NinaB and BCO Collaboratively Participate in the ß-Carotene Catabolism in Crustaceans: A Case Study on Chinese Mitten Crab Eriocheir sinensis.

Carotenoid cleavage oxygenases can cleave carotenoids into a range of biologically important products. Carotenoid isomerooxygenase (NinaB) and ß, ß-carotene 15, 15'-monooxygenase (BCO1) are two important oxygenases. In order to understand the roles that both oxygenases exert in crustaceans, we first investigated NinaB-like (EsNinaBl) and BCO1-like (EsBCO1l) within the genome of Chinese mitten crab (Eriocheir sinensis). Their functions were then deciphered through an analysis of their expression patterns, an in vitro ß-carotene degradation assay, and RNA interference. The results showed that both EsNinaBl and EsBCO1l contain an RPE65 domain and exhibit high levels of expression in the hepatopancreas. During the molting stage, EsNinaBl exhibited significant upregulation in stage C, whereas EsBCO1l showed significantly higher expression levels at stage AB. Moreover, dietary supplementation with ß-carotene resulted in a notable increase in the expression of EsNinaBl and EsBCO1l in the hepatopancreas. Further functional assays showed that the EsNinaBl expressed in E. coli underwent significant changes in its color, from orange to light; in addition, its ß-carotene cleavage was higher than that of EsBCO1l. After the knockdown of EsNinaBl or EsBCO1l in juvenile E. sinensis, the expression levels of both genes were significantly decreased in the hepatopancreas, accompanied by a notable increase in the redness (a*) values. Furthermore, a significant increase in the ß-carotene content was observed in the hepatopancreas when EsNinaBl-mRNA was suppressed, which suggests that EsNinaBl plays an important role in carotenoid cleavage, specifically ß-carotene. In conclusion, our findings suggest that EsNinaBl and EsBCO1l may exhibit functional co-expression and play a crucial role in carotenoid cleavage in crabs.

Comparative Analyses of Scylla olivacea Gut Microbiota Composition and Function Suggest the Capacity for Polyunsaturated Fatty Acid Biosynthesis.

Although numerous studies in aquatic organisms have linked lipid metabolism with intestinal bacterial structure, the possibility of the gut microbiota participating in the biosynthesis of beneficial long-chain polyunsaturated fatty acid (LC-PUFA) remains vague. We profiled the gut microbiota of the mud crab Scylla olivacea fed with either a LC-PUFA rich (FO) or a LC-PUFA-poor but C18-PUFA substrate-rich (LOCO) diet. Additionally, a diet with a similar profile as LOCO but with the inclusion of an antibiotic, oxolinic acid (LOCOAB), was also used to further demarcate the possibility of LC-PUFA biosynthesis in gut microbiota. Compared to diet FO treatment, crabs fed diet LOCO contained a higher proportion of Proteobacteria, notably two known taxonomy groups with PUFA biosynthesis capacity, Vibrio and Shewanella. Annotation of metagenomic datasets also revealed enrichment in the KEGG pathway of unsaturated fatty acid biosynthesis and polyketide synthase-like system sequences with this diet. Intriguingly, diet LOCOAB impeded the presence of Vibrio and Shewanella and with it, the function of unsaturated fatty acid biosynthesis. However, there was an increase in the function of short-chain fatty acid production, accompanied by a shift towards the abundance of phyla Bacteroidota and Spirochaetota. Collectively, these results exemplified bacterial communities and their corresponding PUFA biosynthesis pathways in the microbiota of an aquatic crustacean species.

Functional transcriptome reveals hepatopancreatic lipid metabolism during the molting cycle of the Chinese mitten crab Eriocheir sinensis.

