Search Results (16)

Triploid fish have attracted considerable attention in aquaculture because of their sterility and rapid growth. In this study, a novel allotriploid fish (WA, 3n = 150) was obtained through distant hybridization of a female diploid hybrid fish (WR-II, 2n = 100) with a male allotetraploid fish (4nAT, 4n = 200). The measurable traits of WA exhibit significant differences from WR-II and its original parents (white crucian carp (WCC) and red crucian carp (RCC)). WA muscles exhibited higher protein, fat, and essential amino acid levels but lower moisture. Furthermore, WA enhanced growth performance and muscle hypertrophy compared to WCC and RCC. The transcriptomes and metabolomics of the muscle tissues of WA, WCC, and RCC were analyzed. In total, 3889 and 1863 differential expressed genes (DEGs) were identified in WA vs. WCC and WA vs. RCC, respectively. These DEGs were mainly enriched in pathways related to amino acid biosynthesis and oxidative phosphorylation. In total, 421 and 304 differential metabolites (DMs) were identified in WA vs. WCC and WA vs. RCC, respectively. These DMs were mainly enriched in the pathways related to glycerophospholipid and fatty acid metabolism. Integrated transcriptomic and metabolomic analyses revealed that the expression patterns of acta1, myh, myog, and aldoa were associated with changes in the abundance of oleoyl ethanolamide, betaine, inosine, docosahexaenoic acid (DHA), and PC (38:6), suggesting their potential involvement in the enhanced growth performance of WA. This study provides a potential genetic resource for aquaculture and identifies molecular features associated with enhanced growth performance in this allotriploid fish. Full article

This study provides a systematic and multidimensional evaluation of flesh quality differences between triploid (T-PZ) and allotetraploid (A-PZ) Pengze crucian carp, addressing a significant gap in genetic improvement of this economically important aquaculture species. By integrating proximate composition analysis, detailed amino acid and fatty acid profiling, volatile flavor compounds, texture characteristics, and non-targeted muscle metabolomics, we delineated the distinct quality attributes associated with each cytotype. The results showed that T-PZ possessed significantly higher crude protein and histidine content, along with a superior flavor profile characterized by lower relative levels of fishy odor-associated aldehydes such as hexanal, heptanal, and nonanal. In contrast, A-PZ exhibited significantly elevated crude lipid, total fatty acid, SFA, MUFA, PUFA, and EPA + DHA contents; a higher essential amino acid index; and improved tenderness indicated by significantly lower hardness and chewiness. Metabolomic analysis identified 216 significantly different metabolites, notably enriched in key pathways including glycine, serine, and threonine metabolism; arginine biosynthesis; and glycerophospholipid metabolism. These comprehensive findings elucidate the complementary nutritional and sensory strengths of the two ploidy forms, thereby establishing a crucial scientific foundation for targeted, quality-driven breeding programs aimed at optimizing flesh quality in Pengze crucian carp for the aquaculture industry. Full article

Allotetraploid fish produced by distant hybridization are valuable germplasm for the mass production of sterile triploids. The allotetraploid crucian–carp hybrid (4nAT, 4n = 200) is derived from the intergeneric cross between a female red crucian carp (Carassius auratus red var., 2n = 100) and a male common carp (Cyprinus carpio L., 2n = 100). However, after 33 successive generations, this lineage faces a critical bottleneck in maintaining male fertility. The present study aimed to develop new biomarkers for testicular development and characterize the associated functional gene expression profile in 4nAT. Following whole-genome resequencing and selection signature analysis of 15 male 4nAT individuals from each of the high-development group (HDG) and low-development group (LDG), ZSWIM7 (Zinc Finger SWIM-Type Containing 7), a gene implicated in reproductive development, was selected as a candidate for further fertility association studies. Seven SNPs were screened in the coding region of ZSWIM7 of 70 4nAT males; among these, SNP3 (c.23T/C) exhibited a significant correlation between genotypes and testicular development: individuals with the CT genotype showed a higher gonadosomatic index (1.17 ± 0.68 vs. 0.65 ± 0.50) and greater counts of mature spermatozoa (2537.67 ± 283.95 vs. 341.56 ± 121.66) compared to those with the TT genotype. Further quantitative PCR and immunofluorescence assays demonstrated that ZSWIM7 was highly expressed in the testis and specifically localized to the nuclei of early meiotic primary spermatocytes. Collectively, these results establish ZSWIM7 as a promising biomarker for 4nAT testicular development, offering a potential molecular tool for maintaining male fertility in allotetraploid fish breeding. Full article

