Crab Hepatopancreas Research Articles

The hepatopancreas microbiome of velvet crab, Necora puber.

Crustaceans are a valuable resource globally, both ecologically and economically, and investigations into their health are becoming increasingly important as exploitation rises. The microbiome plays a crucial role in crustacean immunity, and understanding its composition and structure can provide insights into the health of an organism and its interactions with various factors. In this study, we investigated the hepatopancreas microbiome of the velvet swimming crab, Necora puber, and compared its composition and structure with several study factors, including two different sampling points and infection with a paramyxid parasite, Paramarteilia canceri. To our knowledge, we provide the first description of a velvet crab microbiome, highlighting the dominance of a single microorganism, Candidatus hepatoplasma. We identified variations in microbiome composition between sampling points and discussed the possible processes affecting microbiome assembly. We also outline a core microbiome for the velvet crab hepatopancreas, consisting of 12 core phyla. Our study adds to the growing literature on crustacean microbiomes and provides a baseline for future investigations into the velvet crab microbiome and the health of this crustacean species.

Multiple Biomarker Responses in Aegla castro Exposed to Copper: A Laboratory Approach.

Although some biomarkers have already been determined in aeglids collected in the field, data from laboratory exposures are scarce. To our knowledge, no studies have investigated oxidative stress biomarkers in aeglids exposed to metals in the laboratory, or performed hemocyte counts and the comet assay using gill and hepatopancreas of aeglids. Thus, we investigated the effects of acute Cu exposure on intermolt males of Aegla castro, collected from a reference stream, acclimated for 6days in the laboratory, and then exposed to 11μgL-1 of dissolved Cu (Cu 11) or only to water (CTR), for 24h. Gill and hepatopancreas samples were used to determine Cu accumulation, DNA damage, and metallothionein content (MT), while hemolymph samples were used to determine Cu accumulation, DNA damage, and hemocyte counts. Muscle samples were used to determine Cu accumulation and acetylcholinesterase activity (AChE). Non-protein thiol content (NPSH), catalase (CAT), glutathione S-transferase activities (GST), lipoperoxidation (LPO), and protein carbonylation content (PCC) were measured only in the hepatopancreas. Aegla castro exposed to Cu accumulated this metal in gills and activated detoxification mechanisms, through increased MT content in the gill, and showed an immune response, evidenced by an increase in hyaline hemocytes. Therefore, gill and hemocytes appear to have a protective role in preventing the transport and bioavailability of Cu through the body. On the other hand, we observed a decrease in MT content in the hepatopancreas of crabs exposed to Cu, suggesting the excretion of MT in association with Cu bound to the sulfhydryl groups of this protein.

Effects of Soybean Isoflavones on the Growth Performance and Lipid Metabolism of the Juvenile Chinese Mitten Crab Eriocheir sinensis

In order to study the effects of soybean isoflavones on the growth performance and lipid metabolism of juvenile Chinese mitten crabs, six experimental diets were formulated by gradient supplementation with 0%, 0.004% and 0.008% soybean isoflavones at different dietary lipid levels (10% and 15%). The groups were named as follows: NF-0 group (10% fat and 0% SIFs), NF-0.004 group (10% fat and 0.004% SIFs), NF-0.008 group (10% fat and 0.008% SIFs), HF-0 group (15% fat and 0% SIFs), HF-0.004 group (15% fat and 0.004% SIFs) and HF-0.008 group (15% fat and 0.008% SIFs). All crabs with an initial weight of 0.4 ± 0.03 g were fed for 8 weeks. The results showed that dietary supplementation with 0.004% or 0.008% SIFs significantly increased the weight gain and specific growth rate of crabs. Diets supplemented with 0.004% or 0.008% SIFs significantly reduced the content of non-esterified free fatty acids and triglycerides in the hepatopancreas of crabs at the 10% dietary lipid level. Dietary SIFs significantly decreased the relative mRNA expressions of elongase of very-long-chain fatty acids 6 (elovl6), triglyceride lipase (tgl), sterol regulatory element-binding protein 1 (srebp-1), carnitine palmitoyltransferase-1a (cpt-1a), fatty acid transporter protein 4 (fatp4), carnitine palmitoyltransferase-2 (cpt-2), Δ9 fatty acyl desaturase (Δ9 fad), carnitine palmitoyltransferase-1b (cpt-1b), fatty acid-binding protein 10 (fabp10) and microsomal triglyceride transfer protein (mttp) in the hepatopancreas of crabs. At the 15% dietary lipid level, 0.008% SIFs significantly increased the relative mRNA expressions of fatty acid-binding protein 3 (fabp3), carnitine acetyltransferase (caat), fatp4, fabp10, tgl, cpt-1a, cpt-1b and cpt-2 and significantly down-regulated the relative mRNA expressions of Δ9 fad and srebp-1. In conclusion, SIFs can improve the growth and utilization of a high-fat diet by inhibiting genes related to lipid synthesis and promoting lipid decomposition in juvenile Chinese mitten crabs.