Crustacean molting is highly related to energy and lipid metabolism. This study was conducted to detect the changes of total lipids (TL), triacylglyceride (TAG), phospholipid (PL) and lipid droplets in hepatopancreas, and then to investigate the gene expression patterns related to hepatopancreatic lipid metabolism during the molting cycle of Chinese mitten crab Eriocheir sinensis. Hepatopancreatic TL and TAG increased significantly from post-molt stage to pre-molt stage, then decreased significantly from pre-molt stage to ecdysis stage, which is consistent to the changes of neutral lipid-rich adipocytes in hepatopancreas. By transcriptomic analysis, 65,325 transcripts were sequenced and assembled, and 28,033 transcripts were annotated. Most genes were related to energy metabolism, and the enriched genes were involved in carbohydrate and lipid metabolism and biosynthesis, especially in de novo synthesis of fatty acids and TAG, and ketone body production. Compared to the inter-molt stages, acetyl-CoA carboxylase, fatty acid synthase and other genes related to the synthesis of fatty acids were upregulated in the pre-molt stage. TAG synthesis related genes, including Glycerol-3-phosphate acyltransferase and 1-acylglycerol-3-phosphate acyltransferases, were upregulated in the post-molt stage compared to the inter-molt stage. The expression of ketone body-related genes had no significant changes during the molting cycle. Compared to the TAG synthetic pathway, ketone body biosynthesis may contribute less/secondarily to fatty acid metabolic processes, which could be involved in the other physiological processes or metabolism. In conclusion, these results showed that TAG is the major lipid deposition during inter- and pre-molt stages, and the most genes are related to the fatty acids and TAG metabolism in the hepatopancreas during the molting cycle of E. sinensis.

Genome-Wide Analysis Indicates a Complete Prostaglandin Pathway from Synthesis to Inactivation in Pacific White Shrimp, Litopenaeus vannamei.

Prostaglandins (PGs) play many essential roles in the development, immunity, metabolism, and reproduction of animals. In vertebrates, arachidonic acid (ARA) is generally converted to prostaglandin G2 (PGG2) and H2 (PGH2) by cyclooxygenase (COX); then, various biologically active PGs are produced through different downstream prostaglandin synthases (PGSs), while PGs are inactivated by 15-hydroxyprostaglandin dehydrogenase (PGDH). However, there is very limited knowledge of the PG biochemical pathways in invertebrates, particularly for crustaceans. In this study, nine genes involved in the prostaglandin pathway, including a COX, seven PGSs (PGES, PGES2, PGDS1/2, PGFS, AKR1C3, and TXA2S), and a PGDH were identified based on the Pacific white shrimp (Litopenaeus vannamei) genome, indicating a more complete PG pathway from synthesis to inactivation in crustaceans than in insects and mollusks. The homologous genes are conserved in amino acid sequences and structural domains, similar to those of related species. The expression patterns of these genes were further analyzed in a variety of tissues and developmental processes by RNA sequencing and quantitative real-time PCR. The mRNA expression of PGES was relatively stable in various tissues, while other genes were specifically expressed in distant tissues. During embryo development to post-larvae, COX, PGDS1, GDS2, and AKR1C3 expressions increased significantly, and increasing trends were also observed on PGES, PGDS2, and AKR1C3 at the post-molting stage. During the ovarian maturation, decreasing trends were found on PGES1, PGDS2, and PGDH in the hepatopancreas, but all gene expressions remained relatively stable in ovaries. In conclusion, this study provides basic knowledge for the synthesis and inactivation pathway of PG in crustaceans, which may contribute to the understanding of their regulatory mechanism in ontogenetic development and reproduction.

Comparative study of female Chinese mitten crabs based on their sizes and weights.

The Chinese mitten crab (Eriocheir sinensis) is an important aquaculture species in China. While the price of a large crab will generally be 2-5 times higher than that of smaller crabs, it remains unknown whether nutritional quality is affected by market price. To investigate the effect of size on nutritional composition, adult female crabs were collected and assigned to grades I-IV according to decreasing size. The results showed that meat yield and conditional factors were significantly (P < 0.05) reduced with the decreasing size. The different sizes did not significantly (P > 0.05) affect levels of moisture, crude protein (except for hepatopancreatic crude protein), and total lipid. Grade III crabs had the largest hepatopancreatic crude protein level, which was significantly (P < 0.05) increased compared with grade I crabs. A balanced amino acid composition was found in grade IV crabs, while crabs from grades II and IV had the highest essential amino acids score. Levels of highly unsaturated fatty acids, including C22:6n3, and the ratios of n-3 polyunsaturated fatty acids (PUFA)/n-6 PUFA and C22:6n3 (DHA)/C20:5n3 (EPA) in the hepatopancreas were significantly (P < 0.05) increased in grade III crabs compared with the other grades. In conclusion, among the four grades smaller female crabs (average weight: 93-112 g, grades III-IV) displayed an optimal nutritional quality.

Ovarian development pattern and vitellogenesis of ridgetail white prawn, Exopalaemon carinicauda.

