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Clock genes play a pivotal role in the rhythm maturation of bony fish ovaries. To explore the role of clock genes in the rhythmic ovarian development and maturation of tongue sole (Cynoglossus semilaevis), we used real-time fluorescent quantitative PCR technique to analyze the expression profiles of circadian locomotor output cycles Kaput 1a (Clock1a), brain and muscle Arntlike 1a (Bmal1a), Cryptochrome 1a (Cry1a), Cryptochrome 2 (Cry2), and Period 2 (Per2) at the ovarian stages Ⅱ, Ⅲ, Ⅳ, Ⅴ, and Ⅵ.The coding DNA sequence (CDS) of five clock genes were cloned and phylogenetically analyzed. We found that the CDS sequence length of Clock1a was 1 620 bp and encoded 539 amino acids, with the encoded amino acid sequence of Clock1a having a predicted molecular weight of 81.9 kDa. Clock1a has the functional domain PASD1 (consisting of 64 amino acids) and PAS11 (consisting of 103 amino acids). The CDS sequence length of Bmal1a was 1 881 bp and encoded 626 amino acids, with the encoded amino acid sequence of Bmal1a having a predicted molecular weight of 68.9 kDa. In the Bmal1a sequence, the functional domain PASD3 is composed of 63 amino acids, and the functional domain PAS11 is composed of 103 amino acids. The CDS sequence length of Cry1a was 1 896 bp and encoded 631 amino acids, with the encoded amino acid sequence of Cry1a having a predicted molecular weight of 71.4 kDa. Its functional domain FAD7 was composed of 199 amino acids. The CDS sequence length of Cry2 was 2 007 bp and encoded 669 amino acids, with the encoded amino acid sequence of Cry2 having a predicted molecular weight of 76.0 kDa. The Cry2 sequence contains a functional domain FAD7 consisting of 199 amino acids. The CDS sequence length of Per2 was 4 248 bp, encoding 1 415 amino acids, and the encoded amino acid sequence of Per2 has a predicted molecular weight of 154.0 kDa. In the Per2 sequence, the functional domain PeriodC consists of 295 amino acids and a functional domain PAS11 consists of 102 amino acids.The neighbor-joining method was used to analyze the Clock1a, Bmal1a, Cry1a, Cry2, and Per2 phylogenetic relationships between C. semilaevis and other bony fish, amphibians, birds, and mammals. The homology of Clock1a, Bmal1a, Cry1a, Cry2, and Per2 with other bony fish was 60%–79%, 94%–100%, 85%–91%, 84%–94%, and 70%–84%, respectively. Therefore, we believe that these five amino acid sequences show strong conserved property. In addition, the homology of Cry1a and Cry2 was 62%, indicating that Cry1a and Cry2 evolved differently during the evolution of C. semilaevis. In the constructed phylogenetic tree, Clock1a, Bmal1a, Cry1a, Cry2, and Per2 of C. semilaevis were clustered together with other bony fishes, indicating a close relationship between C. semilaevis and other bony fish in the evolutionary process. Moreover, the homology of Clock1a between C. semilaevis and mammals, birds, and amphibians is low, indicating that there are evolutionary differences in the evolutionary process of Clock1a. The high homology of Bmal1a, Cry1a, Cry2, and Per2 with mammals, birds, and amphibians suggests that these four clock genes were strongly conserved during the evolution of C. semilaevis.In the present study, we found that the expression levels of five clock genes were high in stagesⅡ and Ⅲ, which were equivalent to the non-reproductive season (P < 0.05). However, the expression levels of five clock genes were low in stages Ⅳ and Ⅴ, which were equivalent to the reproductive season (P < 0.05). Therefore, the expression profiles of Clock1a, Bmal1a, Cry1a, Cry2, and Per2 in the ovaries of C. semilaevis also have seasonal characteristics. The ovarian development and maturation of C. semilaevis goes through stages Ⅱ, Ⅲ, Ⅳ, Ⅴ, and Ⅵ, and then reaches stage Ⅱ again and starts a new reproductive cycle. The variation patterns of seasonal factors, such as light and temperature, in fish ovaries were consistent with the annual expression patterns of the five clock genes in this study. Therefore, it can be considered that the expression of clock genes in C. semilaevis has an annual cycle. The findings presented in this study can enrich the theory of ovarian development and maturation of C. semilaevis and provide a theoretical basis for improving breeding technology and seedling efficiency.