Genome sequencing analysis and validation of infestation-related functional genes of Vibrio parahaemolyticus LG2206 isolated from the hepatopancreas of diseased mud crab (Scylla paramamosain) in South China

Vibrio parahaemolyticus (V. parahaemolyticus) is a major bacterial pathogen found in brackish environments, leading to disease outbreaks and great economic losses in the mud crab industry. This study investigated the molecular mechanism of V. parahaemolyticus infecting mud crabs through genome sequencing analysis, survival experiments, and the expression patterns of related functional genes. A strain of V. parahaemolyticus with high pathogenicity and lethality was isolated from diseased mud crab in South China. The genome sequencing results showed that the genome size of V. parahaemolyticus was a circular chromosome of 3,357,271 bp, with a GC content of 45 %, containing 2985 protein-coding genes, denoted as V. parahaemolyticus LG2206. Genome analysis data revealed that a total of 113 adherence coding genes were obtained, including 120 virulence factor coding genes, 37 type III secretion system (T3SS) coding genes, and 277 sequences of T3SS effectors. Survival experiments showed that the mortality was 20 % within 96 h in the 1 × 104 CFU/mL infection group, 90 % in the 3.2 × 105 CFU/mL treatment group, and 100 % in the 1 × 106 CFU/mL treatment group. The LD50 of V. parahaemolyticus LG2206 was determined as 4.6 × 104 CFU/mL. Six genes of znuA and fliD (flagellin encoding genes), yscE and yscR (T3SS encoding genes), and nfuA and htpX (virulence factor encoding genes) were selected and validated by quantitative real-time PCR analysis after infection with 4.6 × 104 CFU/mL of V. parahaemolyticus LG2206 for 96 h. The expression of the six genes exhibited a significant up-regulation trend at all tested time points. The results indicated that the infestation-related genes screened in the experiment play important roles in the infestation process. This study provides timely and effective information to further analyze the molecular mechanism of V. parahaemolyticus infection and develop comprehensive measures for disease prevention and control.

Morphology, processing attributes, fatty acid, and amino acid composition in cooked leg meat and raw hepatopancreas of juvenile male red king crab (Paralithodes camtschaticus) after 12 months of live holding

This study investigated how diet composition (DC) (i.e., raw shrimp or dry feed alone and combinations thereof) affected the morphology, processing attributes, fatty acid (FA)- and amino acid (AA) composition in cooked leg meat and raw hepatopancreas of juvenile red king crabs (RKCs). After 12 months, the crab weight nearly doubled, and the average mortality was 10%. The DC influenced the attributes of the cooked leg meat and the raw hepatopancreas. In addition, crumbling the dry feed led to reduced nutritive conditions, especially in the 80 and 100% dry feeding groups. In the leg meat, the main FA components were PUFA, MUFA, and SFA in descending order, while for the raw hepatopancreas, the corresponding order was MUFA, PUFA, and SFA. Minor AA variations across the groups were observed in the cooked leg meat and raw hepatopancreas. A PCA revealed a grouping of selected morphological-, processing attributes, and FAs according to the 20 and 100% dry feed groups. This study did not explore the specific feed intake. Hence, whether the results reflect the DC, a lower feed intake due to the crumbling, or a combination is unknown. Overall, the results show positive prospects for live holding of juvenile RKCs.

