Effects of using the biofloc system and eyestalk ablation on reproductive performance and egg quality of Litopenaeus vannamei (Boone, 1931) (Decapoda: Dendrobranchiata: Penaeidae).

The aim of this study was to evaluate egg production and quality of females of the Pacific white shrimp, Litopenaeus vannamei, in which there was or was not unilateral eyestalk ablation after there was pre-maturation culturing in biofloc or clear-water systems. Acylglycerides, cholesterol, glucose and total soluble protein were determined for the hepatopancreas, ovaries, hemolymph and eggs. Females cultured using the biofloc system had a larger number of eggs released per spawning and per gram of spawning specimen body weight. The number of total spawning's per week was comparable among treatments. Females cultured in the biofloc system in which there was no eyestalk ablation had that greatest concentrations of nutrient reserves in the hepatopancreas (P < 0.05) with the females cultured in the biofloc and clear-water system that had eye stalk ablation having the next most abundant nutrient reserves. There were the least concentrations of nutrient reserves in females with eyestalk ablation cultured in the clear-water system (P < 0.05). There, however, were no difference in nutrient reserve concentrations in the hemolymph and ovaries. In the eggs, there was the same trend among treatments as the hepatopancreas nutrient reserves, indicating that both eyestalk ablation and pre-maturation culture conditions (i.e., either biofloc or clear-water) affected the quality of eggs in L. vannamei.

The immune function of a novel crustin with an atypical WAP domain in regulating intestinal microbiota homeostasis in Litopenaeus vannamei.

Crustins are a family of antimicrobial peptides (AMP) with multiple functions, including antimicrobial activity, capability of protease inhibition, phagocytosis promotion, and wound healing in crustaceans. Till present, several members of crustins have been identified and their activities were studied. However, there are still less investigations on how they play functions in vivo. Here, we identified a novel crustin with an atypical WAP domain, LvCrustin Ⅰ-1, which is mainly distributed in tissues, including intestine, gill, epidermis and stomach of the shrimp Litopenaeus vannamei. The expression level of LvCrustin Ⅰ-1 was significantly up-regulated at 3 h, 6 h, 12 h, and 24 h after Vibrio parahaemolyticus infection. Knockdown of LvCrustin Ⅰ-1 with dsRNA resulted in a significant increase of the bacteria number in hepatopancreas of shrimp upon V. parahaemolyticus infection, showing that LvCrustin Ⅰ-1 participated in pathogen infection process. Recombinant LvCrustin Ⅰ-1 protein showed microorganism-binding activity rather than antibacterial activity against tested bacteria. Furthermore, significant difference existed between the intestinal microbiota in shrimp before and after LvCrustin Ⅰ-1 knockdown based on the result of alpha and NMDS analyses. Knockdown of LvCrustin Ⅰ-1 increased the proportion of Demequina, Nautella, Propionibacterium, Anaerospora and decreased the proportion of Bacteroidia and Vibrio. These data suggest that LvCrustin Ⅰ-1 might perform its immunological function through modulation of the intestinal microbiota homeostasis rather than direct inhibition of bacterial growth in shrimp.

Molecular characterization of a heat shock protein 21 (Hsp21) from red swamp crayfish, Procambarus clarkii in response to immune stimulation.

Small heat shock proteins are a molecular chaperone and implicated in various physiological and stress processes in animals. However, the immunological functions of Hsp genes remain to elucidate in the crustaceans, particularly in red swamp crayfish, Procambarus clarkii. Here we report the cloning of heat shock protein 21 from the P. clarkii (hereafter Pc-Hsp21). The open reading frame of Pc-Hsp21 was 555 base pairs, encoding a protein of 184 amino acid residues with an alpha-crystallin family domain. Quantitative real-time PCR (qRT-PCR) analysis revealed a constitutive transcript expression of Pc-Hsp21 in the tested tissue, with the highest in hepatopancreas. The transcript abundance for this gene enhanced in hepatopancreas following immune challenge with the lipopolysaccharide, peptidoglycan, and poly I:C compared to the control group. The depletion of Pc-Hsp21 by double-stranded RNA altered transcript expression profiles of several genes in hepatopancreas, genes involved in the crucial immunological pathways of P. clarkii. These results suggest that Pc-Hsp21 plays an essential biological role in the microbial stress response by modulating the expression of immune-related genes in P. clarkii.

Heat shock protein 20 from Procambarus clarkii is involved in the innate immune responses against microbial infection.