Cold stress poses a critical threat to fish survival by triggering metabolic dysfunction, oxidative damage, immune suppression, and apoptosis. However, hybrid polyploid fish triploid crucian carp (3nRCR, 3n = 150) demonstrate superior stress tolerance. In this study, we investigated the cold adaptation mechanisms in different ploidy cyprinid fishes: triploid crucian carp compared to its diploid improved red crucian carp (Carassius auratus red var., RCC, 2n = 100, ♀) and improved allotetraploid (4nAT, 4n = 200, ♂) progenitors. Under controlled cooling, 3nRCR lost equilibrium at a significantly lower temperature (3.2 °C) than RCC (4.0 °C) and 4nAT (4.5 °C), confirming its superior enhanced cold resistance. Histological examination revealed minimal tissue damage in 3nRCR, characterized by reduced gill inflammation and cellular apoptosis. Transcriptomics revealed triploid-specific molecular strategies: 3nRCR uniquely activated retinol metabolism and metabolic rewiring (arginine/proline metabolism, oxidative phosphorylation). Notably, in the immune-related NLR signaling pathway, both nlrp1 and nlrp3 (key inflammasome components) were significantly downregulated in 3nRCR (p < 0.01). In contrast, genes involved in endoplasmic reticulum (ER) stress response, including chop and nrf2, were markedly upregulated, indicating a reinforced cellular stress resolution mechanism absent in both RCC and 4nAT. Our results demonstrate that triploid cold adaptation is orchestrated through a balanced interaction among mitochondrial apoptosis, ER stress, and inflammasome pathways. These findings provide novel insights into hybrid polyploid adaptation mechanisms and targets for cold-resilient aquaculture breeding. Full article

Carassius auratus var. suogu, an endemic fish in southern China, is a natural triploid crucian carp mutant. In this study, the characteristics of mitochondrial DNA sequences were analyzed to understand their taxonomic status and genetic background at the gene level. The complete mitochondrial genome of C. auratus var. suogu (length, 16,580 bp) comprises 37 genes (13 protein-coding genes, 22 transfer RNA (tRNAs) genes, and 2 ribosomal RNA (rRNAs) genes) and a non-coding control region. The RSCU of the mtDNA of Carassius was similar. Ka/Ks analyses showed the ND4 gene had the highest evolutionary rate. Moreover, the whole mitogenome sequences and D-loop region were employed to examine phylogenetic relationships among C. auratus var. suogu and other closely related species. The result indicated that Carassius auratus suogu var clustered with Carassius auratus auratus and divided Carassius into four clades, providing new insights and data support for the taxonomic status of Carassius. Full article

Background: Owing to the progressive rise in saline waters globally, resulting in detrimental impacts on freshwater aquaculture, the underlying molecular distinctions governing the response to alkaline stress between diploid and triploid crucian carp remain unknown. Methods: This investigation explores the effects of 20 and 60 mmol NaHCO₃ stress over 30 days on the gills of diploid and triploid crucian carp, employing histological, biochemical, and multi-omic analyses. Results: Findings reveal structural damage to gill lamellas in the examined tissue. Diploid crucian carp exhibit heightened activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and alkaline phosphatase (AKP), alongside lower malondialdehyde (MDA) and urea nitrogen (BUN) levels compared to triploid counterparts. Metabolomic investigations suggest alterations in purine metabolism, lipid metabolism, sphingolipid metabolism, and aminoglycan and nucleotide sugar metabolism following NaHCO₃ exposure. Transcriptomic data indicate differential expression of genes associated with nitrogen metabolism, complement and coagulation cascades, IL-17 signaling pathways, and Toll-like receptor signaling pathways. Conclusions: Overall, NaHCO₃-induced stress leads to significant gill tissue damage, accompanied by reactive oxygen species (ROS) production causing oxidative stress and disruptions in lipid metabolism in crucian carp. Furthermore, an inflammatory response in gill cells triggers an immune response. Diploid crucian carp exhibit superior antioxidant and immune capacities compared to triploid counterparts, while also displaying reduced inflammatory responses in vivo. Notably, diploid carp efficiently excrete excess BUN through purine metabolism, mitigating protein metabolism and amino acid imbalances caused by BUN accumulation. This enables them to allocate less energy for coping with external environmental stress, redirecting surplus energy toward growth and development. The above results indicate that diploid organisms can better adapt to saline–alkaline environments. Overall, this study provides novel perspectives into species selection of crucian carp of different ploidy in saline–alkaline waters. Full article