Rare Earth Element Accumulation in Fiddler Crabs (Minuca rapax) from the Rio Doce Tropical Estuary Strongly Affected by Mine Tailings Following the Fundão Disaster.

A mining tailing dam rupture in Brazil in November 2015 released millions of tons of mining waste into the Rio Doce ecosystem, leading to long-term aquatic ecosystem impacts. Although multiple lines of evidence indicate tailings associations with potentially toxic elements in estuarine sediments and biological impact and bioaccumulation pathways in fishes, the extent of contamination in base benthic species is still largely unknown. Moreover, Rare Earth Elements (REE) have not received any attention in this regard. This study assessed REE in fiddler crabs (Minuca rapax) sampled from the Rio Doce estuary in 2017, nearly 2years after the disaster. The ΣREE in crab hepatopancreas and muscle were high (327.83mgkg-1 w.w. and 33.84mgkg-1 w.w., respectively, compared to other assessments in crabs, indicating a preference for REE bioaccumulation in the hepatopancreas compared to muscle. Neodimium, La, and Ce were detected at the highest concentrations. The REE from the Rio Doce Basin were, thus, transported and deposited in the estuary with the mine tailings slurry, leading to bioaccumulation in crabs. This may lead to trophic effects and other ecological impacts not readily measured by typical impact assessment studies, revealing an invisible and not typically acknowledged damage to the Rio Doce estuary.

Toxicity, Oxidative Stress, and Tissue Distribution of Butachlor in the Juvenile Chinese Mitten Crab (Eriocheir sinensis)

The Chinese mitten crab (Eriocheir sinensis) is one of the most commercially important crustacean species in China. The aim of this study was to characterize the toxic effects of butachlor (an herbicide of the acetanilide class) on juvenile E. sinensis crabs. The lethal effects and the acute toxicity of butachlor on juvenile E. sinensis specimens were assessed through a semi-static in vitro experiment. We determined the activities of superoxide dismutase (SOD) and catalase (CAT) as well as the levels of glutathione (GSH) and malondialdehyde (MDA) in the gills and the hepatopancreas of the juvenile crabs, at different time points over a 14-day short-term exposure to butachlor. Moreover, we measured the residual levels of butachlor in three different tissues (gills, hepatopancreas, and muscles) of the juvenile crabs over a longer period. Our findings revealed that butachlor is highly toxic for juvenile E. sinensis crabs. In fact, the median lethal concentration (LC50) values of butachlor at 24, 48, 72, and 96 h were found to be 4.22, 1.84, 0.34, and 0.14 mg/L, respectively, while the safe concentration was 0.014 mg/L. The antioxidant defense ability of the juvenile E. sinensis crabs against butachlor was induced after exposure to the herbicide at a concentration of 0.01 mg/L. After 14 days of exposure to butachlor at 0.04 and 0.16 mg/L, both SOD and CAT were found to be significantly inhibited (p < 0.05), the GSH levels were found to be significantly decreased (p < 0.05) and the MDA levels were identified as significantly increased (p < 0.05). Moreover, after 14 days of exposure to butachlor at 0.16 mg/L, the activities of SOD and CAT as well as the content of GSH in the hepatopancreas were found to be significantly decreased (p < 0.05). Our results revealed that a high concentration of butachlor was capable of inducing oxidative stress and damage in juvenile E. sinensis crabs. The maximal residual value of butachlor was obtained in the gills, with a content of 4.56 μg/kg. Butachlor was not detected after 24 days in the aforementioned three tissues of the juvenile crabs, thereby indicating that it was effectively metabolized.