Small heat shock proteins (shsps) are conserved across invertebrate species. They are implicated in the modulation of various biological processes, such as immune responses, abiotic stress tolerance metamorphosis, and embryonic development. Herein, we identified a heat shock protein 20 from the red swamp crayfish, Procambarus clarkii (named as Pc-Hsp20), and performed in vivo studies to elucidate its physiological functions in the innate immunity. The open reading frame of Pc-Hsp20 was 609 base pair, encoding a protein of 202 amino acid residues with a hsp20/alpha crystallin family domain. Pc-Hsp20 was ubiquitously expressed in various tissues; however, it was highest in the hepatopancreas. The challenge with immune elicitors remarkably enhanced the transcript level of Pc-Hsp20 in the hepatopancreas when compared with the control. Administration of double-stranded RNA could significantly reduce expression of the Pc-Hsp20 mRNAs, and most of the immune-related genes expression enhanced with a variable concentration in the hepatopancreas. Altogether, these results suggest that Pc-Hsp20 may participate in innate immunity against microbial pathogens.

Molecular and expression characterization of Toll-like receptor family genes from the Anadara sativa (Bivalvia, Arcidae) transcriptome.

Innate immunity plays an important role in invertebrates because it provides the first line of protection by recognizing invading microbial pathogens and then activating downstream signaling pathways. However, until now, increasing reports of clam diseases did not include those of Anadara sativa, which are widely distributed and economically important maritime clams. In the present study, transcriptome libraries of untreated (termed H) and Vibrio anguillarum-challenged (termed HV) A. sativa hepatopancreases were constructed and sequenced using the Illumina HiSeq4000 platform. In total, we obtained 78,012,510 and 84,937,516 clean reads from 80,006,030 to 86,871,742 raw data reads, respectively, assembled by different software programs. Furthermore, 150,274 unigenes were generated from 196,003 transcripts, with an N50 length of 1088 bp, and then annotated with the SwissProt, NR, NT, PFAM, KO, GO, KOG and KEGG databases. Moreover, 3982 differentially expressed unigenes (H vs HV) were determined, with 3583 upregulated and 399 downregulated genes. Among these differentially expressed unigenes, 207 unigenes were found using KEGG annotation in 16 immune-related signaling pathways, such as Toll-like receptor (TLR), NOD-like receptor (NLR), and RIG-I-like receptor (RLR) signaling pathways. Finally, we selected 11 full-length TLRs and classified them into 3 groups, namely, one V-TLR, four Ls-TLR and six sP-TLR; furthermore, we validated the increased expression patterns of the 11 TLRs in response to LPS injection. In summary, these results revealed multiple findings on potential immune-related genes, such as the differential expression analysis and annotation based on the A. sativa transcriptome in response to V. anguillarum stimulation, and explored the molecular and expression characterization of A. sativa TLRs, which provide new insights into the innate immune responses and defense mechanisms in shellfish.

A comparative synthesis of transcriptomic analyses reveals major differences between WSSV-susceptible Litopenaeus vannamei and WSSV-refractory Macrobrachium rosenbergii.

Since the 1990s White Spot Syndrome Virus (WSSV) has severely affected shrimp aquaculture worldwide causing a global pandemic of White Spot Disease (WSD) in penaeid culture. However, not all decapod species that can be infected by WSSV show the same susceptibility to the virus, thus raising interesting questions regarding the potential genetic traits that might confer resistance to WSSV. In order to shed light into the genetic markers of WSSV resistance, we employed a dual approach: i) we initially analysed the transcriptomes derived from the hepatopancreas of two species, the susceptible white shrimp Litopenaeus vannamei and the refractory fresh water prawn Macrobrachium rosenbergii, both infected with WSSV. We found a large number of differentially expressed genes (DEGs) belonging to the immune system (mostly anti-microbial peptides and haemolymph clotting components) that were generally up-regulated in M. rosenbergii and down-regulated in L. vannamei. Further, in both species we identified many up-regulated DEGs that were related to metabolism (suggesting a metabolic shift during the infection) and, interestingly, in L. vannamei only, we found several DEGs that were related to moult and suggested an inhibition of the moult cycle in this species following WSSV infection. ii) we then identified a limited number of genetic markers putatively linked with WSD tolerance by employing an ecological genomics approach in which we compared published reports with our own RNA-seq datasets for different decapod species infected with WSSV. Using this second comparative approach, we found nine candidate genes which are consistently down-regulated in susceptible species and up-regulated in refractory species and which have a role in immune response. Together our data offer novel insights into gene expression differences that can be found in susceptible and refractory decapod species infected with WSSV and provide a valuable resource towards our understanding of the potential genetic basis of tolerance to WSSV.

