Chinese Longsnout Catfish Research Articles

Influence of Liquid Nitrogen Pre-Freezing and Drying Methods on the Collagen Content, Physical Properties, and Flavor of Fish Swim Bladder.

Fish swim bladder (FSB) is a type of traditional nutraceutical, but the lack of high-quality drying methods limits its premium market development. In order to obtain optimal-quality dried FSBs from Chinese longsnout catfish, the effects of liquid nitrogen pre-freezing (LNF) and drying on the physical properties and flavor of FSB were evaluated. Four methods were used for FSB drying, including natural air-drying (ND), hot-air-drying (HD), LNF combined with freeze-drying (LN-FD), and LNF combined with HD (LN-HD). Color, collagen content, rehydration ratio, textural properties, and flavor characteristics (by GC-IMS, E-nose, and E-tongue) were measured to clarify the differences among four dried FSBs. The results showed that ND cannot effectively remove moisture from FSB as the final product showed a stronger sourness in taste. HD led to a decrease in the collagen content and the collapse of the fiber structure in FSB. Compared to HD, LN-HD showed a higher collagen content (0.56 g/g) and a different flavor fingerprint. FSB treated by LN-FD had better physical qualities in terms of an attractive color, a high collagen content (0.79 g/g), low shrinkage, a higher rehydration ratio (2.85), and a soft texture, while also possessing richer characteristic flavors. The application of LN-FD may help the optimization of the nutrition level, rehydration ability, mouthfeel, and flavor of dried FSB.

Hypermucoviscous Multidrug-Resistant Klebsiella variicola Strain LL2208 Isolated from Chinese Longsnout Catfish (Leiocassis longirostris): Highly Similar to Human K. variicola Strains.

Outbreaks of bacterial diseases occur in farmed Chinese longsnout catfish (Leiocassis longirostris). Due to limited information on aquatic Klebsiella variicola-infected animals, this study aimed to identify strain LL2208 isolated from diseased L. longirostris, determine its biological features, and evaluate its risk to public health. Strain LL2208 was tested for molecular identification, challenge, string, biofilm formation, and antimicrobial susceptibility. Furthermore, the whole genome of the strain was sequenced and analyzed. Based on molecular identification, strain LL2208 was identified as K. variicola. Artificial infection showed that this strain was moderately virulent to L. longirostris with an LD50 = 7.92 × 107 CFU/mL. Antibiotic sensitivity tests showed that this strain was resistant to penicillins, macrolides, aminoglycosides, amphenicols, glycopeptides, and lincosamide, indicating multidrug resistance. Strain LL2208 has a genome size of 5,557,050 bp, with a GC content of 57.38%, harboring 30 antimicrobial resistance genes and numerous virulence-related genes. Its molecular type was ST595-KL16-O5. Collinearity analysis showed that strain LL2208 was highly similar to the human-derived K. variicola strain. In conclusion, the multidrug-resistant and virulent K. variicola strain LL2208 was isolated from fish and may have originated from humans. These results provide a foundation for further studies on the transmission of K. variicola between humans and aquatic animals.

The Chinese longsnout catfish genome provides novel insights into the feeding preference and corresponding metabolic strategy of carnivores.

Fish show variation in feeding habits to adapt to complex environments. However, the genetic basis of feeding preference and the corresponding metabolic strategies that differentiate feeding habits remain elusive. Here, by comparing the whole genome of a typical carnivorous fish (Leiocassis longirostris Günther) with that of herbivorous fish, we identify 250 genes through both positive selection and rapid evolution, including taste receptor taste receptor type 1 member 3 (tas1r3) and trypsin We demonstrate that tas1r3 is required for carnivore preference in tas1r3-deficient zebrafish and in a diet-shifted grass carp model. We confirm that trypsin correlates with the metabolic strategies of fish with distinct feeding habits. Furthermore, marked alterations in trypsin activity and metabolic profiles are accompanied by a transition of feeding preference in tas1r3-deficient zebrafish and diet-shifted grass carp. Our results reveal a conserved adaptation between feeding preference and corresponding metabolic strategies in fish, and provide novel insights into the adaptation of feeding habits over the evolution course.