The involvement of VEGF and VEGFR in bacterial recognition and regulation of antimicrobial peptides in Eriocheir sinensis

Vascular endothelial growth factor (VEGF) and VEGF reporter (VEGFR) are essential molecules in VEGF signalling pathway. Although the functions of VEGF and VEGFR have been well reported in vertebrates, their functions are still poorly understood in invertebrates. In this study, the open reading frame sequences of EsVEGF1 and EsVEGFR4 were cloned from Eriocheir sinensis, and their corresponding proteins shared typical structure characteristics with their counterparts in other species. EsVEGF1 were predominantly expressed in hepatopancreas and muscle while EsVEGFR4 mainly expressed in hemocytes and intestine. The expression levels of EsVEGF1 in hemocytes were rapidly induced by Staphylococcus aureus and Vibrio parahaemolyticus, and it also increased rapidly in hepatopancreas after being challenged with V. parahaemolyticus. The expression levels of EsVEGFR4 only increased in hepatopancreas of crabs injected with S. aureus. The extracellular immunoglobulin domain of EsVEGFR4 could bind with Gram-negative and Gram-positive bacteria as well as lipopolysaccharide and peptidoglycan. EsVEGF1 could act as the ligand for EsVEGFR4 and Toll-like receptor and regulate the expression of crustins and lysozyme with a tissue-specific manner, while have no regulatory function on that of anti-lipopolysaccharide factors. This study will provide new insights into the immune defense mechanisms mediated by VEGF and VEGFR in crustaceans.

Histomorphological changes in gills and hepatopancreas of crabs: an integrative review

Crustaceans are a biological model of ecotoxicology and consequently are widely used to assess the impact of xenobiotics. The toxicity of xenobiotics starts in the interaction of biomolecules and can even cause changes in an entire ecosystem. This paper aims to compile the histomorphological changes caused by xenobiotics in the gills and hepatopancreas of crabs through an integrative review. The literature search was done using PubMed with keywords in English and the filters "full text" and "publications from 2001-21". A total of 299 studies were found and 35 of them were selected based on the title and abstract. Later, 17 were included in the study. There were 18 categories of histomorphological changes in the gills and 22 in the hepatopancreas. We noticed that there is no consensus on the terminology used for histomorphological changes in this group. Furthermore, it was observed that the quality of the histological slides was quite diverse, making the identification and comparison of changes in the images problematic. The aforementioned considerations justify the need for this study to address a gap and encourage future research to develop a guide of histomorphological changes in crabs and its use as a tool for environmental biomonitoring.

Evaluation of spray-dried blood meal for application in commercial-like feed for juvenile swimming crab (Portunus trituberculatus)

The objective of the present study was to evaluate the effects of replacing fish meal (FM) with spray-dried blood meal (SDBM) on growth performance, antioxidant capacity, digestive enzyme activity, tissue Fe content, gene expression related to inflammation, and the TOR pathway in juvenile swimming crab (Portunus trituberculatus). Four isonitrogenous (47.0% protein) and isolipidic (9.0% lipid) diets were formulated to contain different levels of SDBM, with FM replaced by SDBM at 0, 10%, 20%, and 30%, respectively. The results showed that crabs fed diet SDBM30 exhibited the lowest survival among all treatments, and crabs fed the SDBM20 diet had the highest final weight, percent weight gain, specific growth rate and feed efficiency among all treatments. In addition, the protein content of the crab hepatopancreas decreased significantly and the lipid content increased significantly as SDBM replaced FM in the diets. Compared to other diets, crabs fed the SDBM30 diet had the lowest activities of antioxidant enzymes and the highest concentration of malondialdehyde in the hepatopancreas and hemolymph. The Fe contents in hepatopancreas and gill increased significantly, and the color of the hepatopancreas got darker as replacement of FM with SDBM increased from 0% to 30%. The expression of genes related to TOR (tor, akt, s6, and s6k1) and antioxidant (gpx) pathways in the hepatopancreas were down-regulated significantly with increased replacement of dietary FM with SDBM. In contrast, expression levels of genes related to protein translation (4ebp1, eif4e1a, eif4e2, and eif4e3) and inflammation pathways (myd88, traf6, relish, and irak4) were up-regulated significantly in crabs fed diets with SDBM supplementation. In summary, replacing FM with less than 20% of SDBM can promote the growth, but can darken the hepatopancreas, negatively affect antioxidant capacity, and induce an inflammatory response.