The whitespotted conger (Conger myriaster) is an important fish species with high economic value in China and Japan owing to its high nutritional content. It occupies an important position in marine-eel export in China. C. myriaster has the potential to be artificially cultured and has promising economic prospects. Thus, there is growing international interest in C. myriaster research. Indeed, to meet the demands of domestic and foreign markets, artificial culturing of C. myriaster is urgently required. However, at present, there is no report on the research of C. myriaster reared in industrial recirculating aquaculture systems. Feeding frequency has been reported to affect feed intake and growth performance in a number of fish species. Feed management in terms of optimization of feeding frequency has emerged as one of the crucial areas of research in the field of aquaculture. Overfeeding and leftover food disrupts the water quality, while inadequate food supply has direct impact on production cost. Traditional flow through systems uses large volumes of water, and intensified aquaculture has drawbacks, such as large amount of discharged waste from effluent water. Among the excreted nutrients, nitrogen and phosphorus constitute the largest proportion. Sustainability with low environmental impacts is one of the concerns when developing aquaculture systems. Based on the concepts of reduced water consumption and efficient water management, recirculating aquaculture systems offer the possibility of creating a sustainable future for fish production. Thus, a 70-day experiment was conducted to investigate the effects of different feeding frequencies and water quality on the growth performance and physiological and biochemical indices of C. myriaster [body weight: (150.64±5.43) g] reared in industrial recirculating aquaculture systems; physiological and ecological methods were used in this study. The experiment comprised two feeding frequency groups, feeding once (group T1) and twice (group T2) per day, and each treatment group had three replicates. The average body weight of the fish in each culture pond and the water quality indices of the culture system were measured and analyzed every 14 d. At the end of the experiment, the blood, liver, and intestine samples of C. myriaster were collected to determine and analyze growth and physiological indices. The results indicated that (1) the growth performance of group T2 was better than that of group T1. The final body weight, final body length, weight gain, and specific growth rate of group T2 was significantly higher than those of group T1 (P < 0.05). The feed coefficient of group T1 was significantly higher than that of group T2 (P < 0.05). However, no significant differences were found in the final body height, liver body ratio, visceral body ratio, condition factor, or survival rate at different feeding frequencies (P > 0.05). (2) The serum malondialdehyde of group T1 was significantly higher than that of group T2 (P < 0.05). The hepatic alanine aminotransferase and hepatic aspartate transaminase of group T1 was significantly higher than those of group T2 (P < 0.05). The intestinal trypsin of group T2 was significantly higher than that of group T1 (P < 0.05). There were no significant differences in the levels of serum superoxide dismutase, serum catalase, intestinal amylase, or intestinal lipase between groups T1 and T2 (P > 0.05). (3) In the 24 h changes of ammonia nitrogen (NH4+-N) and nitrite nitrogen (NO2–-N), the change patterns of the two indices in outlet of the T1 group were similar to those of the outlet of the bio-filter; the two indices of the outlet water in T1 and T2 groups were one (24:00) and two peaks (20:00 and 08:00) respectively; the difference in NH4+-N in the outlet water of the two test groups within 24 h was significant (P < 0.05); at 04:00 and 08:00, the NO2–-N content of the outlet water of the biofilter was significantly lower than that of the other two test groups (P < 0.05); the 24 h changes range of NH4+-N and NO2–-N in T2 group were smaller than those in T1 group. (4) During the whole test period, each water quality index was maintained within the safe breeding range, and no significant differences were found in NH4+-N, NO2–-N, chemical oxygen demand, and active phosphate concentration between T1 and T2 groups (P > 0.05); at the end of the test, the total nitrogen and total phosphorus of T2 group were significantly higher than those of T1 group (P < 0.05); the biofilter has different treatment effects on various water quality indices, among which the treatment effect on NH4+-N is the most efficient, up to 54.23%. Based on the above results, the feeding frequency of twice per day was better than that of once per day in the industrial recirculating aquaculture mode for C. myriaster (body weight: 150~250 g). Without affecting the survival rate and condition factor, the twice per day group can save costs and improve economic benefits. However, due to the limitations of the test conditions, we did not explore more times of feeding, and further tests are needed in the future. The predominance, which was the high efficiency of water qualities treatment and optimal effect of culture, was demonstrated obviously in closed recirculating aquaculture systems. This study aims to provide a theoretical reference for the appropriate feeding strategy in the industrial recirculating aquaculture model of C. myriaster.