Genetic Diversity and Population Structure of Chinese Longsnout Catfish (Leiocassis longirostris) Using Microsatellite DNA Markers

The Chinese longsnout catfish (Leiocassis longirostris) is an economically important freshwater fish in China; however, its wild resources have declined dramatically in recent decades. Understanding the genetic structure of Chinese longsnout catfish populations is crucial to guide breeding programs and fishy restoration. In this study, 15 highly polymorphic microsatellite DNA loci were used to evaluate its genetic diversity and population structure. Chinese longsnout catfish populations show high genetic diversity; they do not show significant genetic differentiation or systematic geographic pattern of variation. From the upper to the lower reaches of the Yangtze River, the genetic diversity of Chinese longsnout catfish populations showed an increasing trend. The Gezhouba and Three Gorges dams, which physically divide the Yangtze River into upstream and mid-downstream sections, did not contribute to the genetic differentiation of Chinese longsnout catfish populations. Hence, the source of broodstock is not critical for within-river breeding programs and stock enhancement to restore the wild population. In addition, possible effects of dams on differentiation among populations are crucial and long-term evaluation is essential.

Identification of genes related to growth from transcriptome profiles of the muscle and liver of Chinese longsnout catfish (Leiocassis longirostris)

The Chinese longsnout catfish (Leiocassis longirostris) is a commercially important freshwater fish species in China. To understand the molecular mechanisms underlying its growth, we performed a comparative transcriptomic analysis of muscle and liver tissues of fast- and slow-growing L. longirostris. A total of 580 and 511 differentially expressed genes (DEGs) were obtained in the muscle and liver tissues, respectively. We selected 10 DEGs each from muscle and liver tissues by qRT-PCR to verify the reliability of RNA-seq, and it was found that the expression patterns of these genes were consistent with RNA-seq analysis results. According to the differential expression and functional enrichment analysis of genes, we found differences in the expression of several growth-related genes between fast- and slow-growing individuals. These genes may contribute to the differences in the growth of L. longirostris by influencing muscle growth and the metabolism of substances and energy. In particular, the pk and fabp genes were highly expressed in fast-growing individuals, while the cart, leptin, pepck, murf1, trim32, and pparα genes exhibited higher levels in slow-growing individuals. It was speculated that genes related to feeding behavior might be the key genes in regulating the growth of L. longirostris, while glycolytic/gluconeogenic metabolic pathway, lipid metabolism, and ubiquitin-proteasome pathway might be the main pathways involved in regulating body weight of L. longirostris. This study could enrich the available gene resources and provide a valuable basis for further studies on the regulatory mechanisms of growth in L. longirostris.

Myxobolus dumerilii sp. n. (Myxozoa: Myxobolidae) infecting the brain of Chinese longsnout catfish Tachysurus dumerili (Bleeker) in China.

During an investigation of Myxobolus diversity in the Chinese longsnout catfish Tachysurus dumerili (Bleeker), a new species infecting the intracranial epidermis of the host was discovered. Upon opening the cranial cavity, several round whitish plasmodia measuring 0.55-0.80 mm in diameter were observed. Fresh spores (n= 50) were pyriform in the frontal view and fusiform in the sutural view, with a length of 15.4±0.6 (13.9-16.5) μm, width of 9.1±0.4 (8.3-9.8) μm, and thickness of 7.0±0.4 (6.3-7.9) μm. The spores had smooth shell surfaces and transparent membrane sheaths in the posterior. No folds, intercapsular appendix, and caudal appendages were observed. Two equal polar capsules were pyriform and measured 7.5±0.5 (6.7-8.7) μm in length and 3.2±0.3 (2.5-3.6) μm in width. The polar filaments were coiled with five to six turns and perpendicular to the polar capsule length. A BLAST search indicated M. dumerilii sp. n. was closely related to five Myxobolus species (with sequences similarities ranging from 90.54% to 96.52%) found in different organs of yellow catfish Tachysurus fulvidraco (Richardson), rather than the T. dumerili-infecting species M. branchiola Dong and Zhao, 2014 (with 90.5% sequence similarity). Phylogenetic analysis showed that M. dumerilii sp. n. didn't form sister clade with brain-infecting Myxobolus spp, but clustered with M. jianlinensis Gao et Zhao, 2020 and M. voremkhai Akhmerov, 1960 within the Siluriformes-clade with highly supported values, indicating that the host specificity may play a stronger signal than site infections during the evolution of Myxobolus species. Based on the morphological, ecological, and molecular differences observed between the newly discovered species and other available Myxobolus species, M. dumerilii sp. n., is proposed and described in this study.