Changes of nutrient composition in the ovaries and hepatopancreas of mud crab Scylla paramamosain broodstock and their offspring performance at different salinities

The mud crab Scylla paramamosain is a major marine crab species for aquaculture in the southern coastal regions of China. This study investigated the differences in the quality of low-salt cultured and wild mud crabs and the the salinity tolerance and growth performance of their offspring. Ovarian development and fatty acid and amino acid compositions in the hepatopancreas and ovaries of mature low-salt and wild mud crabs were compared. The gonadosomatic index was significantly lower, but the hepatopancreatic index was significantly higher in the low-salt mud crab than in the wild mud crab. The contents of C18:1, C22:6n3 (DHA), DHA/EPA, and n-3/n-6 fatty acids in the ovaries and hepatopancreas of the low-salt mud crab were significantly higher than those of the wild mud crab. Except for proline in the hepatopancreas of the low-salt group, there were no significant differences in amino acids in the ovaries and hepatopancreas between the two groups. Although the survival rate of larval mud crabs in the low-salt mud crab was significantly higher than that in the wild mud crab when the salinity was 24‰, there was no significant difference in the juvenile survival between the two groups. However, the survival rate of larval and juvenile mud crabs in the low-salt group was significantly higher than in the wild group when the salinity was 5 ‰ and 3 ‰, respectively. The final body weight, average weight, weight gain, and specific weight gain rate of male and female offspring in the low-salt group were significantly higher than in the wild group. However, the weight gain and specific growth rate of male offspring in the low-salt group in September–October were significantly lower than those of male mud crabs in the wild group. This study indicates that the mud crab can be domesticated for culture and breeding at low salinity.

Evaluation of Collagenase Activity from Crab Hepatopancreas in Different Model Systems.

The effect of Kamchatka crab hepatopancreas containing three collagenolytic isoenzymes Collagenase KK and proteinases of Streptomyces lavendulae on metabolic activity and cell death were carried out on in vitro models. It was shown that changes in the protein structure under the influence of Collagenase KK occurred earlier than under the effect of bacterial proteinases. At the same time, activity of Collagenase KK was significantly higher than that of bacterial proteinases (p<0.01). Both preparations had a pronounced time- and dose-dependent effects on metabolic activity of cells. Collagenase KK had low cytotoxic effect, and cells mainly died by apoptosis. Thus, hepatopancreas collagenase has a high activity and proapoptotic effect on cells and can be used in low concentrations for enzymatic disaggregation of tissues.

Differential molecular responses of hemolymph and hepatopancreas of swimming crab, Portunus trituberculatus, infected with Ameson portunus (Microsporidia)

Ameson portunus (Microsporidia) has caused serious economic losses to the aquaculture industry of swimming crab, Portunus trituberculatus. The hemolymph and hepatopancreas are the main immune organs of P. trituberculatus, and the main sites of A. portunus infection. Elucidating the response characteristics of hemolymph and hepatopancreas to microsporidian infection facilitates the development of microsporidiosis prevention and control strategy. This study performed comparative transcriptomic analysis of hemolymph (PTX/PTXA) and hepatopancreas (PTG/PTGA) of P. trituberculatus uninfected and infected with A. portunus. The results showed that there were 223 and 1309 differentially expressed genes (DEGs) in PTX/PTXA and PTG/PTGA, respectively. The lysosome pathway was significantly enriched after the invasion of the hemolymph by A. portunus. Also, immune-related genes were all significantly up-regulated in the hemolymph and hepatopancreas, suggesting that the invasion by A. portunus may activate host immune responses. Unlike hemolymph, antioxidant and detoxification-related genes were also significantly up-regulated in the hepatopancreas. Moreover, metabolism-related genes were significantly down-regulated in the hepatopancreas, suggesting that energy synthesis, resistance to pathogens, and regulation of oxidative stress were suppressed in the hepatopancreas. Hemolymph and hepatopancreas have similarity and tissue specificity to microsporidian infection. The differential genes and pathways identified in this study can provide references for the prevention and control of microsporidiosis.

