expressed genes (DEGs) were discovered, of which 212 were up-regulated and 194 were down-regulated. Most of the DEGs were significantly implicated in the regulation of “protein processing in endoplasmic reticulum”, “proteasome”, “steroid biosynthesis”, and “ornithine decarboxylase inhibitor activity” pathways. In addition, 47 differentially expressed miRNAs (DEMs) were identified in largemouth bass livers under heat stress, including 21 up-regulated and 25 down-regulated miRNAs. A negatively regulated miRNA-mRNA network including 12 miRNAs and 19 mRNAs was constructed with DEMs involved in “protein degradation”, “calcium ion regulation”, “cell apoptosis”, and “lipid metabolism”. Moreover, this study indicated novel-miR-144 activated the IRE1 signaling pathway by targeting txndc5 to induce liver apoptosis in largemouth bass under heat stress. This study revealed the involvement of miRNA regulation in largemouth bass in response to heat stress.

The increasing frequency of high-temperature extremes threatens largemouth bass Micropterus salmoides, a significant fish for freshwater ecosystems and aquaculture. Our previous studies at the transcript level suggested that heat stress induces hepatic apoptosis in largemouth bass. In the current study, we sought to validate these findings and further investigate the role of the c-Jun N-terminal kinase (JNK)/P53 signaling in hepatic apoptosis under heat stress. First, heat treatments were conducted in vivo and in vitro under different temperatures: 28 °C, 32 °C, and 37 °C. In primary hepatocytes subjected to heat treatment, cell viability was evaluated via the Cell Counting Kit-8, while mitochondrial membrane potential and nuclear morphology were assessed through JC-1 and Hoechst 33258 staining, respectively. We observed reductions in both cell viability and mitochondrial membrane potential (ΔΨm), along with alterations in nuclear morphology, in primary hepatocytes exposed to heat stress at temperatures of 32 °C and 37 °C. Quantitative real-time PCR revealed significant alterations in the expression profiles of intrinsic apoptosis-related genes within liver tissues under heat stress. Immunohistochemistry analysis revealed that JNK1 signaling increased as the temperature increased, JNK2 expression increased only at 37 °C, and JNK3 expression did not change with temperature. We speculate that JNK1 and JNK2 have pro- and anti-apoptotic effects, respectively. Western blot analysis conducted on cultured hepatocytes further validated these findings. JNK inhibition reduced hepatocyte apoptosis, improved nuclear morphology, and maintained ΔΨm even after 37 °C treatment. These results not only confirm that heat stress led to intrinsic apoptosis of hepatocytes but also indicated that JNK1 could mediate P53 expression and activate caspase-dependent intrinsic apoptosis in largemouth bass hepatocytes under such conditions. This study illuminates the physiological responses of largemouth bass to acute heat stress, offering valuable insights into the potential impacts of climate change on freshwater fishes and the sustainability of aquaculture.

Heat stress (HS) has been shown to adversely affect fish livers and can lead to extensive apoptosis. To investigate the relationship between endoplasmic reticulum (ER) stress and HS-induced apoptosis in fish livers, we isolated and cultured primary hepatocytes of largemouth bass, Micropterussalmoides by trypsin method, then established an in-vitro model of liver cells under HS (35 degrees C). The contents of lactic dehydrogenase (LDH) and hydrogen peroxide (H2O2) were determined to evaluate the effects of HS on hepatocyte injury and oxidative stress. RT-qPCR was performed to discover the key genes in unfolded protein response (UPR) pathways involved at different HS duration. ERS inhibitor 4-PBA and IRE1 alpha inhibitor 4 mu 8C were used to further investigate the effects of HS on IRE1 alpha apoptosis pathway in hepatocytes. Results show that HS led to significant increases in the release of LDH, the content of H2O2, and the expressions of oxidative protein folding genes (ero1 alpha and pdi) under HS, suggesting severe hepatocyte injury and oxidative stress happened in heat-stressed largemouth bass hepatocytes. The continuous activation of IRE1 alpha pathway genes (grp78, grp94, atf6, perk, eif2a, atf4, chop, ire1 alpha, traf2, ask1, jnk1, and jnk2) indicated that HS led significantly to ER stress. In particular, the mRNA expression levels of ER stress-related genes (grp78, grp94, atf6, perk, ire1 alpha, chop, jnk1, and jnk2) in the high temperature (HT) +4-PBA group and the HT+4 mu 8C group were significantly down-regulated under HS. After 4 mu 8C treatment, the expression levels of apoptosis-related genes (caspase-2, caspase-3, caspase-6, caspase-7, caspase-8, caspase-9, and caspase-10) and LDH content were significantly decreased, whereas the cell survival rate was significantly increased when given 4-PBA or 4 mu 8C treatment. These findings demonstrate that HS could induce liver apoptosis of largemouth bass through the IRE1 alpha pathway, which may act as a key switch mediating liver apoptosis of largemouth bass under HS