Objectives: The salinization of the water environment worldwide is increasing, which has brought great challenges to the sustainability of fish farming of aquatic animals. Methods: Three NaHCO₃ concentration groups (0 mmol/L, 20 mmol/L, and 60 mmol/L) were set up in this study to investigate growth and metabolic differences between diploid and triploid crucian carp under saline-alkaline stresses. Purpose: This study utilized UPLC-QTOF/MS metabolomics to analyze significant metabolites and metabolic pathways in the serum of diploid and triploid crucian carp, exposing them to different NaHCO₃ concentrations in saline-alkaline habitats, elucidating the mechanism of their metabolic differences. Results: Results revealed that in the CA20 group, diploid and triploid crucian carp shared 69 differential metabolites, primarily enriched in pathways such as sphingolipid metabolism, glycerophospholipid metabolism, and linoleic acid metabolism. In the CA60 group, 46 differentially metabolites (DMs) were identified, mainly enriched in pathways such as linoleic acid metabolism, unsaturated fatty acid biosynthesis and sphingolipid metabolism. Conclusions: The analysis indicated that under different carbonate-saline-alkaline concentrations, diploid and triploid crucian carp primarily enriched in metabolic pathways such as glycerophospholipid metabolism, sphingolipid metabolism, and unsaturated fatty acid biosynthesis. With increasing carbonate-alkaline concentrations, hemolytic phospholipids associated with cell apoptosis were significantly upregulated and sphingolipid metabolism related to inflammation was more significantly enriched in triploid crucian carp, indicating that triploid crucian carp exhibited significant sensitivity to high carbonate-saline-alkaline stress and poorer carbonate-saline-alkaline tolerance. The results of this study provided a scientific theoretical basis for the later cultivation and aquaculture research of saline-alkaline-tolerant fish species. Full article

Estrogen is an essential sex steroid that functions in numerous biological systems including female reproduction, neuroendocrine, vascular, skeletal, and immune systems. The synthesis of estrogen is controlled by the rate-limiting enzyme, which has been confirmed to exist in two different forms, named brain aromatase and ovary aromatase, and encoded by cyp19a1a and cyp19a1b respectively in teleosts. However, existing studies have primarily focused on the expression and function of cyp19a1b in the brain and cyp19a1a in the gonad, the roles of cyp19a1b in the female gonad of teleosts are largely unknown. In our previous study, we cloned the full length of the cyp19a1b gene from a natural triploid teleost Qi River crucian carp (Carassius auratus), andthe spatial and temporal expression patterns of cyp19a1b mRNA were detected. To further clarify the roles of cyp19a1b in the ovarian differentiation of Qi River crucian carp, we produced a polyclonal antibody of Cyp19a1b in this study. Western blotting results showed that Cyp19a1b was mainly expressed in the brain and then in the ovary, heart, liver, and muscle. During embryogenesis, Cyp19a1b was abundantly expressed in the neurula stage. Immunohistochemistry demonstrated that Cyp19a1b was expressed in the radioactive glial cells (RGCs) of the brain from 20 days after hatching (dah) and the somatic cells of the ovaries from 30 dah, the critical period of ovarian differentiation in Qi River crucian carp. With the treatment of letrozole, an inhibitor of the aromatase, the expression of Cyp19a1b was downregulated both in the brain and gonad. Our results suggested that Cyp19a1b might be involved in the development of the nervous system and also participate in the ovarian differentiation of Qi River crucian carp. Full article

