Search Results (11)

This study investigated the effects of dietary carbohydrate levels on growth performance, body composition, and hepatic expression of metabolic genes in Chinese hook snout carp (Opsariichthys bidens). Fish were fed five isonitrogenous diets with graded α-starch levels (8%, 14%, 20%, 26%, and 32%) for 56 days. The diet containing 14% α-starch significantly increased the weight gain rate (WGR) and specific growth rate (SGR) of O. bidens (p < 0.05). Both broken-line and polynomial regression analyses on WGR and SGR consistently indicated an optimal dietary α-starch level of approximately 14–17%. High carbohydrate diets significantly elevated plasma glucose, triglyceride, and cholesterol levels, as well as hepatosomatic and intraperitoneal fat indices. Gene expression analysis revealed that moderate carbohydrate intake upregulated lipoprotein lipase (lpl), hormone-sensitive lipase (hsl), and carnitine palmitoyltransferase 1 (cpt1) gene expressions, enhancing lipolysis and β-oxidation, whereas excessive carbohydrate intake (>26% α-starch) suppressed these pathways but strongly induced acc1 gene expressions, promoting lipogenesis. Additionally, glycogen metabolism genes (glycogen synthase (gys) and glycogen phosphorylase (pyg) and glycolysis-related phosphofructokinase (pfk) were responsive to carbohydrate supply, while oxidative metabolism gene cs was downregulated under excessive carbohydrate, implying reduced mitochondrial oxidative metabolism. Overall, O. bidens exhibited limited carbohydrate utilization, with optimal intake supporting growth and metabolic balance, whereas excessive intake redirected glucose toward glycogen and lipid accumulation, leading to metabolic imbalance. Full article

Microplastics threaten freshwater fish health, with probiotics potentially alleviating this stress. This study subjected Opsariichthys bidens fry to 10 μg/L polystyrene microplastics (diameter 100 μm) for seven days, then established control (CK, 0 CFU/g), low (LC, 1 × 10⁷ CFU/g), medium (MC, 1 × 10⁸ CFU/g), and high (HC, 1 × 10⁹ CFU/g) Bacillus coagulans supplementation groups for a 56−day rearing experiment. Results indicated that microplastic stress significantly reduced intestinal digestive enzyme activity in O. bidens and induced oxidative stress. Following stress removal, probiotic-treated groups exhibited markedly superior growth performance compared to the control (CK). Notably, the high-concentration probiotic group (HC) demonstrated intestinal trypsin levels approaching pre-stress levels, with no significant differences in liver antioxidant capacity (T−AOC, CAT, SOD) compared to pre-stress levels (p > 0.05). Furthermore, compared to the control group (CK), probiotic-treated fish exhibited upregulated growth- and immune-related genes (igf, ghr, tnf−α, il−1β), alongside optimized gut microbiota composition, characterized by increased abundance of Bacillus and decreased abundance of Pseudomonas and Aeromonas. This study demonstrates that B. coagulans alleviates microplastic-induced stress in O. bidens, offering insights for aquatic ecosystem conservation and biological remediation of microplastic pollution. Full article

Stream-dwelling fishes face diverse hydrological pressures, making the broadly distributed Opsariichthys bidens an ideal model for analyzing adaptive evolution. To elucidate its adaptation to a high-dissolved-oxygen and high-flow-velocity stream environment, a high-quality genome with comprehensive annotation is essential. In this study, we present the first telomere-to-telomere (T2T) reference genome for O. bidens, constructed using PacBio HiFi, Oxford Nanopore Ultra-long, and Hi-C technologies. The assembled genome spans 841.96 Mb, comprising 38 chromosomes, each in a single contig (contig N50 = 22.42 Mb, 2.5-fold higher than the previous version), achieving a gap-free standard with 99.34% BUSCO completeness. Additionally, 38 centromeric sequences, 37 double-telomeric sequences, and 1 single-telomeric sequence were successfully identified, providing essential molecular markers. Phylogenetic analysis revealed a divergence time of 13.5 million years between O. bidens and its closely related species Z. platypus, with collinearity analysis confirming their high genomic conservation. Gene family analysis revealed 350 expanded families enriched in pathways associated with adaptation to high-dissolved-oxygen environments (e.g., antioxidant defense, oxidative phosphorylation, mitochondrial electron transport chain) and high-flow-velocity environments (e.g., exercise endurance, myocardial contraction, actin binding). Positive selection analysis further identified multiple pathways and key genes involved in mitochondrial optimization, oxygen utilization, and metabolic regulation. The T2T assembly greatly improves assembly continuity and enabling precise identification of centromeres and telomeres for O. bidens. These results provide a robust foundation for studying its adaptive evolution to stream environment. Full article