Pikeperch (Sander lucioperca) is a sub-cold water fish species with high aquaculture potential. Its culture is seriously affected by increasing summer temperatures in recent years. Aim to investigate the effects of heat stress on apoptosis, oxidative stress, and the immune response in pikeperch. the fish were heat stressed at 30 °C, 32 °C and 34 °C for 2h respectively, followed by a 48h recovery period. The results showed that as temperature increased, the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in the liver increased significantly. Meanwhile, acute heat stress results in progressive deleterious alterations in liver tissue, especially vascular rupture, blood infiltration, and severe vacuolation at 34 °C. TUNEL staining revealed that the apoptosis level increased significantly with the rising temperature. Acute heat stress significantly induced the mRNA expression of apoptosis-related genes, including tumor suppressor (p53), B-cell lymphoma-2 (bcl-2), bcl-2-associated X (bax), apoptotic protease activating factor-1 (apaf-1), cysteinyl aspartate specific proteinase (caspase-3 and caspase-9), and the expression of p53 was also positively correlated with bax expression and the bax/bcl-2 ratio. Additionally, caspase-3 and caspase-9 activity increased significantly at 34 °C compared with the control group (23 °C). Innate immune genes, including tumor necrosis factor (tnf-α), interleukins (il-7, il-8, il-10 and il-1β), complement 3 (c3) were activated under acute heat stress, and H2O2 content was positively correlated with the expressions of tnf-α and il-1β. After the temperature reached again 23 °C, most measured indexes in heat-stressed groups didn't return to stress-free levels, and liver tissue also didn't return to its normal state in the histopathology. It was found that p53-mediated mitochondrial apoptosis pathway was triggered in pikeperch under acute heat stress, and there may be a vicious cycle between oxidative stress and inflammation. In summary, the present study is helpful to elucidate how acute heat stress mediates liver injury of pikeperch through mitochondrial pathway, inflammation and oxidative stress.

Hatching enzyme (HE) is the most critical enzyme in the process of fish hatching. Pikeperch, Sander lucioperca , is one of economical and ferocious fish with long embryonic incubation and its long and irregular hatching time easily leads to the decrease of its fingerlings due to cannibalism. HE is one of the most important factors that affect the membrane effusion of fish eggs during incubation. The present study aimed to clone HE genes and to reveal the HE expression patterns of pikeperch during its hatching process. In this study, the full-length cDNAs of high choriolytic enzyme gene ( HCE ) and low choriolytic enzyme gene ( LCE ) from pikeperch were cloned and their expressions were performed using qRT-PCR and in situ hybridization. The results showed that the full-length cDNAs of HCE and LCE were comprised of 1189 bp and 1147 bp, respectively, and the open reading frames (ORFs) obtained were 876 bp and 798 bp, encoded proteins of 291 and 265 amino acids, respectively. Phylogenetic analysis showed high homology of HE in Percidae, far from amphibians, birds, and insects. HE genes maintained high expression from body segment appearance stage to hatching stage, and low expression in early embryo and larval stage of pikeperch. HE transcripts were initially detectable at body segment appearance stage in the head region and on the surface of the yolk sac. At hatching stage, strong staining was observed in the whole body from head to the tail. Compared with other fishes, the special spatiotemporal expression pattern of hatching enzyme may be the key factor leading to the irregular hatching time of pikeperch. Our study might enhance our understanding of the hatching mechanism of pikeperch.