Effects of soy isoflavones on growth performance, antioxidant capacity, non-specific immunity and lipid metabolism of juvenile Chinese mitten crab, Eriocheir sinensis

Soy isoflavones are phytoestrogens that provide protection against some hormonal disorders and regulate several physiological functions in animals. This study investigates the effects of soy isoflavones on body composition, antioxidant activity, non-specific immunity, and lipid metabolism in juvenile Chinese mitten crabs, Eriocheir sinensis. A total of 960 juvenile crabs (1.09 ± 0.01 g) were randomly assigned to 24 tanks (300L), with 40 crabs in each tank in four replicates. The crabs were fed diets (43.5% protein and 7% lipid) with six levels of soy isoflavones (0, 8.8, 15.8, 33.8, 66.8, and 137.0 mg/kg) at 4% BW/day for 56 days. The final biomass and biomass gain of crabs supplemented with 15.8 and 33.8 mg/kg soy isoflavones were significantly higher than those in the control group. The total lipid content in the whole-body and hepatopancreas of the crabs fed 15.8 and 33.8 mg/kg soy isoflavones was significantly lower than in the control group. Compared with the control group, soy isoflavones significantly enhanced the activities of superoxide dismutase, glutathione peroxidase and total antioxidant capacity in the hepatopancreas by 40%, 57% and 79%, respectively, and significantly decreased malondialdehyde content by 24%. The high dietary soy isoflavones levels increased total protein and hemocyanin contents in hemolymph, and alkaline phosphatase activity was also significantly enhanced. The triglyceride contents in the hepatopancreas and hemolymph were significantly lower in the soy isoflavones-supplemented group. Dietary soy isoflavones may reduce lipid accumulation in the hepatopancreas by repressing genes related to lipid synthesis and promoting the expression of lipid oxidation and transport genes. The broken-line model analysis of biomass gain against dietary soy isoflavones levels shows that the optimal supplemental level of soy isoflavones for juvenile crabs is approximately 26.66 mg/kg. Thus, this study suggests that dietary soy isoflavones supplementation can improve growth performance and health and reduce lipid accumulation in the hepatopancreas of juvenile crabs.

Feeding Lycium barbarum polysaccharides (LBP) alleviates apoptotic, inflammatory hepatopancreas atrophy and injury in Chinese mitten crab (Eriocheir sinensis) poisoned by T-2 toxin

Chinese herbs and their purified components in aquafeeds have been proved effective to combat stress in aquatic animals to combat toxic environmental stress. Lycium barbarum poly-saccharides (LBP) is an active antioxidant, anti-inflammatory and antitoxic purified herbal agent. The objective of this paper was to evaluate the effect of 0.1–2.0% LBP on the hepatopancreas of Chinese mitten crab (Eriocheir sinensis) challenged with 2 mg/kg T-2 toxin orally for 5 weeks. The results showed that feeding LBP significantly restored the hepatopancreas index (HI), gonadsomatic index (GSI) reduced by T-2 toxin. Moreover, H&E sections indicated that LBP dose-dependently restored the disrupted microstructure of the hepatopancreas. In antioxidative capacity, significant increases in malondialdehyde (MDA) reduction and elevated glutathione (GSH) content, gluta-thione reductase (GPx) activity were seen in the 0.5% LBP group. In addition, reactive oxygen species (ROS) and apoptosis rate of hepatopancreas showed the anti-apoptotic effect of LBP doses, plus qPCR assay of 10 apoptosis-related genes to support them. The mRNA abundance of three pro-inflammatory genes was significantly reduced by LBP, corroborating its anti-inflammatory efficacy. In brief, feed supplementation with LBP alleviated the oxidative stress-apoptosis-inflammation induced by co-feeding T-2 toxin in E. sinensis, maintained the structural and functional integrity of the hepatopancreas, prevented degenerative atrophy.