A 56-day feeding trial was conducted to evaluate the effect of different dietary protein sources on the growth performance, muscle flavor substances, and quality structure of Triploid Crucian Carp. Three isonitrogenous (32.00%), isolipidic (8.00%), and isoenergetic (18.00 MJ kg⁻¹) practical diets were formulated. These diets consisted of fishmeal as the animal-derived protein source (AP), a combination of soybean meal and rapeseed meal as the plant-derived protein source (PP), and a mixture of fishmeal, soybean meal, and rapeseed meal as the mixed protein source (MP). Each diet was randomly assigned to triplicate tanks of fish and each tank was stocked with 25 fish (11.5 ± 0.4 g). The fish were fed until apparent satiation twice a day. The results showed a significant enhancement in the growth performance of Triploid Crucian Carp in the AP group compared with both the MP and PP groups (p < 0.05). Dietary plant derived protein can remarkably reduce the crude lipid content and increase the moisture content of the whole body and the dorsal muscle (p < 0.05). The antioxidant ability of fish in the PP group and MP group was better than that in the AP group (p < 0.05). Regarding free amino acids composition of muscle, the contents of glycine, methionine, and lysine were significantly enhanced in the AP group, while the histidine content was significantly increased in the PP group (p < 0.05). In terms of texture, dietary plant protein significantly improved the muscular hardness, gumminess, and chewiness. The activities of intestinal trypsin and alkaline phosphatase (ALP) of fish in the PP group were significantly higher than that in the AP group (p < 0.05). The expression levels of hepatopancreas TOR and IGF1 genes in the PP group were significantly higher than that in the MP group (p < 0.05). The present results indicate dietary fishmeal significantly improved the growth performance and muscular flavor glycine content, while dietary plant-based protein increased crude protein content, antioxidant ability, and muscular texture performance of Triploid Crucian Carp. Full article

The aim of this study is to investigate the effect of dietary protein levels on flesh quality, oxidative stress, and autophagy status in the muscles of triploid crucian carp (Carassius carassius triploid), and the related molecular mechanisms. Six experimental diets with different protein levels (26%, 29%, 32%, 35%, 38%, 41%) were formulated. A total of 540 fish with an initial weight of 11.79 ± 0.09 g were randomly assigned to 18 cages and six treatments with three replicates of 30 fish each for 8 weeks feeding. It could be found that the whole-body ash content significantly increased in high protein level groups (p < 0.05). The 29% dietary protein level group exhibited the highest muscle moisture, although there was an inconspicuous decrease in the chewiness of the muscles when compared with the other groups. The dietary protein level influenced the content of free amino acids and nucleotides, especially the content of flavor amino acids, which exhibited an increasing tendency along with the increasing protein level, such as alanine and glutamic acid, while the flavor nucleotides showed different fluctuation trends. Moreover, the genes related to muscle development were shown to be influenced by the dietary protein level, especially the expression of MRF4, which was up-regulated with the increasing dietary protein levels. The 29% dietary protein level promoted the majority of analyzed muscle genes expression to the highest level when compared to other dietary levels, except the Myostain, whose expression reached its highest at 38% dietary protein levels. Furthermore, the effect of dietary protein levels on antioxidant signaling pathway genes were also examined. High protein levels would boost the expression of GSTα; GPX1 and GPX4α mRNA expression showed the highest level at the 32% dietary protein group. The increasing dietary protein level decreased both mRNA and protein expressions of Nrf2 by up-regulating Keap1. Autophagy-related gene expression levels reached the peak at 32% dietary protein level, as evidenced by a similar change in protein expression of FoxO1. In summary, muscle nutritional composition, antioxidative pathways, and autophagy levels were affected by the dietary protein levels. A total of 29–32% dietary protein level would be the appropriate level range to improve muscle quality and promote the antioxidant and autophagy capacity of triploid crucian carp muscles. Full article