Single-nuclei RNA-seq reveals skin cell responses to Aeromonas hydrophila infection in Chinese longsnout catfish Leiocassis longirostris.

As the primary natural barrier that protects against adverse environmental conditions, the skin plays a crucial role in the innate immune response of fish, particularly in relation to bacterial infections. However, due to the diverse functionality and intricate anatomical and cellular composition of the skin, deciphering the immune response of the host is a challenging task. In this study, single nuclei RNA-sequencing (snRNA-seq) was performed on skin biopsies obtained from Chinese longsnout catfish (Leiocassis longirostris), comparing Aeromonas hydrophila-infected subjects to healthy control subjects. A total of 19,581 single nuclei cells were sequenced using 10x Genomics (10,400 in the control group and 9,181 in the treated group). Based on expressed unique transcriptional profiles, 33 cell clusters were identified and classified into 12 cell types including keratinocyte (KC), fibroblast (FB), endothelial cells (EC), secretory cells (SC), immune cells, smooth muscle cells (SMC), and other cells such as pericyte (PC), brush cell (BC), red blood cell (RBC), neuroendocrine cell (NDC), neuron cells (NC), and melanocyte (MC). Among these, three clusters of KCs, namely, KC1, KC2, and KC5 exhibited significant expansion after A. hydrophila infection. Analysis of pathway enrichment revealed that KC1 was primarily involved in environmental signal transduction, KC2 was primarily involved in endocrine function, and KC5 was primarily involved in metabolism. Finally, our findings suggest that neutrophils may play a crucial role in combating A. hydrophila infections. In summary, this study not only provides the first detailed comprehensive map of all cell types present in the skin of teleost fish but also sheds light on the immune response mechanism of the skin following A. hydrophila infection in Chinese longsnout catfish.

Identification of a candidate sex-determining gene, ptf1aY, in the Chinese longsnout catfish (Leiocassis longirostris) through high-throughput sequencing

Identifying sex-specific molecular markers and elucidating sex determination mechanisms are critical in sex-controlled breeding in aquaculture. Chinese longsnout catfish (Leiocassis longirostris) is characterized by rapid male growth, suggesting that all-male production will be economically desirable in aquaculture. In this study, novel sex-specific sequences were identified in the Chinese longsnout catfish by using comparative genomics with high-throughput sequencing. Based on the variable regions between the X (1513 bp) and Y (862 bp) sequences, a pair of Y-specific primers was designed to discriminate the genetic sex of Chinese longsnout catfish. The specificity and universality of these primers were verified in two breeding and three wild populations. Sequence analysis revealed that the 1513 and 862 bp were pancreas transcription factor 1a (ptf1a) homologous genes, implying that Chinese longsnout catfish possess an XY sex-determination system, with ptf1a as the sex-linked gene. Two ptf1a cDNA sequences were isolated and named ptf1aX and ptf1aY based on their sites on the X and Y chromosomes. The ptf1aY gene is a truncated copy of ptf1aX on the Y chromosome. The proteins encoded by ptf1aX (263 aa) and ptf1aY (199 aa) showed high sequence identity (65.40 %). Expression analysis showed that ptf1aY mRNA was specifically detected in the testes, and ptf1aX was expressed in the both ovaries and testes. Thus, ptf1aY is a candidate male sex-determining gene in the Chinese longsnout catfish. Our study greatly contributes to understanding sex determination mechanisms and developing all-male population of Chinese longsnout catfish.