Sex-specific markers are important basic tools for the sex-controlled breeding of farmed fish. Here, we aimed to develop a rapid yet accurate, cost-effective method for determining the genetic sex of the Chinese hooksnout carp (Opsariichthys bidens), a freshwater fish. Using whole-genome resequencing technology, along with bulked segregant analysis (BSA) and chromosome quotient (CQ) methods, sex-specific regions were screened, and corresponding primers were designed to validate the screening results. A total of 45 sex-specific regions were successfully screened through BSA sequencing and CQ analysis, and 50 pairs of primers were designed for use in the screening verification. The Mar28 primer pair showed stable sex specificity in multiple populations of O. bidens, accurately distinguishing male from female individuals. This primer pair amplified two bands (509 and 814 bp) in males, but only one band (509 bp) in females. The genetic sex identification method established here provides a theoretical basis for studying the mechanism of sex determination in O. bidens, has implications for the monosex culture and molecular breeding of O. bidens, and has significant scientific and practical value. Full article

To investigate the effects of environmental enrichment on the growth and welfare level of the Chinese hooksnout carp (Opsariichthys bidens), an experiment was carried out for 56 d with four types of enrichment environments: low-density physical enrichment, high-density physical enrichment, low-density social enrichment, and high-density social enrichment. The experimental results revealed that both physical and social enrichment treatments positively affected the growth and gonadal development of O. bidens. The physical enrichment treatment was found to increase the antioxidants’ content, such as CAT, SOD, and GSH, in the liver of O. bidens. Moreover, this treatment was able to lead to a reduction in MDA content and enhancement of the fish’s antioxidant capabilities. Behavioral observations, cortisol level analysis, and pcna gene expression analysis indicated that the physical enrichment treatment redused the clustering, aggression, and stress behaviors of O. bidens, maintaining them in a low-stress state. In most respects, the high-density physical enrichment has more positive effects than the low-density one. In contrast, the social enrichment treatments resulted in higher stress levels for O. bidens. Full article

To investigate difference in the quality of the different parts (back, tail muscles, and fish skin) of Opsariichthys bidens from pond and rice field cultures, a comparative study was conducted in terms of nutritional composition, volatile flavor profiles and gut microbiota. In detail, the texture, free amino acids, fatty acids were further assessed. The results suggested that the moisture content, crude protein and crude fat content in the skin of O. bidens are higher than those in the back and tail muscles, regardless of breeding modes. The fish cultured in the rice field had a higher protein content than those from the pond culture, while the fat content of the rice field-cultured fish was significantly low compared to the fish from the pond culture, especially in the back and tail parts. A total of 43 volatile components were detected by Gas Chromatography–Mass Spectrometry (GC-MS), with a maximum of 18 types of aldehydes and the highest concentration being nonanal. Compared to pond cultures, the fish from the rice field cultures showed more abundant flavor composition and odor-active compounds. The total content of DHA (Docosahexaenoic Acid) and EPA (Eicosapentaenoic Acid) in the rice field-cultured fish was higher than that of the pond group, while no significant disparity in amino acid composition was observed (p > 0.05). Comparative and clustering analyses of gut microbiota revealed notable discrepancies in the gut microbiota of O. bidens from two aquaculture systems. However, an inherent correlation between the gut microbiome and meat quality would be further emphasized in further studies. This study can offer a theoretical reference for the development of high-quality aquatic products by selecting the appropriate aquaculture models. Full article

Opsariichthys bidens (O. bidens) is a fish species native to China and sensitive to temperature changes. In this study, the effects of acute temperature stress on brain gene expression in O. bidens were investigated by sampling brain tissues from specimens exposed to three different temperatures (15 °C, 25 °C, and 35 °C) for varying durations of 2 h, 4 h, 6 h, and 8 h. The study focused on analyzing the expression patterns of key genes implicated in neural function and stress response, including brain-derived neurotrophic factor (BDNF), c-FOS, heat shock proteins (HSP70, HSP90), endoplasmic reticulum stress markers (IRE1, GRP78), oxidative stress enzymes (CAT, SOD), and apoptotic regulators (caspase3, Bax). The findings revealed that upon exposure to acute heat stress, the expression levels of the aforementioned genes in the brain of O. bidens were up-regulated within 2 h, peaking at the 4-h mark. Conversely, following acute cold stress, the expression of c-FOS, BDNF, HSP70, HSP90, SOD, and CAT genes increased significantly after 4 h, while caspase3 expression was notably elevated at the 6-h mark, with no significant impact observed on Bax, IRE1, or GRP78 gene expression levels. The study suggested that the brain of O. bidens responds to high temperatures through mechanisms involving neural activation, heat shock proteins, endoplasmic reticulum stress, oxidative stress, and apoptosis. Similarly, adaptation to low temperatures by O. bidens’ brain was associated with neural activation, regulation of heat shock proteins, oxidative stress responses, and apoptotic processes. Overall, this research aimed to elucidate the impact of temperature stress on brain physiology and the adaptive mechanisms of O. bidens at the genetic level, providing a foundational understanding of its temperature adaptation strategies. Full article