Microcystin-LR-induced autophagy via miR-282–5p/PIK3R1 pathway in Eriocheir sinensis hepatopancreas

With the intensifying climate warming, blue-green algae blooms have become more frequent and severe, releasing environmental hazards such as microcystin that pose potential threats to human and animal health. Autophagy has been shown to play a crucial role in regulating immune responses induced by environmental hazards, enabling cells to adapt to stress and protect against damage. Although microcystin-LR (MC-LR) has been identified to affect autophagy in mammalian, its impact on aquatic animals has been poorly studied. To investigate the toxicological effects of MC-LR in aquatic ecosystems, we constructed a microRNA profile of acute MC-LR stress in the hepatopancreas of the Chinese mitten crab. Interestingly, we found the MC-LR exposure activated autophagy in the hepatopancreas based on the following evidence. Specifically, mRNA expression level of ATG7, Beclin1 and Gabarap was significantly up-regulated, autophagy regulatory pathways were significantly enriched, and numerous autolysosomes and autophagosomes were observed. Additionally, we found that miR-282–5p and its target gene PIK3R1 played important regulatory roles in autophagy by in vivo and in vitro experiments. Overexpression of miR-282–5p mimicked MC-LR-induced autophagy by inhibiting PIK3R1 expression, while miR-282–5p silencing inhibited autophagy by promoting PIK3R1 expression. Altogether, our findings suggest that MC-LR increases miR-282–5p, which then targets inhibition of PIK3R1 to stimulate autophagy. This study focused on the stress response regulatory mechanisms of juvenile crabs to toxic pollutants in water, offering a potential target for alleviating the toxicity of MC-LR. These findings lay a foundation for reducing the toxicity of MC-LR and environmental hazards in organisms.

Novel Antimicrobial Peptide from the Hepatopancreas of the Red King Crab.

Crustaceans have successfully adapted to survive in their natural habitat, rich in microorganisms, due to the presence of antimicrobial peptides (AMPs) in their organism. They achieve this adaptation despite lacking the highly specific adaptive immune system found in vertebrates. One valuable source of AMPs is the hepatopancreas, a waste product from crab fishery and its processing. Applying zymographic and spectrophotometric techniques, we discovered a small peptide (approximately 5 kDa) within a low molecular weight protein fraction extracted from the acetone powder of the red king crab hepatopancreas. This peptide hydrolyzes both M. lysodeikticus cell wall and M. lysodeikticus cell wall polysaccharide, while showing no activity against gelatin. The found peptide may be of interest for application in medicine, biotechnology, and the food industry, for example as a bio-preservative.

Microbiome and transcriptome analyses reveal the influence of calcined dolomite application on Eriocheir sinensis in a rice–crab co-culture system