Effect of β-cyclodextrin deodorization on the volatile chemicals and functional properties of three types of gelatins.

The exploration of deodorization is important for the application of gelatin in food industry. In this work, the effect of β-cyclodextrin (β-CD) deodorization on the volatile chemicals and functional properties of three types of gelatins (commercial porcine skin gelatin, cold water fish skin gelatin, and Chinese longsnout catfish skin gelatin) were studied. The results suggested the odors of commercial gelatins were significantly less than home-extracted gelatins. The β-CD deodorization efficiency was dependent on both β-CD concentration and volatile chemical. (E)-2-Octenal (C8H14O), 1-octen-3-ol (C8H16O), 2-pentyl-furan (C9H14O), and hentriacontane (C17H36) could be deodorized at low β-CD concentration (even at 2 mg/mL). The best β-CD deodorization concentration for 66.7 mg/mL of Chinese longsnout catfish skin gelatin was 30 mg/mL. β-CD addition could not change the gel forming ability and emulsion activity of gelatins, whereas it had different and concentration-dependent effects on the emulsion stability of gelatins. β-CD addition had no obvious effects on the droplet sizes, droplet coalescence and liquid-gel transition behaviors, but had different effects on the creaming of the emulsions stabilized by three types of gelatins. The encapsulation of β-carotene did not significantly change the droplet trimodal size distribution and liquid-gel transition of fish oil-loaded emulsions. However, β-carotene might delay the droplet coalescence. The creaming stability of β-carotene/fish oil-loaded gelatin/β-CD-stabilized emulsions was dependent on the gelatins, β-CD, and β-carotene. Finally, the β-carotene retention in the emulsions was dependent not on β-CD addition but on the nature of the gelatins. These results provided useful information to understand the molecular deodorization behaviors and explore the deodorization of emulsifiers for food emulsions.

Temporal genetic variation of the Chinese longsnout catfish (Leiocassis longirostris) in the upper Yangtze River with resource decline

Temporal genetic variation of the Chinese longsnout catfish (Leiocassis longirostris) in the upper Yangtze River with resource decline

Genetic Diversity of Chinese Longsnout Catfish (Leiocassis longirostris) in Four Farmed Populations Based on 20 New Microsatellite DNA Markers

Freshwater aquaculture has a long and vibrant tradition in China. The Chinese longsnout catfish (Leiocassis longirostris) is a popular economic freshwater fish native to China. Understanding the genetic structure of L. longirostris populations is important for ensuring the efficacy of management practices and the sustainability of future increases in production. In this study, we used Illumina sequencing technology to isolate 20 novel polymorphic microsatellites from the genome of L. longirostris. These microsatellites were used to analyze the genetic diversity of 240 L. longrostris individuals from four populations. Genetic diversity parameters (NA, HO, HE, I, PIC, and FST) of the four farmed L. longirostris populations were analyzed. The level of genetic differentiation among the four farmed L. longirostris populations (inferred by pairwise comparisons of FST values) was low, but the genetic diversity of these populations was high, indicating that they still provide useful sources of genetic variation that could aid in breeding efforts. The STRUCTURE and ADMIXTURE analyses indicated that admixture might be occurring in the four L. longirostris populations, especially between the MS and YB populations. Understanding the genetic diversity of farmed L. longirostris populations and inbreeding prevention could greatly aid in breeding and production. These newly isolated microsatellite markers and the high genetic diversity of L. longirostris populations in the main breeding areas have important implications for the breeding and stock management of L. longirostris.