Photoperiod affects gamete production, and protein and lipid metabolism in male narrow-clawed Crayfish Pontastacus leptodactylus (Eschscholtz, 1823).

Understanding effects of photoperiod on the reproductive efficiency and physiological responses of Pontastacus leptodactylus is important for successful management of the crayfish hatcheries. Spermatozoal number, gonado-somatic index (GSI), hepatosomatic index (HSI), testicular index (TI), vas deferens index (VDI), and total protein, amino and fatty acid profiles of the hepatopancreas were evaluated in male narrow-clawed crayfish P. leptodactylus. Animals (30-70 g) were maintained utilizing five different photoperiodic regimens (3 L:21D, 6L:18D, 24 L:0D, 0L:24D, and natural photoperiod (9 L:15D)) for 5 weeks. Different photoperiods affected spermatozoal number, GSI, and total protein, amino acid and fatty acid profiles of the hepatopancreas (P < 0.05). The greatest spermatozoal number and GSI were recorded in darkness (P < 0.05). There was the least spermatozoal number (3.5 × 106 ± 0.5) and GSI (2 ± 0.1%) when imposing the 9 L and 24 L photoperiodic regimens, respectively. In addition, maintenance in constant light as compared with other lighting regimens resulted in a greater total protein (43.68 ± 4.83 mg/g), phenylalanine (7.23 ± 0.35%), and total single unsaturated fatty acids (ΣMUFA) (48.07 ± 2.30%), but lesser total polyunsaturated fatty acids (ΣPUFA) (23.36 ± 1.07%), serine (1.53 ± 0.02%), Σn-6 (11.24 ± 1.18%), 20:4 (n-6) (2.7 ± 0.14%), and 20:2 (0.67 ± 0.17%) contents in the hepatopancreas (P < 0.05). The results of the present study indicate total darkness increases the spermatozoal production and imposing longer dark periods improved the reproductive efficiency and physical conditions in male P. leptodactylus.

Transcriptional responses to starvation stress in the hepatopancreas of oriental river prawn Macrobrachium nipponense.

Various crustaceans are farmed using aquaculture, and food deprivation or fasting can occur due to changing of environmental or management strategies. However, the molecular mechanisms underlying responses to starvation in crustaceans remain unclear. To address this, 12 hepatopancreas transcriptomes were compared for oriental river prawn (Macrobrachium nipponense) from four fasting stages (0, 7, 14 and 21 d). Gene Ontology functional annotation and Kyoto Encyclopaedia of Genes and Genomes pathway enrichment analysis of differentially expressed genes were subsequently performed. During the early stages of starvation (0-7 d), drug metabolism via the cytochrome P450 pathway and metabolism of xenobiotics by the cytochrome P450 pathway were enriched, suggesting that they metabolised compounds generated under starvation stress. As starvation proceeded (7-14 d), the retinol (vitamin A) metabolism pathway was activated, based on three up-regulated genes (CYP3, ADH and UGT), along with the two p450 pathways. Meanwhile, vitamin A was gradually consumed. As acute starvation was reached (14-21 d), vitamin A deficiency decreased the mRNA expression levels of IGF-I that is involved in the mTOR signalling pathway, which ultimately affected the growth and development of M. nipponense. Our results implicate drug/xenobiotic metabolism by cytochrome P450s in adaptation to starvation stress. Furthermore, metabolic cascades (CYP and retinol pathways) and growth (mTOR signalling) pathways are clearly triggered in crustaceans during starvation. The findings expand our understanding of the genes associated with hepatopancreas functioning in M. nipponense, and the underlying molecular mechanisms that govern the responses of crustaceans to starvation stress.

Comparative transcriptome analysis reveals the different roles between hepatopancreas and intestine of Litopenaeus vannamei in immune response to aflatoxin B1 (AFB1) challenge.