In this study, the influence of fasting on hepatic glucose and lipid metabolism was explored by examining biochemical, antioxidative, and morphological indicators and transcriptional expression in the liver of javelin goby (Synechogobius hasta) after 0, 3, 7, or 14 days of starvation. Marked reductions in hepatic glycogen and triglycerides occurred from the seventh day of starvation until the end of the trial (p < 0.05). However, no alterations in hepatic cholesterol or protein were detected throughout the entire experiment (p > 0.05). During fasting, the activities of pyruvate kinase, lactate dehydrogenase, and glycogen phosphorylase a all rose firstly and then fell (p < 0.05). The activities of hepatic fatty acid synthase and acetyl-CoA carboxylase were minimized to their lowest levels at the end of food deprivation (p < 0.05), while lipase was elevated after 7–14 days of fasting (p < 0.05). Catalase, glutathione, and the total antioxidative capacity were increased and maintained their higher values in the later stage of fasting (p < 0.05), whereas malondialdehyde was not significantly changed (p > 0.05). Hepatic vein congestion, remarkable cytoplasmic vacuoles, and irregular cell shape were present in S. hasta which endured 3–7 days of fasting and were less pronounced when food shortage was prolonged. In terms of genes associated with glucose and lipid metabolism, the hepatic phosphofructokinase gene was constantly up-regulated during fasting (p < 0.05). However, the mRNA levels of glycogen synthase and glucose-6-phosphatase were obviously lower when the food scarcity extended to 7 days or more (p < 0.05). Fatty acid synthase, stearoyl-CoA desaturase 1, and peroxisome proliferator-activated receptor γ were substantially down-regulated in S. hasta livers after 7–14 days of food deprivation (p < 0.05). However, genes involved in lipolysis and fatty acid transport were transcriptionally enhanced to varying extents and peaked at the end of fasting (p < 0.05). Overall, starvation lasting 7 days or more could concurrently mobilize hepatic carbohydrates and fat as energy resources and diminished their hepatic accumulation by suppressing biosynthesis and enhancing catabolism and transport, ultimately metabolically and structurally perturbing the liver in S. hasta. This work presents preliminary data on the dynamic characteristics of hepatic glucose and lipid metabolism in S. hasta in response to starvation, which may shed light on the sophisticated mechanisms of energetic homeostasis in fish facing nutrient unavailability and may benefit the utilization/conservation of S. hasta.

Soybean oil (SO), an important plant-derived lipid, is routinely used in aquafeed as a partial substitute for fish oil. However, the effect of various contents of SO in a SO-based aquafeed on specific aquatic animals and the underlying mechanisms are unclear. In this study, five isonitrogenous diets containing different SO contents (0 %, 3 %, 6 %, 9 %, and 12 %, named as S0, S3, S6, S9, and S12, respectively) were prepared with SO as the predominant lipid source, and 12-week feeding experiments were conducted on juvenile grass carp (Ctenopharyngodon idella) (initial weight: 12.54 ± 0.08 g). Apart from lower feed conversion ratio in the S6 and S9 groups (P 0.05). The S12 group exhibited significant decrease in the final weight and weight gain rate and increase in the viscerosomatic index (P

This study aimed to explore the effects of different starch source diets on the growth performance and hepatopancreas RNA-seq of grass carp. Juvenile grass carp (initial body weight of 39.4 ± 1.6 g) were fed diets containing 25% corn (CO), potato (PO), and wheat (WH) starch for 8 weeks, respectively. The weight gain ratio (WGR) was significantly lower, whereas the visceral somatic index (VSI) and feed conversion ratio (FCR) were significantly higher in the CO group than those in the PO and WH groups. These indicators did not significantly differ between the PO and WH groups. Hepatopancreas RNA-seq analysis showed that 536, 514, and 647 differentially expressed genes (DEGs) were screened out in the comparisons of PO vs. WH, PO vs. CO, and CO vs. WH. The DEGs were mainly enriched in the several known pathways involved in steroid biosynthesis, cell cycle, fatty acid metabolism, and fat digestion and absorption according to Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis. The major DEGs related to lipid and carbohydrate metabolism were analyzed, in which lipogenesis-related DEGs (fasn, acc1, scd1, elovl6, and me1), fat digestion and absorption-related DEGs (fabp7, apoa1, apoa4, and pla2), and glycometabolism-related DEGs (gk, g6pd, and pepck) were down-regulated in the PO group compared with those in the CO and WH groups. Conversely, steroid synthesis-related DEGs (hmgcs, fdft1, sqle, lss, cyp51, msmo1, nsdhl, ugt, cyp1b1, and cyp7a1) were up-regulated in the PO group. These results indicate that the long-term PO ingestion could modulate hepatic lipid metabolism by reducing fatty acid biosynthesis and increasing bile acid biosynthesis. PO may be healthier in contrast to CO alone, which may not be suitable as a starch source in grass carp diet.