Genome-wide association study reveals growth-related markers and candidate genes for selection in Chinese longsnout catfish (Leiocassis longirostris)

Growth-related traits are economically important in fish because they directly affect fish production. The Chinese longsnout catfish (Leiocassis longirostris) is an important aquaculture species and its consumption is growing in China. In this study, using 200 individuals and high-throughput SNP genotyping technology, we performed the first genome-wide association study (GWAS) in L. longirostris to identify putative genomic regions and candidate genes associated with growth traits (including body mass, total length, standard length, head width, snout length, and caudal peduncle depth). The morphometrics of these traits were highly correlated (Pearson's correlation coefficients = 0.88–0.96, p < 0.05). GWAS detected 12, 5, 6, 9, 4, and 8 SNPs loci that were significantly associated (-log10P ≥ 5.21) with body mass, total length, standard length, head width, snout length, and caudal peduncle depth, respectively. Subsequently, within the 100 kb upstream and downstream regions surrounding these significant SNPs, 96, 31, 39, 61, 22, and 36 candidate genes for the 6 growth traits, respectively, were detected. Interestingly, chromosome (Chr) 16 had the most SNPs significantly associated with growth traits, and the majority of those were shared among multiple growth-related traits. In addition, multiple candidate genes surrounding these SNPs have been shown to serve essential functions in biological processes closely-related to growth, such as enox2, ky, and coma1. These results indicated that Chr16 may be central to growth characteristics. Other Chrs had genes involved in bone development, cell proliferation, and fatty acid metabolism, including matn1, sdc3, if2b3, kif3a, h1b, cadh7, rerg, and fabph. Our findings not only help understand the genetic architecture of growth traits in fish, but facilitate the identification of candidate genes for marker-assisted selection towards breeding faster growing L. longirostris in the future.

Identification of male sex-specific markers using genome re-sequencing in the Chinese longsnout catfish Leiocassis longirostris

The Chinese longsnout catfish (Leiocassis longirostris Günther), an indigenous commercially important fish species in China, exhibits markedly sex dimorphism in growth, which the males grow much faster than females. So, we aimed to develop sex-specific DNA markers to accelerate the development of sex control techniques for L. longirostris. In this study, 15 individuals of each sex were sequenced using whole-genome re-sequencing technology. A total of 238.51 Gb clean data was used to detect the sex associated markers and we found that 2472 loci were enriched in the first 18 Mb of Chr 7, the putative sex-determination region for L. longirostris. All candidate markers were male heterozygous, implying that the sex-determination system of the L. longirostris is the XX/XY type. Using the sequence polymorphism of male and female individuals in this region, we designed six pairs of primers to develop sex-specific markers, of which three markers exclusively exhibited male-specific bands. Further validation showed that the accuracy of sex prediction was up to 100% for individuals in the Meishan, Chengdu, Yibin and Shishou regions, suggesting wide applicability among local populations. Importantly, marker 3 was located in the ACAP1 gene, which may be involved in sex determination or differentiation of L. longirostris. This method for developing sex-specific markers is efficient, simple, and provides a useful reference that can be applied to other fish species. The markers developed in this work could be instrumental for sex control breeding to increase the yield in the L. longirostris aquaculture industry.

Molecular characteristics, polymorphism and expression analysis of mhc Ⅱ in yellow catfish(pelteobagrus fulvidraco)responding to Flavobacterium columnare infection

The major histocompatibility complex (MHC) is an important component of the immune system of vertebrates, which plays a vital role in presenting extrinsic antigens. In this study, we cloned and characterized the mhc ⅡA and mhc ⅡB genes of yellow catfish Pelteobagrus fulvidraco. The open reading frames (ORFs) of mhc ⅡA and mhc ⅡB genes were 708 bp and 747bp in length, encoding 235 and 248 amino acids, respectively. The structure of mhc ⅡA and mhc ⅡB includes a signal peptide, an α1/β1 domain, an α2/β2 domain, a transmembrane region and a cytoplasmic region. Homologous identity analysis revealed that both mhc ⅡA and mhc ⅡB shared high protein sequence similarity with that of Chinese longsnout catfish Leiocassis longirostris. mhc ⅡA and mhc ⅡB showed similar expression patterns in different tissues, with the higher expression level in spleen, head kidney and gill and lower expression in liver, stomach, gall bladder and heart. The mRNA expression level of mhc ⅡA and mhc ⅡB in different embryonic development stages also showed the similar trends. The higher expression was detected from fertilized egg to 32 cell stage, low expression from multicellular period to 3 days post hatching (dph), and then the expression increased to a higher level from 4 dph to 14 dph. The mRNA expression levels of mhc ⅡA and mhc ⅡB were significantly up-regulated not only in the body kidney and spleen, but also in the midgut, hindgut, liver and gill after challenge of Flavobacterium columnare. The results suggest that Mhc Ⅱ plays an important role in the anti-infection process of yellow catfish P. fulvidraco.