The ridgetail white prawn Exopalaemon carinicauda has the potential to be used as a model organism in crustacean research because it has a transparent body, available draft genome, and short life cycle. However, their ovarian development pattern remains unclear under laboratory culture conditions. This study investigated the changes of ovarian external feature, ovarian histology, gonadosomatic index (GSI), and hepatosomatic index (HSI), as well as the expression and localization of vitellogenin in the ovary and the hepatopancreas during the first ovarian development cycle of E. carinicauda under laboratory-reared condition. The results demonstrated that (1) the first ovarian development cycle of E. carinicauda could be divided into 5 different stages in which the ovary changes its color from white to yellow during the vitellogenesis process in parallel with increasing GSI. (2) After pubertal molt, most females reached ovarian stage II while the females reached stage V after premating molt. (3) During the ovarian development, GSI increased smoothly and HSI relatively stable during the period of stages I to IV, while GSI increased but HSI decreased significantly from stages IV to V. (4) In situ hybridization (ISH) revealed that EcVg was slightly expressed in the oocyte cytoplasm of previtellogenic oocytes. The positive signal was mainly detected in hepatopancreatic fibrillar cells, and a strong signal was found in the hepatopancreas at stage IV. Moreover, the expression level of EcVg-mRNA in the hepatopancreas is stage-specific, and the hepatopancreas contributes majority of vitellin precursor protein to support the ovarian development of E. carinicauda.

Micro-algal astaxanthin could improve the antioxidant capability, immunity and ammonia resistance of juvenile Chinese mitten crab, Eriocheir sinensis.

Green alga Haematococcus pluvialis is an important source of natural astaxanthin (Ast), which have been shown to be beneficial for the color formulation, survival, antioxidation, immunity and stress resistance of many crustacean. This study was conducted to investigate the effects of dietary supplementation of H. pluvialis meal on growth, antioxidant status, ammonia resistance, color parameters, and carotenoids composition of juvenile Chinese mitten crab Eriocheir sinensis. Five diets were formulated to contain 0, 30, 60, 90 and 120 mg/kg dry diets of natural Ast (defined as Diet 1-5) using H. pluvialis meal as astaxanthin source. The results showed that: (1) Although all treatments with Ast supplementation had the relatively higher growth performance and survival than the control (Diet 1 treatment), no significant differences were found on growth performance, feed conversion ratio and hepatosomatic index among all treatments. (2) The highest total antioxidant capacity (T-AOC) in hepatopancreas and hemolymph were observed in Diet 4 and 3 treatments respectively, while the lowest malondialdehyde (MDA) contents in hepatopancreas and hemolymph were also found in these two treatments. Furthermore, the significantly positive relationships were detected on acid phosphatase (ACP) activities and dietary Ast contents for hepatopancreas and hemolymph. (3) Diet 3 treatment had the highest mRNA levels of EsLecA, EsTrx, and EsPrx6 in hepatopancreas, while both Diet 3 and 4 treatments reached the peaks for mRNA expression levels of EsMyd88 and EsHc, respectively. (4) The stress test with ammonia-N indicated Diet 1 treatment had the highest mortality among all treatments, and the lowest mortality was found on Diet 3 treatment during the stress test. (5) Dietary Ast significantly improved the redness (a*) of carapace and hepatopancreas, which were consistent with the Ast contents in these tissues from the different treatments. Ast concentrations in carapace reached the plateau for Diet 3 treatment while hepatopancreatic Ast concentration kept increasing with elevating dietary Ast contents. In conclusion, natural astaxanthin could enhance the antioxidative capability, non-specific immunity, tissue Ast contents and stress resistance to ammonia-N, and these results suggested the optimal diet micro-algal astaxanthin was around 60 mg/kg for juvenile E. sinensis.

Transcriptome analysis reveals the potential mechanism of dietary carotenoids improving antioxidative capability and immunity of juvenile Chinese mitten crabs Eriocheir sinensis.