Heat stress (HS), an important factor that affects the physiological state of fish, is known to induce apoptosis. To investigate relationships among HS, endoplasmic-reticulum stress (ERS) and apoptosis in fish liver, 72 largemouth bass were randomly exposed to three different water temperatures (33 degrees C, 35 degrees C and 37 degrees C) for 6 h. Then, histological sections and TUNEL assays were analyzed to evaluate the physiological status of the liver. Transcriptome analysis and RT-qPCR were also performed to discover the key pathways involved. HS caused liver tissue damage, enhanced the apoptotic index and up-regulated the expressions of caspase-3, caspase-8, caspase-9 and ER stress marker genes such as grp78 and grp94. The differentially expressed genes (DEGs) under HS were mainly enhanced in 'protein processing in endoplasmic reticulum' pathway. In particular, the PERK and ATF6 pathway genes including perk, eif2a, atf4, chop, bcl-2 and atf6 were significantly up-regulated at 33 degrees C and 35 degrees C, while the IRE1 pathway genes including irel, traf2, askl, jnkl and jnk2 were significantly up-regulated with increasing temperature. These findings suggest that HS induced apoptosis and damage of largemouth bass liver were mainly mediated via ER-stress and the IRE1-signaling pathways. This study, which is the first to reveal that HS-induced ER stress triggers cellular apoptosis in largemouth bass liver, could provide a new approach to the study of HS in fish in the context of global warming.

Pikeperch Sander lucioperca is a cool-water fish considered to be a potential aquaculture species. At present, extreme temperature conditions in summer affect the growth and survival of pikeperch cultured in ponds, indicating that the effects of heat stress on pikeperch merits research attention. In this study, pikeperch were heat stressed at 29 degrees C for up to 48 h. Fish were sampled at different time periods, and changes in gills histopathology and oxidative stress status were determined. The gill transcriptome under heat stress and significantly differentially expressed genes were also analyzed. qPCR was used to detect the expression of antioxidant-related genes and Hsp member family genes in gills of fish subjected to different durations of heat stress. The degree of gill damage increased with prolongation of the heat stress. The activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione reductase (GR) and the malondialdehyde (MDA) content in the gills changed significantly in response to continued heat stress. The expression of 252 genes changed significantly under heat stress: 191 genes were up-regulated and 61 genes were down-regulated. KEGG pathway enrichment analysis showed that multiple pathways were involved in the heat-stress response of the pikeperch but mostly involved lipid metabolism (six pathways), followed by amino acid metabolism (four pathways), carbohydrate metabolism (three pathways), and folding, sorting and degradation. The expression of antioxidant-related genes, including Cu-Zn SOD, Mn SOD and CAT, and the heat shock protein (Hsp) member family genes increased during the early period of heat stress, but decreased in the later period. The overall results indicate that the gills of pikeperch are sensitive to heat stress and pikeperch actively responds to heat stress through regulating the antioxidant system, and the expression of Hsp genes and genes involved in energy metabolism. This study improves our understanding of the effects of heat stress on pikeperch, and reveals the mechanism of the heat-stress response in this species.