Aflatoxin B1 (AFB1) is a mycotoxin mainly produced by Aspergillus flavus and Aspergillus parasiticus contaminating food, feed ingredients and products of animal origin. In mammals, this toxin causes widespread organ-specific damage; it is immunotoxicity and could promote hepatotoxicity, alter intestinal functions and so on. In this study, we conducted transcriptome and histomorphology analyses of hepatopancreas and intestinal in Litopenaeus vannamei (L. vannamei) challenged with AFB1. Totally 12,014 and 1387 differentially expression genes (DEGs) were identified in the hepatopancreas and intestine, respectively. In hepatopancreas, a total of 1995 DEGs were mainly annotated and grouped into 18 processes or pathways related to animal immune system. With respect to intestine, a total of 152 DEGs were mainly annotated to 7 processes or pathways related to animal immune system. Meanwhile, we determined the relative mRNA expression of several crucial representative immune genes including Toll, immune deficiency (IMD), prophenoloxidase (proPO), Rab and glutathione S-transferase (GST) in the hepatopancreas and intestines of shrimp at 3-, 6-, 12-, 18-, 24- and 30-d after challenged by AFB1. Exposure to AFB1 increased mortality, decrease weight gain rate, severely destroyed the histomorphology of hepatopancreas and intestine, and resulted in the damaged of immune system of shrimp. The present data reveals the different roles between hepatopancreas and intestine of L. vannamei in immune response to AFB1 challenge, and provides insight into the molecular basis of the relationship between hepatopancreas and intestinal immunity during either homeostasis or inflammation.

Cadmium-induced oxidative stress in Prussian carp (Carassius gibelio Bloch) hepatopancreas: ameliorating effect of melatonin.

The oxidative status of the hepatopancreas of Prussian carp females (Carassius gibelio) co-exposed to sublethal cadmium in water and melatonin was studied. The activities of antioxidant enzymes such as glutathione reductase (GR), glutathione peroxidase (GPx), and superoxide dismutase (SOD) as well as the concentration of reduced glutathione (GSH) were measured in homogenates of the hepatopancreas. Furthermore, concentrations of cadmium (Cd), zinc (Zn), copper (Cu), and iron (Fe) in the hepatopancreas were assayed. These females received melatonin implants and were exposed to 0.4 mg/L or 4.0 mg/L Cd in water for either a 13- or a 7-week period, followed by further 6 weeks of purification in clear water. Exposure to Cd influenced the increase in this metal concentration in fish hepatopancreas. In contrast, the fish exposed to cadmium with additional administration of melatonin had a lower accumulation of this metal. Exposure to Cd caused the increase in GSH content and the activity of GR, and a reduction in GPx activity, whereas the SOD activity varies depending on the exposure time on cadmium. In the hepatopancreas of fish treated with Cd alone, the content of Cu and Zn were increased and that of Fe was changed. After melatonin administration to Cd-exposed fish, a decrease in copper and zinc hepatopancreas content was noted. The present findings imply that melatonin co-treatment can effectively protect the fish against the toxic effects of cadmium on endogenous antioxidant status in hepatopancreas tissues and variations in metal concentration, such as Zn, Cu, and Fe.

Effects of Polyphenol Administration to European Farmed Sea Bass (Dicentrharcus labrax L.): Special Focus on Hepatopancreas Morphology.

BACKGROUND AND OBJECTIVE: Hepatopancreas is an accessory organ associated with the liver in some fish, even including sea bass (Dicentrharcus labrax L.). Hepatopancreas contains an exocrine portion but until now its function has poorly been investigated. METHODS: Here, European farmed sea bass have been treated with a feed enriched in polyphenols extracted from seeds of red grape (Nero di Troia cultivar) at two different doses (100 and 200 mg/kg, respectively) from day 273 to day 323. In fish samples, hepatopancreas area sizes have been measured to evaluate the effects of this dietary regimen on its morphology. RESULTS: Quite interestingly, in treated fish area sizes of hepatopancreas were higher than those detected in untreated fish. Two hundred mg dose of polyphenols was more effective than that of 100 mg/kg polyphenols. Finally, hepatic polyphenol concentration was diminished in fish receiving 100 mg dose polyphenols and normalized with 200 mg dose in comparison to untreated fish. This evidence suggests the utilization of polyphenols for liver function, even including hepatopancreas development. CONCLUSION: Our data suggest an expansion of hepatopancreas induced by polyphenol administration that is also associated with less mortality in farmed fish.

Transcriptome reveals involvement of immune defense, oxidative imbalance, and apoptosis in ammonia-stress response of the black tiger shrimp (Penaeus monodon).