Carotenoids are known to be involved in the regulation of the antioxidative capability, immune response and stress resistance in crustacean species; however, very limited information is available on their underlying molecular mechanisms. This study performed transcriptome sequencing of hemolymph and hepatopancreas of juvenile Chinese mitten crabs (Eriocheir sinensis) that fed with three diets, i.e. diet A containing 90 mg kg-1 dry weight of astaxanthin, diet B containing 200 mg kg-1 dry weight of ß-carotene and control diet without supplementation of dietary carotenoids. The results showed that there were 2955 and 497 differentially expressed genes (DEGs) in the hemolymph between the astaxanthin treatment and control groups, and between the ß-carotene treatment and control groups, respectively. Moreover, compared with the control group, 833 and 1886 DEGs were obtained in the hepatopancreas of the astaxanthin treatment and the ß-carotene treatment groups, respectively. The DEGs in the three groups were enriched in 255 specific KEGG metabolic pathways according to KEGG enrichment analysis. Through this study, a series of key genes involved in Nrf2 signalling, ROS production, intracellular antioxidant enzymes and chaperones were significantly affected by dietary carotenoids. Dietary carotenoids also significantly altered the expression levels of immune-related molecules associated with signal transduction, prophenoloxidase cascade, apoptosis, pattern recognition proteins/receptors and antimicrobial peptides. In conclusion, this transcriptomic study provides valuable information for understanding the molecular mechanism and potential pathway of dietary carotenoids improved the antioxidative capability and immunity of juvenile E. sinensis.

TMT-based quantitative proteomic analysis of Eriocheir sinensis hemocytes and thoracic ganglion during Spiroplasma eriocheiris infection.

Spiroplasma eriocheiris, a novel pathogen of Chinese mitten crab Eriocheir sinensis tremor disease, has led into catastrophic economic losses in aquaculture. S. eriocheiris invaded the hemocytes in the early stage, then invaded nerve tissue and caused typically paroxysmal tremors of pereiopod in the late stage of infection. The purpose of this study was to detect the infection mechanism of hemocytes in the early stage and thoracic ganglion in the late stage of S. eriocheiris infection at the protein level. Hemocytes and thoracic ganglion were collected at 24 h and 10 d after injection (the crabs with typical paroxysmal tremors of the pereiopod), respectively. TMT was performed with isobaric markers, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). In hemocytes, 127 proteins were up-regulated and 85 proteins were down-regulated in 2747 quantified proteins. Many proteins and process including proPO system proteins, hemolymph coagulation system proteins and lectins were differently expressed in hemocytes and involved in the early immune process of E. sinensis against S. eriocheiris infection. Meanwhile, 545 significantly different expression proteins (292 down-regulated and 253 up-regulated protein including a number of immune-associated, nervous system development and signal transmission related proteins) were identified in thoracic ganglion in the late stage of S. eriocheiris infection. The qRT-PCR analysis results shown that the selected significantly changed proteins in hemocytes and thoracic ganglion were consistent with the TMT proteomics. This paper reported for the first time to study the responses of crab hemocyte and thoracic ganglion against the S. eriocheiris infection at different stages. These findings help us understand the infection mechanism of S. eriocheiris at different stage with the different tissue.

Functional expression patterns of four ecdysteroid receptor isoforms indicate their different functions during vitellogenesis of Chinese mitten crab, Eriocheir sinensis.

In arthropods, alternative splicing of ecdysteroid receptor gene (EcR) leads to multiple functions of different EcR isoforms during metamorphosis, growth and ovarian development via ecdysteroid signaling pathway. This study was conducted to investigate the expression patterns of four EcRs of Eriocheir sinensis (EsEcRs) and the changes of haemolymph ecdysteroid titer during the ovarian development. The results showed that four EsEcR isoforms had the tissue-specific expression among 12 examined tissues, and the highest transcript levels of the four EsEcR isoforms were detected in Y-organ or sinus gland. During the ovarian development, EsEcR1 showed the highest transcript abundance of the four EsEcR isoforms. The expression profiles of all the EsEcR isoforms were similar in the hepatopancreas during the ovarian maturation cycle of E. sinensis with a trend of "high-low-high-low". In ovary, the highest expression levels of EsEcR1 and EsEcR4 were both found at stage V ovary, while the peaks of EsEcR2 and EsEcR3 were found on stage III ovary and stage IV ovary, respectively. Meanwhile, the ecdysteroid titer in haemolymph decreased gradually during ovarian maturation cycle. Further regression analysis revealed significant negative correlations were found between the ovarian EsEcR3/ EsEcR4 expression levels and haemolymph ecdysteroid titer during part or whole ovarian development cycle. These results together indicated that four EsEcR isoforms may have different functions during ovary maturation of E. sinensis. All EcR isoforms and ecdysteroid seemed to have important roles in the hepatopancreas during early ovarian development stages, while EsEcR3 and EsEcR4 were closely related to the mid-late vitellogenesis stages.