Isolation of Protease-Producing Bacteria from Shrimp Paste and the Characteristics of Fermenting Catfish Paste

ABSTRACT In this study, six protease-producing halophilic bacterias were isolated from traditional shrimp paste. These strains were used as mixed starter culture to ferment minced catfish muscle. The pH and total volatile base nitrogen in the group with mixed starter cultures (ZB) was lower than that of the group without starter (ZA). The total acidity and the content of amino acid nitrogen and free amino acid in ZB was higher. Additionally, the ZB exhibited a strong umami and fermented flavor. The results show that protease-producing bacteria could improve the flavor and nutritive value of fermented Chinese long-snout catfish by-products.

Sex-specific markers developed by genome-wide 2b-RAD sequencing confirm an XX/XY sex determination system in Chinese longsnout catfish (Leiocassis longirostris)

Longsnout catfish (Leiocassis longirostris), an important commercial fish in China, shows significant sexual size dimorphism. However, the sex determination system and mechanism of longsnout catfish remain unknown. In this study, an effective protocol of artificial gynogenesis using heterologous sperm was successfully developed and male heterogametic XX/XY sex determination system was revealed in longsnout catfish. Subsequently, sex-specific markers were developed based on isolated homologous X-specific and Y-specific sequences by 2b-RAD sequencing and PCR amplification. Finally, the Y-specific and XY-shared primers were developed and validated in a full-sib family, a gynogenetic population and two local populations, which further verify the sex determination system. Therefore, this study not only reveals XX/XY sex determination system in longsnout catfish, but also provides applicable sex-specific markers for production of all-male population for aquaculture in the future.

Structural and emulsion stabilization comparison of four gelatins from two freshwater and two marine fish skins

This study analyzed the structural and emulsion stabilization properties of two freshwater and two marine fish skin gelatins: Chinese longsnout catfish skin gelatin (CLCSG), silver carp skin gelatin (SCSG), salmon skin gelatin (SSG), and Alaska pollack skin gelatin (APSG). Their gel strengths (Bloom values) were: 361 ± 1 (SCSG) > 253 ± 4 (CLCSG) > 69 ± 1 (SSG) > 36 ± 2 (APSG). Higher molecular weights and α/β subunit contents of gelatins might induce higher gel strengths. Both creaming and droplet stability were completely the same to the contents of imino acids, β-sheet percentages, and β-turn percentages, whereas they were completely the opposite to random coil percentages. The emulsion stabilization mechanisms involved an “fish skin source – protein chemical composition – protein secondary structure – protein functional properties – emulsion stability” route. This study provided useful knowledges for gelatin science and for the comprehensive utilization of aquatic by-products in gelatin industry.