Co-culture systems of rice and aquatic animals can contribute to the ecological intensification of agriculture by reducing nutrient loss and the need for N fertilizer application and by enhancing nutrient-use efficiency. However, the input of high-protein diets into paddy fields, to facilitate the growth of aquatic animals, has been found to increase N pollution and acidification of the soil. Although soil amendments have been widely used to ameliorate acidic soils, reduce N2O emissions, and improve agronomic production, the relationship between soil amendments and aquatic animal remains unclear. Therefore, this study investigated the effects of calcined dolomite (hereafter referred to as dolomite) as an acidic soil amendment and Ca–Mg supplement in rice–crab co-culture using Eriocheir sinensis crabs (Chinese mitten crabs). High-throughput sequencing was used to examine crab bacterial community composition and crab hepatopancreas biology. Although the water pH was significantly increased in the dolomite group, the number, composition, and diversity of bacteria identified in crab gut microbiome did not vary significantly between the dolomite and control groups. In the dolomite group, the probiotic agents Candidatus Hepatoplasma and Lactobacillus were highly abundant in the crab gut, and immune- and retinol metabolism-related genes were significantly upregulated in the crab hepatopancreas. Overall, dolomite application increased crab health and water pH. Dolomite is a low-cost amendment, with better stability, compared to other soil amendments, thus making it ideal for sustainable and clean rice–aquatic animal co-culture.

Starvation induces hepatopancreas atrophy in Chinese mitten crab (Eriocheir sinensis) by inhibiting angiogenesis

BackgroundThe hepatopancreas of crustaceans serves as a significant organ for both the synthesis and secretion of digestive enzymes, as well as energy storage. In the event of food shortage, the hepatopancreas can provide energy for survival. To investigate the potential regulatory mechanisms of the hepatopancreas in response to starvation in Eriocheir Sinensis, transcriptome analysis, histological study and qRT-PCR were performed.ResultsThe results showed that starvation caused a decrease in the hepatopancreas index of E. sinensis, which had certain effects on the tissue structure, metabolism and angiogenesis in the hepatopancreas. In addition, WGCNA and linear regression analysis showed that the genes significantly related to the hepatopancreas index were mainly enriched in the angiogenesis pathway, in which AKT signaling played an important role. Starvation may inhibit AKT signaling pathway by reducing the expression of TGFBI, HSP27, HHEX, and EsPVF1, thereby hindering angiogenesis, promoting apoptosis, and leading to hepatopancreas atrophy.ConclusionThese results indicate that AKT plays an important role in the angiogenesis pathway and apoptosis of the starvation induced hepatopancreas index reduction, which is beneficial to further understand the effect of starvation stress on hepatopancreas of Chinese mitten crab.

Effects of Ambient Ammonia‐Nitrogen Exposure on Uric Acid and Urea Metabolic Pathways and Tissue Distribution in the Swimming Crab Portunus trituberculatus

AbstractAmmonia‐nitrogen (ammonia‐N) is an important threat factor to the development of the crustacean breeding industry; however, information on nitrogen metabolism remains limited. In this study, effects of ammonia‐N on the metabolic pathways and tissue distribution of nitrogenous wastes were investigated in swimming crabs Portunus trituberculatus. The results showed that ammonia content in the hemolymph of crabs exposed to 1‐ and 5‐mg/L NH4Cl (ammonia‐N concentrations were 1.36 and 5.31 mg/L, respectively) significantly (P &lt; 0.05) increased with time. The expression of xanthine oxidase was significantly up‐regulated in gills and muscles but was significantly down‐regulated in the hepatopancreas of crabs exposed to 1‐ and 5‐mg/L NH4Cl after 6–12 h. The expression of uricase was significantly up‐regulated in gills and muscles at 3 h, whereas it was significantly down‐regulated in hepatopancreas during 6–12 h but up‐regulated again after 24 h. Moreover, the expression levels of carbamoyl phosphate synthetase III and arginase were significantly up‐regulated in gills and muscles but significantly down‐regulated in the hepatopancreas of crabs exposed to 5‐mg/L NH4Cl after 6–12 h. Furthermore, under 5‐mg/L NH4Cl stress, trace amounts of uric acid were detected, which significantly increased in hepatopancreas and hemolymph at 3 h, in muscles at 6–12 h, and in gills at 6–24 h. In addition, similar to hemolymph ammonia, urea was also significantly increased after NH4Cl exposure. Moreover, uric acid was mainly stored in muscles and urea was primarily synthesized in the hepatopancreas. This study provides a theoretical basis for further study on the nitrogen metabolism mechanism in crustaceans.