Effect of estradiol on hepatopancreatic lipid metabolism in the swimming crab, Portunus trituberculatus.

Estradiol is an important sex steroid hormone that involved in regulation of animal lipid metabolism. However, the effect of estradiol on lipid metabolism in swimming crab (Portunus trituberculatus) is unclear. The present study investigated the effect of four concentrations of exogenous estradiol (0, 0.01, 0.1 and 1 µg g-1 crab weight) on the expression levels of lipid metabolism-related genes, lipid composition and histology of hepatopancreas in the P. trituberculatus. The results showed that the mRNA levels of carnitine palmitoyltransferase I and II (CPT-I and CPT-II) increased significantly at the low concentrations (0.01 µg g-1 and 0.1 µg g-1), while decreased significantly in the highest concentration (1 µg g-1). The mRNA levels of acyl-CoA oxidase (ACOX), fatty acid transport protein (FATP), fatty acid-binding protein (FABP), diacylglycerol acyltransferase 1 (DGAT1) and acetyl-CoA carboxylase (ACC) were significantly down-regulated. The transcripts of fatty acid synthase (FAS) and fatty acyl desaturase (FAD) decreased significantly only in 1 µg g-1 treatment. All estradiol treatments (0.01, 0.1 and 1 µg g-1) had significantly higher percentages of 20:4n6, 20:5n3 and 22:6n3, but lower percentages of total monounsaturated fatty acids and polar lipids than the control treatment (0 µg g-1). Histological observations indicated the size of B cell became larger under estradiol treatment. The results indicated that estradiol promoted lipid catabolism in the hepatopancreas of P. trituberculatus.

Evaluating expression of autophagy-related genes in oriental river prawn Macrobrachium nipponense as potential biomarkers for hypoxia exposure.

Autophagy, a crucial process for maintaining cellular homeostasis, is under the control of several autophagy-related (ATG) proteins, and is highly conserved in most animals, but its response to adverse environmental conditions is poorly understood in crustaceans. Herein, we hypothesised that autophagy acts as a protective response to hypoxia, and Beclin 1, ATG7 and ATG8 in oriental river prawn (Macrobrachium nipponense) were chosen as potential biomarkers under hypoxia exposure; thus, their full-length cDNA sequences were cloned and characterised. Open reading frames (ORFs) of 1281, 2076 and 360 bp, encoding proteins of 427, 692 and 120 amino acid residues, respectively, were obtained. Phylogenetic analysis demonstrated the three M. nipponense proteins do not form a clade with vertebrate homologs. Protein and mRNA levels were investigated in different tissues and developmental stages, and all three were significantly upregulated in a time-dependent manner in the hepatopancreas following hypoxia stress. Biochemical and morphological analysis of hepatocytes revealed that hypoxia increased the abundance of hepatic autophagic vacuoles and stimulated anaerobic metabolism. RNA interference-mediated silencing of ATG8 significantly increased the death rate of M. nipponense juveniles under hypoxia stress conditions. Together, these results suggest that Beclin 1, ATG7 and ATG8 contribute to autophagy-based responses against hypoxia in M. nipponense. The findings also expand our understanding of the potential role of autophagy as an adaptive response against hypoxia toxicity in crustaceans. The results showed that hepatic ATG8 levels may be directly indicative of acute hypoxia in prawns, and provide insight into the time at which hypoxia exposure occurs. Autophagy-related genes expression pattern seems to be sensitive and good biomarkers of acute hypoxia exposure.

Identification and Characterization of Four Autophagy-Related Genes That Are Expressed in Response to Hypoxia in the Brain of the Oriental River Prawn (Macrobrachium nipponense).