Pikeperch (Sander lucioperca L.) is a freshwater fish species of major economic importance in several producer countries. Insufficient information about growth-related genes in pikeperch prevents their breeding through marker-assisted selection (MAS). This study aimed to clone growth-related genes (IGF-I, IGF-II, and GHR) of pikeperch to detect single-nucleotide polymorphisms (SNPs) associated with growth, laying the foundation for MAS in pikeperch. Full-length cDNA sequences of IGF-I, IGF-II, and GHR were isolated using RACE PCR; the cDNA sequences obtained were 883, 1210, and 1995 base pairs, respectively, encoding proteins of 183, 215, and 664 amino acids. The three genes were expressed in all tissues tested, though at especially high levels in the liver. Four SNPs, comprising two in intron 1 of IGF-I, one in intron 3 of IGF-II, and one in the coding region of GHR, were found in a cultured population of pikeperch. Three of the SNPs were successfully genotyped by Kompetitive allele–specific PCR in a randomly mixed group of 298 individuals. The SNP in IGF-II was significantly associated with body weight (SL2-IGF-II-c.544+1111_544+1112delAAinsTC; allele frequency, AA:TC = 52.8:47.2; AA-AA (26), AA-TC (54), and TC-TC (20) genotypes). The fish with genotype TC-TC of SL2-IGF-II-c.544+1111_544+1112delAAinsTC had a significantly greater body weight than fish of genotype AA-AA (P < 0.05). This discovery may provide a useful marker for marker-assisted selection of pikeperch in the future.

为探索池塘循环水条件下不同养殖密度对翘嘴鳜(Siniperca chuatsi)生长的影响,按占池塘面积6％的比例建设养殖单元,剩余94％水体作为尾水净化单元,构建了翘嘴鳜和水生植物(藕、菱)的复合养殖系统.2018年6月,试验设置了20、30、40尾/m2三个养殖密度梯度,每个放养密度组重复3次,对不同养殖密度翘嘴鳜的生长速度、饵料系数、肌肉中营养物质含量进行了测定.结果显示:随着养殖密度的增加,翘嘴鳜平均日增重由4.86 g降至4.19 g,成活率由92.88％降至86.49％,饵料系数由3.77增至4.34.肌肉干物质中共检测出17种氨基酸,总氨基酸(TAA)含量是76.06～80.89 g/100 g、必需氨基酸(EAA)含量是30.39～31.28 g/100 g.肌肉中营养物质包括TAA、EAA、非必需氨基酸(NEAA)含量等均没有随着养殖密度的变化而发生规律性变化.结果表明,池塘循环水条件下适宜养殖密度为30尾/m2.

为了探究白梭吻鲈(Sander lucioperca)精子的结构及活力特点,采用扫描电镜观察其超微结构,并将其置于不同浓度的KCl、CaCl2和葡萄糖溶液中,在光镜下观察不同溶液对其活力的影响.结果 显示:白梭吻鲈精子由头部、中段和尾部3个部分组成,其头部接近于圆形,长约1.8 μm,宽约1.5 μm,主要由细胞核构成,前端无顶体;中段位于细胞核外侧,长约0.4 μm;尾部细长,属于典型的单鞭毛结构.适当浓度的KCl、CaCl2及葡萄糖溶液可以延长精子寿命,最适KCl浓度为75～100 mmol/L,精子快速运动持续时间的峰值为(51.54±7.04)s,精子寿命峰值为(300.34±16.69)s;最适CaCl2浓度为75 mmol/L,精子快速运动持续时间的峰值和寿命峰值分别为(41.07±0.83)、(104.24±4.00)s;最适葡萄糖浓度为150 mmol/L,精子快速运动持续时间的峰值和寿命峰值分别为(45.12±4.03)、(262.60±18.08)s.

工业化生态养殖模式是江苏省农业农村厅大力推广的生态高效健康养殖模式,宿迁市自2016年推广以来,全市已建成养殖系统水槽315条,近7万米2,养殖草鱼、鳜鱼、鲫鱼、加州鲈等品种.笔者自2016年5月以来全程参与了董氏家庭农场系统设计、水槽建设、苗种放养、养殖管理和成鱼收获.2018年1月,由于系统改建需要对生态养殖系统进行清塘,所有养殖水产品上市销售,现对池塘工业化生态养殖系统全周期养殖经济效益分析如下.