Fish by-products are rich in collagen. Hydrolyzed collagen derived from fish by-products was used to replace fish meal to evaluate the effects on muscle quality and glycolipid metabolism of juvenile triploid crucian carp. A total of 240 juvenile fish with body weight of 10.01 ± 0.02 g were divided into four groups and fed four diets for 66 days: fish meal (FM) replaced with hydrolyzed collagen (HC) in 0% (Control), 2% (2% HC), 4% (4% HC), and 6% (6% HC), respectively. The results were as follows: The increased proportion of fish meal replaced with hydrolyzed collagen linearly and quadratically decreased the specific growth rate (SGR) of triploid crucian carp (p < 0.05). Compared with the control group, the SGR and intestinal α-amylase, trypsin and lipase activities in the 4% and 6% HC groups significantly decreased (p < 0.05), while there was no significant difference between the control and 2% HC groups (p > 0.05). Total umami amino acids content, chewiness and myofiber density of muscle in the 4% and 6% HC groups, as well as the essential fatty acids content in all HC groups increased significantly (p < 0.05). All HC groups significantly increased the serum glutathione peroxidase (GSH-Px) activity and decreased the serum malondialdehyde (MDA) content (p < 0.05). When the replacement amount reached 4%, the serum glucose and liver glycogen content, the liver and serum triglyceride (TG) content, and serum total cholesterol (T-CHO) content were significantly reduced (p < 0.05). In addition, the expression levels of insulin-like growth factor-1 (IGF-1) of the liver in all HC groups and lipolysis-related genes (lipoprotein lipase (LPL), carnitine O-palmitoyltransferase 1 (CPT 1) and hydroxyacyl-coenzyme A dehydrogenase (HADH)) of the liver in the 6% of HC group increased significantly (p < 0.05), and the expression levels of lipogenesis-related genes (fatty acid synthase (FAS) and sterol regulatory element-binding protein 1 (SREBP 1)) of the liver in the 4% HC and 6% HC groups decreased significantly (p < 0.05). In conclusion, the replacement of 2% fish meal with hydrolyzed collagen had no negative effects on the growth of triploid crucian carp, while the replacement of 4% fish meal with hydrolyzed collagen decreased SGR, but improved the muscle quality and decreased glycolipid levels. The maximum proportion of hydrolyzed collagen replacing fish meal should not exceed 4%. Full article

Kidney-type glutaminase, encoded by the gls1 gene, plays a critical role in glutamate production and improvement of meat flavor. In this study, a gls1 gene encoding 595 amino acids was cloned from triploid crucian carp (Carassius auratus) (TCC) and showed a high similarity with the gls1 gene found in Cyprinus carpio, Sinocyclocheilus rhinocerous and Puntigrus tetrazona. Comparing the abundance of gls1 in different tissues, we found its expression level in the brain and liver were significantly higher than that in heart, gut, kidney, spleen and muscle. gls1 expression in the brain reached the highest value. In addition, the expression levels of gls1 also appeared different in diurnal variation, with the highest expression seen at 9:00, while it was low at 3:00, 6:00, 15:00 and 24:00. Furthermore, dietary regulation of gls1 expression was investigated in our study. In each feeding trial, each diet was randomly assigned to triplicate tanks. Fish were fed one of the tested diets up to satiation twice daily. The results showed that gls1 expression increased in 32% protein group and decreased in 35–41% protein group. The results of different protein source experiments showed that the expression of gls1 gene in the mixed protein group (the control group) was significantly higher than that in the fish meal and soybean meal groups. Glutamate treatment revealed that appropriate concentrations (0.10 mg/mL in vivo and 2.00% in vitro) of glutamate remarkably improved the expression of gls1. Besides, diets supplemented with 0.80–1.60% lysine-glutamate dipeptide exhibited a down regulatory impact on gls1 expression. In conclusion, this study demonstrated that the expression of gls1 in TCC was increased by 32% protein diet, mixed protein source diet and diet with 2.00% glutamate concentration, while decreased by 0.80–1.60% lysine-glutamate dipeptide. The findings of this study provide a reference for the regulation of gls1 and have a potential application in the optimization of dietary formula in aquaculture. Full article