Autophagy is a cytoprotective mechanism triggered in response to adverse environmental conditions. Herein, we investigated the autophagy process in the oriental river prawn (Macrobrachium nipponense) following hypoxia. Full-length cDNAs encoding autophagy-related genes (ATGs) ATG3, ATG4B, ATG5, and ATG9A were cloned, and transcription following hypoxia was explored in different tissues and developmental stages. The ATG3, ATG4B, ATG5, and ATG9A cDNAs include open reading frames encoding proteins of 319, 264, 268, and 828 amino acids, respectively. The four M. nipponense proteins clustered separately from vertebrate homologs in phylogenetic analysis. All four mRNAs were expressed in various tissues, with highest levels in brain and hepatopancreas. Hypoxia up-regulated all four mRNAs in a time-dependent manner. Thus, these genes may contribute to autophagy-based responses against hypoxia in M. nipponense. Biochemical analysis revealed that hypoxia stimulated anaerobic metabolism in the brain tissue. Furthermore, in situ hybridization experiments revealed that ATG4B was mainly expressed in the secretory and astrocyte cells of the brain. Silencing of ATG4B down-regulated ATG8 and decreased cell viability in juvenile prawn brains following hypoxia. Thus, autophagy is an adaptive response protecting against hypoxia in M. nipponense and possibly other crustaceans. Recombinant MnATG4B could interact with recombinant MnATG8, but the GST protein could not bind to MnATG8. These findings provide us with a better understanding of the fundamental mechanisms of autophagy in prawns.

Correction to: Immunolocalization and changes of 17beta-estradiol during ovarian development of Chinese mitten crab Eriocheir sinensis.

The published online version contains mistake in Title and in Acknowledgement section. Please find below for the needed corrections.

Immunolocalization and changes of 17beta-estradiol during ovarian development of Chinese mitten crab Eriocheir sinensis' [corrected].

17beta-estradiol (E2) is important for crustacean ovarian development. This study aims to investigate the distribution and change pattern of E2 in the ovary, hepatopancreas, thoracic ganglion and brain ganglion as well as Vg-mRNA expression level during ovarian development of Chinese mitten crab Eriocheir sinensis. Results showed that strongly positive signals of E2 were mainly distributed in follicle cells of ovaries for all developmental stages as well as oocyte cytoplasm of stages III to V ovaries. In hepatopancreas, the E2-positive signal was mainly detected in the cytoplasm and nucleus of fibrillar cells and the nucleus of resorptive cells, while the maximum fluorescence intensity was observed in stage III hepatopancreas. On the contrary, the E2 immunoreactivities in nervous tissues were relatively stable during ovarian development. Moreover, the changing pattern of E2 concentration was similar within hemolymph, ovary and hepatopancreas during the ovarian development. From stages I to III, the E2 content in three tissues increased significantly, then decreased gradually until stage V. As for the Vg-mRNA expression level in hepatopancreas and ovaries, an increasing trend was found in ovaries but no significant difference was detected during the period of ovarian stages III to V. Hepatopancreatic Vg-mRNA expression level increased significantly during stages I to IV and dramatically decreased at stage V. In conclusion, our study suggests that ovary, hepatopancreas, hemolymph and nervous tissues are the target organs of E2 in E. sinensis and E2 concentrations in different tissues are closely related to vitellogenesis in ovary and hepatopancreas during ovarian development.

Molecular Cloning and Expression Analysis of Lactate Dehydrogenase from the Oriental River Prawn Macrobrachium nipponense in Response to Hypoxia.

Metabolic adaption to hypoxic stress in crustaceans implies a shift from aerobic to anaerobic metabolism. Lactate dehydrogenase (LDH) is a key enzyme in glycolysis in prawns. However, very little is known about the role of LDH in hypoxia inducible factor (HIF) pathways of prawns. In this study, full-length cDNA of LDH (MnLDH) was obtained from the oriental river prawn Macrobrachium nipponense, and was characterized. The full-length cDNA is 2267-bp with an open reading frame of 999 bp coding for a protein of 333 amino acids with conserved domains important for function and regulation. Phylogenetic analysis showed that MnLDH is close to LDHs from other invertebrates. Quantitative real-time PCR revealed that MnLDH is expressed in various tissues with the highest expression level in muscle. MnLDH mRNA transcript and protein abundance in muscle, but not in hepatopancreas, were induced by hypoxia. Silencing of hypoxia-inducible factor 1 (HIF-1) α or HIF-1ß subunits blocked the hypoxia-dependent increase of LDH expression and enzyme activity in muscle. A series of MnLDH promoter sequences, especially the full-length promoter, generated an increase in luciferase expression relative to promoterless vector; furthermore, the expression of luciferase was induced by hypoxia. These results demonstrate that MnLDH is probably involved a HIF-1-dependent pathway during hypoxia in the highly active metabolism of muscle.