Aeromonas hydrophila is a kind of zoonotic pathogen, which can cause bacterial septicemia in fish and bring huge economic losses to global aquaculture. Outer membrane proteins (Omps) are conserved antigens of Aeromonas hydrophila, which can be developed as subunit vaccines. To evaluate the protective efficacy of inactivated vaccine and recombinant outer membrane protein A (OmpA) subunit vaccine against A. hydrophila in juvenile Megalobrama amblycephala, the present study investigated the immunogenicity and protective effects of both vaccines, as well as the non-specific and specific immune response of M. amblycephala. Compared with the non-vaccinated group, both inactivated and OmpA subunit vaccines improved the survival rate of M. amblycephala upon infection. The protective effects of OmpA vaccine groups were better than that of the inactivated vaccine groups, which should be attributed to the reduced bacterial load and enhanced host immunity in the vaccinated fish. ELISA assay showed that the titer of serum immunoglobulin M (IgM) specific to A. hydrophila up-regulated significantly in the OmpA subunit vaccine groups at 14 d post infection (dpi), which should contribute to better immune protective effects. In addition, vaccination enhanced host bactericidal abilities might also attribute to the regulation of the activities of hepatic and serum antimicrobial enzymes. Moreover, the expression of immune-related genes (SAA, iNOS, IL-1 β, IL-6, IL-10, TNF α, C3, MHC I, MHC II, CD4, CD8, TCR α, IgM, IgD and IgZ) increased in all groups post infection, which was more significant in the vaccinated groups. Furthermore, the number of immunopositive cells exhibiting different epitopes (CD8, IgM, IgD and IgZ) that were detected by immunohistochemical assay had increased in the vaccinated groups post infection. These results show that vaccination effectively stimulated host immune response (especially OmpA vaccine groups). In conclusion, these results indicated that both the inactivated vaccine and OmpA subunit vaccine could protect juvenile M. amblycephala against A. hydrophila infection, of which OmpA subunit vaccine provided more effective immune protection and can be used as an ideal candidate for the A. hydrophila vaccine.

Fucoidan and laminarin are polymolecular compounds that extracted from seaweed. As functional polysaccharides, they possess various biological functions such as immunomodulatory, anti-inflammatory, antiviral and antioxidant bioactivities. Fucoidan and laminarin modulate host immune responses by activating immune cells (macrophages, neutrophils, T lymphocytes) and inducing the expression of cytokines (TNFα, IL-1β, IL-6, IL-8, NF-κB). Intelectin is a novel lectin that plays important roles in bacterial agglutination and bactericidal effects by recognizing the polysaccharide components on the cell surface of pathogens, which can also enhance the phagocytosis of macrophages. The present study intends to explore the immunomodulatory effects of fucoidan, laminarin and intelectin on the macrophages of Megalobrama amblycephala. The results showed that the incubation of both fucoidan and laminarin at the concentration of 100 μg/mL for 4 h could enhance the phagocytic capacity of M. amblycephala macrophages, which also showed remodeled cytoskeleton with extended pseudopodia. In addition, fucoidan and laminarin could induce the expression of M. amblycephala intelectin (MaINTL) in the primary hepatocytes and macrophages, and the recombinant MaINTL (rMaINTL) could bind with fucoidan and laminarin. Furthermore, fucoidan and laminarin induced the expression of cytoskeletal remodeling related genes in the primary M. amblycephala macrophages, such as Rac1 and WASP, which should contribute to the enhancement of seaweed polysaccharides (fucoidan and laminarin) and MaINTL on the phagocytosis of M. amblycephala macrophages. However, even though fucoidan and laminarin could induced the expression of CXCL8, while the chemotaxis of M. amblycephala macrophages on neutrophils was not affected by them. These findings suggested that fucoidan and laminarin enhanced the phagocytic capacity of M. amblycephala macrophages via activation of MaINTL and up-regulation of the expression of downstream cytoskeletal remodeling related genes Rac1 and WASP. Therefore, fucoidan and laminarin could be used as immune enhancers to improve host immunity and disease resistance in M. amblycephala, which provided novel insights into the prevention and protection of fish bacterial diseases.