In recent years, the Chinese hook snout carp (Opsariichthys bidens) is becoming increasingly popular due to its high nutritional value and delicious taste. However, anthropogenic influences have caused a rapid reduction in its population. Considering long-term development sustainability, it is essential to conduct research on its reproductive development. In this study, the germ-cell related genes dazl (Obdazl) and dnd (Obdnd) were cloned, and their expression patterns were revealed. RT-PCR analysis indicated that Obdazl and Obdnd were specifically expressed in gonads. In the testis, Obdazl and Obdnd RNAs have a similar expression pattern: their transcripts were abundant in spermatogonia, gradually decreased, and eventually disappeared during spermatogenesis. Early oocytes in the ovary exhibited strong expression of Obdazl and Obdnd RNAs and reduced remarkably after peak expression at III oocytes. Surprisingly, Obdazl RNA was dynamically found in perinuclear spots that finally aggregated into the Balbiani body (Bb) in the early oocytes. Moreover, Obdazl 3′ UTR enabled the reporter gene to be expressed stably in medaka PGCs, suggesting that dazl was identified as the germ cell marker in O. bidens, which may provide perspectives for further studies on the development of PGCs in the future. Full article

The hook snout carp Opsariichthys bidens is an important farmed fish in East Asia that shows sexual dimorphism in growth, with males growing faster and larger than females. To understand these complex traits and improve molecular breeding, chromosome-level genome assembly of male O. bidens was performed using Illumina, Nanopore, and Hi-C sequencing. The 992.9 Mb genome sequences with a contig N50 of 5.2 Mb were anchored to 38 chromosomes corresponding to male karyotypes. Of 30,922 functionally annotated genes, 97.5% of BUSCO genes were completely detected. Genome evolution analysis showed that the expanded and contracted gene families in the male O. bidens genome were enriched in 76 KEGG pathways, and 78 expanded genes were involved in the GnRH signaling pathway that regulates the synthesis and secretion of luteinizing hormone and glycoprotein hormones, further acting on male growth by inducing growth hormone. Compared to the released female O. bidens genome, the number of annotated genes in males was much higher (23,992). The male chromosome LG06 exhibited over 97% identity with the female GH14/GH38. Male-specific genes were identified for LG06, where structural variation, including deletions and insertions, occurred at a lower rate, suggesting a centric fusion of acrocentric chromosomes GH14 and GH38. The genome-synteny analysis uncovered significant inter-chromosome conservation between male O. bidens and grass carp, the former originating from ancestral chromosome breakage to increase the chromosome number. Our results provide a valuable genetic resource for studying the regulation of sexual dimorphism, sex-determining mechanisms, and molecular-guided breeding of O. bidens. Full article

Opsariichthys bidens belongs to the family Cyprinidae and is a small freshwater economic fish widely distributed in China. In recent years, the natural resources of O. bidens have been drastically reduced due to overfishing and the destruction of the water environment. The in vitro culture and long-term preservation of germ stem cells are the key technologies to keep genetic resources from degeneration. However, except for the establishment of the first long-term cultured medaka spermatogonia cell line (SSC) capable of producing sperm in vitro in 2004, no other long-term cultured SSC line has been found in other fish species. In this study, we successfully established another long-term-cultured spermatogonial stem cell line from Opsariichthys bidens (ObSSC). After more than 2 years of culture, ObSSC had a diploid karyotype and stable growth, with the typical gene expression patterns of SSC. Under in vitro culture, ObSSC could be induced to differentiate into sperm and other different types of somatic cells. In vivo, ObSSC could differentiate into different cells of three germ layers upon being transplanted into zebrafish embryos. Our research helps to explore the potential and regulation mechanism of fish SSC differentiation and spermatogenesis in vitro, provides a new way for solving the problem of fish genetic resource degradation and lays a foundation for further research on fish germ cell transplantation. Full article

Spermatogenesis is the intricate and coordinated process by which spermatogonia develop into haploid differentiated spermatozoa. Mitochondria are essential for spermatogenesis, and prohibitin (PHB) is closely associated with mitochondrial structure and function during spermatogenesis. Although PHB has been implicated in spermatogenesis in some taxa, its roles in Opsariichthys bidens have not been determined. In this study, the expression patterns and potential functions of PHB in spermatogenesis in O. bidens were characterized using histological microscopic observations, PCR cloning, real-time quantitative PCR (qPCR), Western blotting (WB) and immunofluorescence (IF). The full-length cDNA of Ob-phb was 1500 bp encoding 271 amino acids. A sequence alignment demonstrated that the PHB protein is conserved among different animals. qPCR revealed that phb mRNA is widely distributed in O. bidens and highly expressed in the testes at stages IV and V. WB revealed that Ob-PHB is located in the mitochondria of testes. IF revealed the colocalization of PHB signals and mitochondria. Signals were detected around nuclei in spermatogonia and spermatocytes, gradually moving to the tail region during spermiogenesis, and finally aggregating in the midpiece. These results indicate that Ob-PHB was expressed in the mitochondria during spermatogenesis. In addition, this study proposed Ob-PHB may participate in the degradation of mitochondria and cell differentiation during spermatogenesis. Full article