Liver Kinase B1 (LKB1) is a serine/threonine kinase that can regulate energy metabolism and skeletal muscle growth. In the present study, LKB1 cDNA of triploid crucian carp (Carassius auratus) was cloned. The cDNA contains a complete open reading frame (ORF), with a length of 1326 bp, encoding 442 amino acids. Phylogenetic tree analysis showed that the LKB1 amino acid sequence of the triploid crucian carp had a high sequence similarity and identity with carp (Cyprinus carpio). Tissue expression analysis revealed that LKB1 was widely expressed in various tissues. LKB1 expressions in the brain were highest, followed by kidney and muscle. In the short-term LKB1 activator and inhibitor injection experiment, when LKB1 was activated for 72 h, expressions of myogenic differentiation (MyoD), muscle regulatory factor (MRF4), myogenic factor (MyoG) and myostatin 1 (MSTN1) were markedly elevated and the content of inosine monophosphate (IMP) in muscle was significantly increased. When LKB1 was inhibited for 72 h, expressions of MyoD, MyoG, MRF4 and MSTN1 were markedly decreased. The long-term injection experiment of the LKB1 activator revealed that, when LKB1 was activated for 15 days, its muscle fibers were significantly larger and tighter than the control group. In texture profile analysis, it showed smaller hardness and adhesion, greater elasticity and chewiness. Contrastingly, when LKB1 was inhibited for 9 days, its muscle fibers were significantly smaller, while the gap between muscle fibers was significantly larger. Texture profile analysis showed that adhesion was significantly higher than the control group. A feeding trial on triploid crucian carp showed that with dietary lysine-glutamate dipeptide concentration increasing, the expression of the LKB1 gene gradually increased and was highest when dipeptide concentration was 1.6%. These findings may provide new insights into the effects of LKB1 on fish skeletal muscle growth and muscle quality, and will provide a potential application value in improvement of aquaculture feed formula. Full article

Glutamine synthetase (GS) is a key enzyme that catalyzes the synthesis of glutamine from glutamate, which plays a role in the promotion of muscle cell growth and in improving the flavor of meats. In this study, a GS gene encoding 371 amino acids was cloned from triploid crucian carp and showed the highest level of similarity with the GS gene found in Cyprinus carpio. Meanwhile, GS was differentially expressed in different tissues, and its day–night expression changes showed obvious oscillation. Additionally, the effects of glutamate and glutamine on GS expression in muscle cells were investigated in vitro and in vivo. We found that its expression was obviously increased due to high levels of glutamate (2 mg/mL) but decreased by glutamine in vitro. However, it was significantly promoted by glutamate and glutamine in vivo, with an optimal concentration of 2%. Furthermore, the use of lysine–glutamate dipeptides as feed additives also had a positive influence on GS expression (the optimal concentration is 0.8%). Finally, we explored the effects of different protein levels and sources on the expression of GS, and the results demonstrated that GS had the highest expression at the 35% protein level, but no significant differences were observed in the different protein sources between the fish meal diet (FM) and the mixed diet comprising soybean meal and rapeseed meal (SM). This study sheds new light on the regulation of GS in teleost fish and provides new perceptions and strategies for the formulation of high-quality feed for triploid crucian carp. Full article

AlaSerCys Transporter 2 (ASCT2), encoded by the SLC1A5 gene, plays an important role in the absorption of glutamine. In this study, the full-length cDNA sequence of ASCT2 was cloned from triploid crucian carp. It encodes 539 amino acid residues and a stop codon. Phylogenetic analysis revealed that the sequences of the ASCT2 ORF region in cyprinid fishes shared high sequence homology. Comparing the abundance of ASCT2 in different tissues, we found its expression level in muscle was significantly higher than that in intestine (p < 0.05). In addition, the expression levels of ASCT2 also appeared different in diurnal variation. Then we found the addition of 2.5% glutamate in a feeding diet significantly increased the expression levels of ASCT2 in intestine and muscle (p < 0.05). However, in glutamine experiments, the muscle showed the highest expression level of ASCT2 when fish were fed the diet containing 3.0% glutamine (p < 0.05). In vitro, ASCT2 was sensitive to glutamine and its expression level appeared down-regulated when the addition of glutamine was added to 0.1 mg/mL. Finally, we found that the diet with 29% protein level significantly increased the expression level of ASCT2 in intestine (p < 0.05). Nevertheless, different protein sources (fish meal and soybean meal) had no significant effect on the expression levels of ASCT2 in intestine and muscle (p > 0.05). These results provided data for the study of ASCT2 in triploid crucian carp regulated by feeding nutrition, which had a potential application in improving feed formulation in aquaculture. Full article