The threat of bacterial septicemia caused by Aeromonas hydrophila infection to aquaculture growth can be prevented through vaccination, but differences among A. hydrophila strains may affect the effectiveness of non-conserved subunit vaccines or non-inactivated A. hydrophila vaccines, making the identification and development of conserved antigens crucial. In this study, a bioinformatics analysis of 4268 protein sequences encoded by the A. hydrophila J-1 strain whole genome was performed based on reverse vaccinology. The specific analysis included signal peptide prediction, transmembrane helical structure prediction, subcellular localization prediction, and antigenicity and adhesion evaluation, as well as interspecific and intraspecific homology comparison, thereby screening the 39 conserved proteins as candidate antigens for A. hydrophila vaccine. The 9 isolated A. hydrophila strains from diseased fish were categorized into 6 different molecular subtypes via enterobacterial repetitive intergenic consensus (ERIC)-PCR technology, and the coding regions of 39 identified candidate proteins were amplified via PCR and sequenced to verify their conservation in different subtypes of A. hydrophila and other Aeromonas species. In this way, conserved proteins were screened out according to the comparison results. Briefly, 16 proteins were highly conserved in different A. hydrophila subtypes, of which 2 proteins were highly conserved in Aeromonas species, which could be selected as candidate antigens for vaccines development, including type IV pilus secretin PilQ (AJE35401.1) and TolC family outer membrane protein (AJE35877.1). The present study screened the conserved antigens of A. hydrophila by using reverse vaccinology, which provided basic foundations for developing broad-spectrum protective vaccines of A. hydrophila.

Mannan oligosaccharides (MOS) have been studied and applied as a feed additive, whereas their regulation on the growth performance and immunity of aquatic animals lacks consensus. Furthermore, their immunoprotective effects on the freshwater fish Megalobrama amblycephala have not been sufficiently studied. Thus, we investigated the effects of dietary MOS of 0, 200, and 400 mg/kg on the growth performance, non-specific immunity, intestinal health, and resistance to Aeromonas hydrophila infection in juvenile M. amblycephala. The results showed that the weight gain rate of juvenile M. amblycephala was not significantly different after 8 weeks of feeding, whereas the feed conversion ratio decreased in the MOS group of 400 mg/kg. Moreover, dietary MOS increased the survival rate of juvenile M. amblycephala upon infection, which may be attributed to enhanced host immunity. For instance, dietary MOS increase host bactericidal and antioxidative abilities by regulating the activities of hepatic antimicrobial and antioxidant enzymes. In addition, MOS supplementation increased the number of intestinal goblet cells, and the intestine was protected from necrosis of the intestinal folds and disruption of the microvilli and junctional complexes, thus maintaining the stability of the intestinal epithelial barrier. The expression levels of M. amblycephala immune and tight junction-related genes increased after feeding dietary MOS for 8 weeks. However, the upregulated expression of immune and tight junction-related genes in the MOS supplemental groups was not as notable as that in the control group postinfection. Therefore, MOS supplementation might suppress the damage caused by excessive intestinal inflammation. Furthermore, dietary MOS affected the richness and composition of the gut microbiota, which improved the gut health of juvenile M. amblycephala by increasing the relative abundance of beneficial gut microbiota. Briefly, dietary MOS exhibited significant immune protective effects to juvenile M. amblycephala, which is a functional feed additive and immunostimulant.

Lipid was an essential constituent of aquatic feeds, among which fish oil (FO) was the most excellent lipid source for its nutritive values. However, high price and limited production restricted its application, thus leading to the consideration of developing other alternative lipid sources, and soybean oil (SO) instead of FO was applied as the main lipid source in the commercial feed of grass carp. In the present study, two typical lipids sources FO and SO were used to prepare grass carp feed, and their comparative effects on the growth performance, nutrient composition and metabolic signaling were investigated. The growth performance of two groups exhibited no significant difference, while crude lipid was much higher in the muscle of SO group. Additionally, muscle fatty acid composition of both groups were highly correlated with that of diets, and the proportion of muscle n-3 polyunsaturated fatty acids was notably higher in the FO group, especially that of C20:5n-3 (EPA) and C22:6n-3 (DHA). Comparative digital gene expression profiles (DGE) was conducted and 1261 differentially expressed genes (DEGs) had been identified, then gene ontology (GO) enrichment analysis revealed the enriched functional subterms were primarily focused on cellular metabolic processes and regulation. KEGG pathway analysis elucidated the main metabolism related pathways, and DEGs involved in fatty acid elongation, fatty acid metabolism, and glycerolipid metabolism pathways were listed, including elongation of very long chain fatty acids protein 7 (el7), lysophospholipid acyltransferase 4 (lpcat4), long-chain acyl-CoA synthetase (acs), phosphatidate phosphatase LPIN (lpin), cathepsin L, and glucose-6-phosphate isomerase (gpi) et al. In conclusion, the nutritional composition rather than growth performance of grass carp was affected by different lipid sources, and the underlying regulatory signaling was predicted, which would provide theoretical basis for fish diet formulation.