Pikeperch (Sander lucioperca) is an economically important cool-water fish. In recent years, its cultivation has become threatened by higher temperatures in summer. We previously investigated the effects of heat stress on pikeperch liver under different temperatures, but the molecular mechanism of the heat-stress response is still unknown. This study applied consistent heat stress (29 degrees C, 0-48 h) to pikeperch juveniles, and a transcriptomic profile of pikeperch liver under heat stress (29 degrees C, 0-48h) was performed by RNA-Seq. The antioxidant status, changes in liver histology, and antioxidant gene expression at different time points were examined. We identified 403 differentially expressed genes (DEGs), many of which were enriched in KEGG pathways, including protein processing in endoplasmic reticulum (ER), insulin signaling, and immune-related pathways. Among these, the most significant heat-stress-related pathway was protein processing in ER, indicating that this pathway is critical for the heat-stress response. After consistent heat stress at 29 degrees C, the total antioxidant capacity (T-AOC), the activities of total superoxide dismutase (T-SOD) and catalase (CAT), and the mRNA expression of manganese SOD (Mn-SOD), CAT, and glutathione peroxidase 1 and 7 (GPx1 and GPx7) in the treated groups showed the same trend of first increasing and then decreasing. Levels of malondialdehyde (MDA) content did not show significant differences between samples at 0 h and 3 h, but significantly increased by 6 h, and thereafter decreased. The liver tissue was normal at 0 h (29 degrees C); however, it suffered histological damage with increased duration of the heat stress. Above all, heat stress at 29 degrees C seemed to cause oxidative damage and dysfunction in pikeperch liver between 3 h and 48 h. The present results indicate that pikeperch have the capacity to defend against heat stress and maintain relative balance of oxidation-reduction reactions mainly through activating the antioxidant system, protein processing in ER, the insulin-signaling pathway, and immune-related pathways.

The pikeperch Sander lucioperca is an economically important freshwater species that is currently threatened by higher summer temperatures caused by global warming. To clarify the physiological state of pikeperch reared under relatively high temperatures and to acquire valuable biomarkers to monitor heat stress in this species, 100 fish were subjected to five different temperature treatments, ranging from 23 °C (control) to 36 °C. The physiological and biochemical indexes of liver and blood were determined, and heat-shock cognate 70 kDa protein (Hsc70) mRNA expression profiles were analyzed. The results showed that the activities of superoxide dismutase, catalase, and glutathione peroxidase in heat-stressed pikeperch first increased and then decreased, exhibiting peaks at 34 °C, 28 °C, and 28 °C, respectively. The level of thiobarbituric acid-reactive substances (TBARS) in all experimental groups was significantly higher than that of the control. The numbers of red blood cells, the packed-cell volume, and the contents of hemoglobin were significantly higher in the 34 °C and 36 °C treatment groups. Under heat stress, the albumin, cholesterol, and triglycerides contents decreased with increasing temperatures. Real-time fluorescence-based quantitative RT-PCR showed that Hsc70 mRNA levels increased in all eight of the tested tissues under heat stress. Expression reached maximum levels at 34 °C in the muscle, heart and gill tissues, and at 36 °C in the other five tissues. These results demonstrate that several physiological and biochemical phenotypes, such as oxidative stress, antioxidant enzymes and molecular chaperones, could be important biomarkers of heat stress in pikeperch, and are potentially valuable to uncover the mechanisms of heat-stress responses in fish.

研究白梭吻鲈在4℃冷藏条件下的品质变化.鲜活白梭吻鲈宰杀后去鳞、去尾、去内脏,将头部和切块的肌肉分装并储存于4℃冰箱中.在第0、3、6、9、12、15天时取样分析,以感官评价(quality index,QI值)、硫代巴比妥酸值(thiobarbituric acid,TBA)、 可挥发性盐基氮值(total volatile basic-nitrogen,TVB-N)、pH值和菌落总数(total viable count,TVC)作为评估指标.结果表明:随着储藏时间延长,感官评价值(QI值)、硫代巴比妥酸值、可挥发性盐基氮和菌落总数均呈现逐步上升的趋向,而pH值表现为先下降后上升.第9天时QI分值为8.7,TBA值为0.64 mg/100 g,TVB-N值为19.64 mg/100 g,TVC值为5.08 lgCFU/g,各指标虽未超出但已接近食品安全限值,此时白梭吻鲈肌肉已经腐败变质,将不再具可食用性.