Responses of glycolysis, glycogen accumulation and glucose-induced lipogenesis in grass carp and Chinese longsnout catfish fed high-carbohydrate diet

This study investigated the different adaptive metabolic strategies of grass carp (Ctenopharyngodon idellus) and Chinese longsnout catfish (Leiocassis longirostris Günther) to a high-carbohydrate diet (HCD). Two dietary carbohydrate levels were formulated for grass carp (normal-carbohydrate diet [NCD]: 30%; HCD: 50%) and Chinese longsnout catfish (NCD: 8%; HCD: 20%). Based on transcriptome data, the top twenty KEGG pathway enrichment analyses indicated that five pathways related to carbohydrate metabolism were enriched in grass carp that were fed an HCD, but were not in Chinese longsnout catfish. After 56 d, compared to the fish in the NCD group, grass carp fed an HCD exhibited significant increase in their whole-body lipid content and glucose-induced lipogenesis, including fatty acid synthase content and transcriptional levels of acetyl-CoA carboxylase, sterol regulatory element-binding protein-1, and carbohydrate response element-binding protein. Raised hepatic glycogen content was observed in both grass carp and Chinese longsnout catfish that were fed an HCD. The enhanced glycogen synthesis, including induced glycogen synthase activity and upregulation of mRNA levels of glycogen synthase and serine/threonine-protein phosphatase PP1-beta catalytic subunit, led to accumulation of glycogen in grass carp. However, reduced glycogenolysis with downregulation of the transcriptional levels of phosphorylase kinase regulatory subunit alpha and glycogen phosphorylase caused accumulation of glycogen in Chinese longsnout catfish. In addition, significantly increased intestinal amylase activity and induced glycolysis of glucokinase and pyruvate kinase were observed in grass carp that were fed an HCD. The results indicated that grass carp responded effectively to an HCD by induction of glycolysis, glycogen accumulation and glucose-induced lipogenesis, while Chinese longsnout catfish did not.

Characterization of 55 SNP markers in Chinese longsnout catfish Leriocassis Longirostris

The Chinese longsnout catfish (Leiocassis longirostris) is a commercially important aquaculture species in China. The germplasm resources of L. longirostris have been seriously degraded by human activities, therefore, it is very urgent to develop genetic markers of L. longirostris to investigate the natural resources. Here, a total of 55 single nucleotide polymorphism (SNP) loci were identified using Sequenom MassARRAY based on the L. longirostris transcriptome. Genetic parameters of the loci showed that the minor allele frequency varied from 0.0417 to 0.5000, and that the observed and expected heterozygosity ranged from 0.0833 to 0.8750 and 0.0802 to 0.5021, respectively. 27 loci were identified deviating significantly from the Hardy–Weinberg equilibrium (P < 0.05), and no linkage disequilibrium was found between pairs of loci. These SNP markers will be useful for future population conservation and construction of genetic linkage maps related to L. longirostris.

The characteristics of glucose homoeostasis in grass carp and Chinese longsnout catfish after oral starch administration: a comparative study between herbivorous and carnivorous species of fish.

An oral starch administration trial was used to evaluate glucose homoeostasis in grass carp (Ctenopharyngodon idella) and Chinese longsnout catfish (Leiocassis longirostris Günther). Fish were administered with 3 g of a water and starch mixture (with 3:2 ratio) per 100 g body weight after fasting for 48 h. Fish were sampled at 0, 1, 3, 6, 12, 24 and 48 h after oral starch administration. In grass carp, plasma levels of glucose peaked at 3 h but returned to baseline at 6 h. However, in Chinese longsnout catfish, plasma glucose levels peaked at 6 h and returned to baseline at 48 h. The activity of intestinal amylase was increased in grass carp at 1 and 3 h, but no significant change in Chinese longsnout catfish was observed. The activity of hepatic glucose-6-phosphatase fell significantly in grass carp but change was not evident in Chinese longsnout catfish. The expression levels and enzymic activity of hepatic pyruvate kinase increased in grass carp, but no significant changes were observed in the Chinese longsnout catfish. Glycogen synthase (gys) and glycogen phosphorylase (gp) were induced in grass carp. However, there was no significant change in gys and a clear down-regulation of gp in Chinese longsnout catfish. In brief, compared with Chinese longsnout catfish, grass carp exhibited a rapid increase and faster clearance rate of plasma glucose. This effect was closely related to significantly enhanced levels of digestion, glycolysis, glycogen metabolism and glucose-induced lipogenesis in grass carp, as well as the inhibition of gluconeogenesis.