Ammonia is a major aquatic environmental pollutant that negatively impacts shrimp health and commercial productivity. However, we currently do not fully understand the underlying molecular mechanisms of ammonia stress in shrimp. We therefore performed transcriptomic analysis of hepatopancreas from black tiger shrimp (Penaeus monodon) treated with ammonia-stress. We obtained 146,410,174 and 115,241,048 clean reads for the control and treatment groups, respectively. A total of 64,475 unigenes with an average length of 1275 bp and a N50 value of 2158 bp were assembled. A comparative transcriptome analysis identified 3462 differentially expressed genes, 177 of which are highly homologous with known proteins in aquatic species. Most of these genes showing the expression changes were related to immune function. Some significantly down-regulated genes are involved in purine metabolism and other metabolic pathways, which suggests that purineolytic capacity is an ammonia detoxification process in P. monodon, and metabolic depression is a strategy to reduce shrimp exposure to ammonia. Additionally, ammonia stress altered the expression patterns of key apoptosis genes (Bcl-xL, PERK, caspase 7, and caspase 10), confirmed that ammonia-stress induce oxidative stress and eventually even apoptosis. We also found evidence for the involvement of antioxidant defense in response to oxidative imbalance, given the regulation of peroxiredoxin 1, SOD, and CAT under ammonia stress. In conclusion, our study clarifies shrimp defensive response to ammonia toxicity and should benefit efforts to breed more ammonia-tolerant varieties.

D1 dopamine receptor is involved in shell formation in larvae of Pacific oyster Crassostrea gigas.

Dopamine (DA), a significant member of catecholamines, is reported to induce biomineralization of calcium carbonate vaterite microspheres via dopamine receptor (DR) in bivalves, implying the modulation of dopaminergic system on shell formation during larval development. In this research, a homologue of D1 type DR (CgD1DR-1) was identified from oyster Crassostrea gigas, whose full length cDNA was 1197 bp. It was widely expressed in various tissues of C. gigas, with the significantly higher levels in hepatopancreas, mantle, muscle and gill. During developmental stages, the mRNA transcripts of CgD1DR-1 in D-shape larvae were obviously higher (p < 0.05) than those in trochophore and umbo larvae, and CO2 exposure could inhibit the synthesis of DA and mRNA expression of CgD1DR-1. After cell transfection and DA treatment, intracellular cAMP in cells with the expression of CgD1DR-1 increased significantly (p < 0.05). Furthermore, the incubation with SCH 23390 for the blockage of CgD1DR-1 significantly restrained the expressions of six shell formation-related genes including CgTyrosinase-1, CgTyrosinase-3, CgChitinaseLP, CgAMC, CgBMP and CgBMPR in trochophore and D-shape larvae. These results jointly suggested that DA together with its receptor CgD1DR-1 might be involved in shell formation during oyster larval development from trochophore to D-shape larvae, and CO2-induced ocean acidification (OA) might influence marine bivalves by inhibiting the DA-D1DR pathway to prohibit their shell formation.

The comprehensive expression analysis of the G protein-coupled receptor from Penaeus monodon indicating it participates in innate immunity and anti-ammonia nitrogen stress.

The G protein-coupled receptors (GPCRs) composed a superfamily that played an important role in physiological processes of crustaceans, with multiple functions such as growth and development, acting as a defense against stimulations from external factors. In this paper, one kind of GPCRs were identified from Penaeus monodon, called PmGPCR, included an open reading frame (ORF) of 1113 bp. Bioinformatic analysis showed that PmGPCR protein had the typical structure of seven transmembrane domains (7TM), especially the special Asp-Arg-Try motif (DRY motif) between the third transmembrane structures (TM3) and the second intracellular loops (IL-2) which can prove that PmGPCR belongs to the rhodopsin-like family. The analyses of phylogenetic tree indicated that the amino acid sequence of PmGPCR should be merged into Procambarus clarkiic with high identity (98%). Quantitative real-time PCR (q RT-PCR) revealed that PmGPCR mRNA was highly expressed in hepatopancreas, abdominal ganglia and lymph, in which it was significantly higher than that of other tissues (P < 0.05). In addition, the expression of PmGPCR was analyzed during three days post-stimulation with the gram-positive/negative bacteria, the mRNA expression level increased after challenged with gram - positive bacteria in hepatopancreas, lymph and intestines. During the development stages, PmGPCR showed significantly higher expression in nauplius, zoea III, mysis III and post larvae stages than that in other development stages. Meanwhile, the highest transcripts expression of PmGPCR in abdominal ganglia, hepatopancreas, lymph and intestines respectively appeared at D0, D1, D2 and D3/D4 stages of molting. High or low concentration of ammonia nitrogen up-regulated the expression level of PmGPCR at the initial stage in hepatopancreas and gill, and then down-regulated at 48 h. These results indicated PmGPCR may mediate the pathways that involved in growth and development process, survival in the adversity, in addition, provided the useful data to research GPCR-mediated physiological and biological process and explain the mechanisms to defense pathogens and anti-stress in shrimp.