Fish in natural and cultivated environments can be challenged by starvation. However, inducing starvation in a controlled manner cannot only reduce feed consumption but also reduces aquatic eutrophication and even improves farmed fish quality. This study investigated the effects of starvation on the muscular function, morphology, and regulatory signaling in javelin goby (Synechogobius hasta) by evaluating the biochemical, histological, antioxidant, and transcriptional changes in the musculature of S. hasta subjected to 3, 7, and 14 days fasting. The muscle glycogen and triglyceride levels in S. hasta were gradually reduced under starvation, reaching their lowest at the end of the trial (P

Polychlorinated biphenyls (PCBs) are well-known persistent organic pollutants; they have toxic effects on the immune system, reproductive system, and endocrine system by changing the metabolism of the body. To elucidate the underlying molecular mechanism, the clam Meretrix meretrix was exposed to 10 and 1000 ng/L Aroclor 1254 and natural seawater (control). Samples from clams exposed to natural seawater and those exposed to Aroclor 1254 for 1 and 3 days were individually collected for transcriptome analysis. After assembly, more than 535,157 transcripts with a mean length of 949 bp and an N50 length of 1279 bp were obtained; a final set of 177,142 unigenes was generated. In the present study, 5101 differentially expressed genes were identified. The differentially expressed genes were related to detoxification metabolism, oxidative stress, immune response, and endocrine system disruption. Of these genes, under the Aroclor 1254 exposure, cytochrome P450 20A1 (2.06–4.46 folds), glutathione S-transferase (2.25–3.80 folds), multidrug resistance-associated protein 1-like (1.49–2.92 folds), peroxidase-like protein (1.33–4.26 folds), lysozyme (1.61–2.05 folds), bcl-2 like 1 protein (1.14–2.29 folds) and vitellogenin (1.09–1.19 folds) showed been significantly induced expressed. At the same time, some genes were down regulated, including cytochrome P450 2J5 (−1.20 ~ −2.86 folds), cytochrome P450 3A24 (−1.40 ~ −4.08 folds), C1q (−1.27 ~ −1.66 folds), Sulfotransferase (−1.51 ~ −1.84 folds), monocarboxylate transporter 10 (−1.30 ~ −4.70 folds), 3-beta hydroxysteroid dehydrogenase (−1.43 ~ −2.81 folds) and beta-galactosidase (−1.23 ~ −2.23 folds). Furthermore, it showed that the expression levels of CYP2J5, glutathione S-transferase, 3-beta hydroxysteroid dehydrogenase and beta-galactosidase had time responses and dose responses. The present study provided insights into the toxic effects of Aroclor 1254 exposure in M. meretrix.

Macrobrachium rosenbergii de Man, 1879 (Caridea: Palaemonidae), commonly referred to as giant freshwater prawn, is commercially important worldwide, and a primary inland cultured species. The first complete mitochondrial genome of M. rosenbergii from China (CN) was sequenced and compared with that in Indonesia (ID) in this study. The results show that the total length of CN-mtDNA sequence is 15,767 bp (GenBank accession number: KY865098), which is shorter than that of ID-mtDNA (15,772 bp). It encodes 37 genes, including 13 protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes. The heavy strand and light strand encode 23 and 14 genes, respectively, and the content of A + T is 61.81%. The gene order and content of CN-mtDNA and ID-mtDNA are identical to the primitive Pancrustacean ground pattern. Phylogenetic analysis shows that CN-mtDNA is clustered into one clade with ID-mtDNA (BP =100). Pairwise genetic distance analyses indicate that the genetic distance of CN-mtDNA and ID-mtDNA is 0.086, which is smaller than values between species in the Macrobrachium genus. In summary, both phylogenetic analysis and gene re-arrrangement analysis between the M. rosenbergii in China and Indonesia have revealed that their differences are within intraspecific variation.

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