The genetic paradox of biological invasions is complex and multifaceted. In particular, the relative role of disparate propagule sources and genetic adaptation through postintroduction hybridization has remained largely unexplored. To add resolution to this paradox, we investigate the genetic architecture responsible for the invasion of two invasive Asian carp species, bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix) (bigheaded carps) that experience extensive hybridization in the Mississippi River Basin (MRB). We sequenced the genomes of bighead and silver carps (~1.08G bp and ~1.15G bp, respectively) and their hybrids collected from the MRB. We found moderate-to-high heterozygosity in bighead (0.0021) and silver (0.0036) carps, detected significantly higher dN/dS ratios of single-copy orthologous genes in bigheaded carps versus 10 other species of fish, and identified genes in both species potentially associated with environmental adaptation and other invasion-related traits. Additionally, we observed a high genomic similarity (96.3% in all syntenic blocks) between bighead and silver carps and over 90% embryonic viability in their experimentally induced hybrids. Our results suggest intrinsic genomic features of bigheaded carps, likely associated with life history traits that presumably evolved within their native ranges, might have facilitated their initial establishment of invasion, whereas ex-situ interspecific hybridization between the carps might have promoted their range expansion. This study reveals an alternative mechanism that could resolve one of the genetic paradoxes in biological invasions and provides invaluable genomic resources for applied research involving bigheaded carps.

为探究热胁迫对白梭吻鲈(Sander lucioperca)鳃组织结构及抗氧化指标的影响,以23℃为对照组,设置28℃、31℃、34℃和36℃共计4个热胁迫组,测定不同温度胁迫对白梭吻鲈鳃中超氧化歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GPX)活性和丙二醛(MDA)等抗氧化指标以及鳃组织结构的影响.结果 显示,28℃组鳃小片发生充血,31℃组部分鳃小片末端卷曲变形、上皮细胞水肿,34℃组鳃小片变形加重,且有少量融合,上皮细胞水肿加重、明显隆起,鳃小片之间粘液细胞肥大、增生,36℃组相邻鳃小片大量融合且严重变形,卷曲混乱排列,大量上皮细胞坏死、脱落,鳃丝粘液细胞增生、肥大;随着胁迫温度升高,鳃中SOD、CAT、GPX、MDA均整体呈现先升高、后降低的变化趋势,且在36℃时显著下降,表明热胁迫对白梭吻鲈鳃组织有损伤,且随着热胁迫温度的升高,其鳃受损情况越发严重.

该文在实验室条件下,研究了不同温度(20、24、26、28、32 ℃)对体质量(19.39±2.06)g和(33.41±2.96)g梭鲈幼鱼耗氧率(Ro)、排氨率(RN)及窒息点的影响.结果显示:水温20～32℃时,2种规格的梭鲈幼鱼耗氧率、排氨率和窒息点都随着温度的上升而上升;2种规格的梭鲈幼鱼耗氧率差异具统计学意义(P＜0.05);RO和RN与温度(T)之间的关系符合指数函数关系,体质量(19.39±2.06)g方程分别为:Ro=0.0573e0.0459T(R2=0.9748),RN=16.62e0.0356T(R2=0.9890);(33.41±2.96)g方程分别为:Ro=0.0154e0.0866T(R2=0.9623),RN=4.511e0.0665T(R2=0.8697);梭鲈幼鱼的窒息点在0.830-1.100 mg/L.结果表明,不同温度对两种体质量的梭鲈幼鱼耗氧率影响显著(P＜0.05),但对排氨率和窒息点有一定影响.