Lipopolysaccharide- and ß-1,3-glucan-binding protein from Litopenaeus vannamei: Purification, cloning and contribution in shrimp defense immunity via phenoloxidase activation.

Lipopolysaccharide- and ß-1,3-glucan-binding protein (LGBP) existed in diversity of invertebrates including shrimp plays a crucial role in an innate immunity via mediating the recognition of invading pathogens. In this study, LGBP was cloned and characterized from the hepatopancreas of Litopenaeus vannamei, named as LvLGBP. Its full-length cDNA of 1282 bp contained an open reading frame (1101 bp) encoding a peptide of 367 amino acids. The LGBP primary structure contained a glycosyl hydrolase domain, two integrin binding motifs, two kinase C phosphorylation sites, and two polysaccharide recognition motifs which were identified as a polysaccharide binding motif and a ß-1,3-glucan recognition motif. The LvLGBP transcripts were expressed mainly in the hepatopancreas. Upon challenge with Vibrio parahaemolyticus or white spot syndrome virus (WSSV), the LvLGBP mRNA expression was significantly up-regulated to reach a maximum at 48 h post injection. Its expression was also induced by lipopolysaccharide (LPS) or ß-1,3-glucan stimulation. RNAi-based silencing resulted in the critical suppression of LvLGBP expression. Knockdown of LvLGBP gene with co-inoculation by V. parahaemolyticus or WSSV led to increase in the cumulative mortality and reduce in the median lethal time. Native LGBP was detected only in the hepatopancreas as verified by Western blotting. Purified LGBP from the hepatopancreas exhibited the agglutinating and binding activity towards Gram-negative bacterium V. parahaemolyticus with calcium-dependence. Its agglutinating activity was dominantly inhibited by LPS with higher potential than ß-1,3-glucan. Purified LvLGBP could significantly activate the hemocyte phenoloxidase activity in the presence of LPS (12.9 folds), while slight activation was detected with ß-1,3-glucan (2.0 folds). It could enhance the encapsulation by hemocytes but did not have antibacterial activity. These results provided evidence that LvLGBP might act as a pathogenic recognition protein to activate shrimp immune defense against invading pathogens via the agglutination, binding and enhancing encapsulation and phenoloxidase activity of the hemocytes.

A single-domain rhodanese homologue MnRDH1 helps to maintain redox balance in Macrobrachium nipponense.

Rhodaneses are known to catalyze in vitro the transfer of a sulfane sulfur atom from thiosulfate to cyanide with concomitant formation of thiocyanate, however, their biological functions remain speculative despite the main role is considered as detoxifying cyanide especially in animal livers. In this study, we characterized a single-domain rhodanese homologue, MnRDH1, from Macrobrachium nipponense. We found MnRDH1 with the highest expression in hemocytes. Upon Aeromonas hydrophila challenge, expression of MnRDH1 was up-regulated in various tissues, including hepatopancreas, gill, intestine and hemocytes. RNAi knockdown of MnRDH1 led to rapid increases of malondialdehyde content, which reveals that MnRDH1 deficiency causes oxidative stress. The expression of MnRDH1 in hepatopancreas was significantly increased in response to the doxorubicin-induced oxidative stress, indicating the gene is oxidative stress inducible. We transformed E. coli with MnRDH1 and the mutant MnRDH1C75A, and found significant rhodanese activity of the recombinant protein of MnRDH1 in vitro, but detected no enzyme activity of the mutant MnRDH1C75A. When under the oxidative insult by H2O2, the MnRDH1 transformed E. coli had significantly enhanced survival rates compared to those bacteria transformed with MnRDH1C75A. In conclusion, our study demonstrates that rhodanese in M. nipponense confers oxidative stress tolerance, and thus renders an evidence for the notion that rhodanese family genes act a critical role in antioxidant defenses.