Nondestructive prediction and visualization of plumpness in live Eriocheir sinensis using low-field 1 H magnetic resonance imaging.

BACKGROUND: The plumpness of hepatopancreas and gonad tissues in live Chinese mitten crabs (Eriocheir sinensis) depends on the grading scale and its commercial value. In this work, a low-field T1 -weighted 1 H magnetic resonance imaging (LF-1 H MRI) technique was developed to nondestructively analyze the plumpness of hepatopancreas and gonad tissues in live E. sinensis. Both male and female E. sinensis were characterized by two-dimensional (2D) LF-1 H MRI. Moreover, a three-dimensional (3D) LF-1 H MRI model that quantitatively integrated the total volume of lipid tissues in live E. sinensis was used. RESULTS: The results showed 2D LF-1 H MRI could accurately discriminate the plumpness of hepatopancreas and gonad tissues in live E. sinensis. The results of the 3D LF-1 H MRI model displayed that the lipid volume of E. sinensis could be used to quantify lipid accumulation in lipid tissues. CONCLUSION: LF-1 H MRI technology was successfully developed to accurately discriminate the development of E. sinensis hepatopancreas and gonad tissues in a nondestructive manner, indicating its application potential in grading commercial live crabs or advising crab farmers on breeding and fattening processes. © 2018 Society of Chemical Industry.

Nutritional quality of different grades of adult male chinese mitten crab, Eriocheir sinensis.

This study mainly investigated the composition of adult male Chinese mitten crab (Eriocheir sinensis) from four grades/sizes (Grade I: 200-249 g; Grade II: 175-199 g; Grade III: 150-174 g; Grade IV: ≤ 150 g). The results showed that the grade III crabs had the largest gonadsomatic index (GSI), which was significantly higher than the grade I and grade II crabs, no significant difference was found with the grade IV crab. Significant differences in moisture and total lipid contents were observed among various edible parts from different grades of male Eriocheir sinensis. In particular, grade II crabs had the highest total lipid and dry matter content for hepatopancreas. A balanced amino acids composition and a high essential amino acids score (EAAS) were found in the muscle and gonads of grade III crabs. The levels of poly-unsaturated fatty acids (PUFA), n-3 PUFA, n-6 PUFA and docosahexaenoic acid (DHA) in the hepatopancreas, as well as the contents of PUFA, highly-unsaturated fatty acids (HUFA), n-3 PUFA, arachidonic acid (ARA), and eicosapentaenoic acid (EPA) in the gonads were significantly increased in the grade II crabs. Taken together, it can generally be concluded that adult male Eriocheir sinensis of 150-200 g (Grade II-III) weight have the highest nutritional quality even though they are not the largest crabs.

Molecular cloning, characterization and expression analysis of caspase-3 from the oriental river prawn, Macrobrachium nipponense when exposed to acute hypoxia and reoxygenation.

Caspases are present in the cytosol as inactive proenzymes but become activated when apoptosis is initiated, playing an essential role at various stages of the process. In this study, a caspase-3 (Mncaspase-3c) was cloned from gill of the oriental river prawn Macrobrachium nipponense by reverse-transcription polymerase chain reaction and rapid amplification of cDNA ends, and its properties were characterized. The 1730-bp cDNA contained an open reading frame of 1566 bp, a 123-bp 5'-untranslated region (UTR), and a 41-bp 3'-UTR containing a poly(A) tail. The molecular mass of the deduced amino acid (aa) sequence (521 aa) was 56.3 kDa with an estimated pI of 5.01. The MnCaspase-3c sequence contained a predicted caspase family p20 domain and a caspase family p10 domain at positions 236-367 and 378-468 respectively. Recombinant MnCaspase-3c protein was expressed in Escherichia coli and purified. In vitro activity assays indicated that the recombinant MnCaspase-3c hydrolyzed the substrate Ac-DEVD-pNA, suggesting a physiological role as a caspase-3. Caspase-3c gene transcripts were distributed in all M. nipponense tissues tested by quantitative RT-PCR, being especially abundant in hemocytes. Comet assays in gill tissues showed an obvious time-dependent response to hypoxia. Furthermore, Mncaspase-3c, at both the mRNA and protein levels, was demonstrated to participate in the apoptotic process in gill after stimulation by acute hypoxia. Overall, these results indicate that hypoxia triggers apoptosis in shrimp gill tissues.