Scallop genome reveals molecular adaptations to semi-sessile life and neurotoxins.

Bivalve molluscs are descendants of an early-Cambrian lineage superbly adapted to benthic filter feeding. Adaptations in form and behavior are well recognized, but the underlying molecular mechanisms are largely unknown. Here, we investigate the genome, various transcriptomes, and proteomes of the scallop Chlamys farreri, a semi-sessile bivalve with well-developed adductor muscle, sophisticated eyes, and remarkable neurotoxin resistance. The scallop's large striated muscle is energy-dynamic but not fully differentiated from smooth muscle. Its eyes are supported by highly diverse, intronless opsins expanded by retroposition for broadened spectral sensitivity. Rapid byssal secretion is enabled by a specialized foot and multiple proteins including expanded tyrosinases. The scallop uses hepatopancreas to accumulate neurotoxins and kidney to transform to high-toxicity forms through expanded sulfotransferases, probably as deterrence against predation, while it achieves neurotoxin resistance through point mutations in sodium channels. These findings suggest that expansion and mutation of those genes may have profound effects on scallop's phenotype and adaptation.

The impact of seismic air gun exposure on the haemolymph physiology and nutritional condition of spiny lobster, Jasus edwardsii.

There is a critical knowledge gap regarding the impacts of seismic air gun signals on the physiology of adult crustaceans. We conducted four controlled field experiments to examine the impact of seismic acoustic signals on spiny lobster, Jasus edwardsii. Seismic air gun exposure suppressed total haemocyte count (THC) for up to 120days post-exposure, suggesting a chronic negative impact of immune competency. THC levels after 365days post-exposure, were elevated two fold, potentially indicating an immune response to infection. Haemolymph refractive index was reduced after 120days post exposure in one experiment, suggesting a chronic impairment of nutritional condition. There was no effect of air gun exposure on 24 haemolymph biochemical parameters, hepatopancreas index or survival. Collectively these results indicate that the biochemical haematological homeostasis of J. edwardsii is reasonably resilient to seismic acoustic signals, however, air gun exposure may negatively influence the lobster's nutritional condition and immunological capacity.

The versatile functions of LRR-only proteins in mollusk Chlamys farreri.

Leucine-rich repeat (LRR)-only proteins are involved in the innate immune responses as they mediate protein-ligand interactions. In the present study, three novel LRR-only proteins, CfLRRop-4, CfLRRop-5 and CfLRRop-6, were identified and characterized from Zhikong scallop Chlamys farreri. They all contained LRR motifs with consensus signature sequences of LxxLxLxxNxL or LxxLxLxxCxxL. All the mRNA transcripts of three CfLRRops were high abundant in hepatopancreas, gills and gonads, and their mRNA transcripts in hemocytes could respond to the stimulations of different microbes, including Vibrio anguillarum, Micrococcus luteus and Pichia pastoris. These three CfLRRops exhibited similar ligand binding and recognition characteristics as Toll-like receptors (TLRs) and NOD-like receptors (NLRs). The immune effectors, including tumor necrosis factor α, superoxide dismutase, catalase and lysozyme, varied significantly after the scallops were stimulated by recombinant LRR-only proteins. All these results indicated that LRR-only proteins are functionally differentiated and exhibit different immunomodulation activities on various downstream immune effectors.

Transcriptome, antioxidant enzyme activity and histopathology analysis of hepatopancreas from the white shrimp Litopenaeus vannamei fed with aflatoxin B1(AFB1).

Aflatoxin produced by Aspergillus flavus or Aspergillus parasiticus fungi during grain and feed processing and storage. Aflatoxins cause severe health problems reducing the yield and profitability of shrimp cultures. We sought to understand the interaction between shrimp immunity and aflatoxin B1 (AFB1), analyzing transcriptome expression, antioxidant enzyme activity, and histological features of the hepatopancreas of shrimp fed with AFB1. From over 4 million high-quality reads, de novo unigene assembly produced 103,644 fully annotated genes. A total of 1024 genes were differentially expressed in shrimp fed with AFB1, being involved in functions, such as peroxidase metabolism, signal transduction, transcriptional control, apoptosis, proteolysis, endocytosis, and cell adhesion and cell junction. Upon AFB1 challenge, there were severe histological alterations in shrimp hepatopancreas. AFB1 challenge increased the activity of several antioxidant enzymes. Our data contribute to improve the current understanding of host-AFB1 interaction, providing an abundant source for identification of novel genes.