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

Effects of Astaxanthin on Ovarian Development of Largemouth Bass (Micropterus salmoides)

The purpose of the study was to investigate the effects of astaxanthin on ovarian development of largemouth bass (Micropterus salmoides) female. Five isonitrogenous and isolipidic feeds with varying levels of astaxanthin (0.8, 19, 41, 97, and 200 mg/kg) were grouped as AS0, AS20, AS40, AS100, and AS200, respectively. The results indicated that the gonadosomatic index (GSI) was significantly greater in the AS40 and AS100 than in AS0 and AS200 (p < 0.05). The AS40 and AS100 exhibited a dramatically lower hepatosomatic index (HSI) compared to the other groups (p < 0.05). The content of vitellogenin (VTG) was significantly increased in AS100 compared to the AS0, AS20, and AS200 (p < 0.05). Testosterone (T) levels were significantly lower in the AS200 compared to the other groups (p < 0.05). The AS40, AS100, and AS200 groups exhibited significantly greater follicle-stimulating hormone (FSH) levels than the AS0 and AS20 group (p < 0.05). The luteinizing hormone (LH) level was significantly higher in AS100 compared to the other groups (p < 0.05). The estradiol (E2) levels were significantly higher in AS40 compared to the AS0 and AS200 groups (p < 0.05). The total antioxidant capacity (T-AOC) was significantly higher in AS100 than the AS0 and AS20 groups (p < 0.05). The superoxide dismutase (SOD) activity was significantly higher in AS40 compared to the AS0 and AS200 groups (p < 0.05). The malondialdehyde (MDA) level was significantly decreased in AS40 than the other groups (p < 0.05). Transcriptomic analysis of ovarian tissue revealed that differentially expressed genes primarily involved in pathways such as "ovarian steroidogenesis," "steroid hormone biosynthesis," and "arachidonic acid metabolism." The expression of genes involved in ovarian steroidogenesis and arachidonic acid metabolism, such as cytochrome P450 family 2 subfamily J member (cyp2j), insulin-like growth factor 1 (igf1), phospholipase A2 group (pla2g), FSH receptor (fshr), and acute regulatory protein (star), was significantly upregulated in the AS40 group (p < 0.05). In summary, appropriate amount of astaxanthin supplementation in the diet enhance gonadal development, antioxidant capacity, and sex hormone levels, promote the expression of genes related to gonadal development, and consequently, enhance reproductive performance of largemouth bass.

Effects of dietary supplementation with medicinal plant mixtures and immunostimulants on the immune response, antioxidant capacity, and hepatopancreatic health of Chinese mitten crab (Eriocheir sinensis)

Introduction

This study aimed to evaluate the efficiency of tea polyphenols (TP) and medicinal plant mixtures (Astragalus membranaceus + Lonicera japonica, Rheum officinale Bail + Scutellaria baicalensis + Platycladus orientalis) combined with astaxanthin (AST), benzoic acid (BA), and yeast complex on the health status of Eriocheir sinensis.

Method

A total of 630 crabs (male crabs: 41.51 ± 1.63 g; female crabs: 47.27 ± 0.79 g) were randomly distributed into seven groups with three replicates (male: female, 1:1). These crabs were fed as follows for 8 weeks: basal diet (M1), M2 (M1 + 100 mg/kg TP), M3 (M1 + 2.0 g/kg A. membranaceus + 20 g/kg L. japonica), M4 (M1 + 2.5 g/kg R. officinale Bail + 1.5 g/kg S. baicalensis + 1.0 g/kg P. orientalis), and M5, M6, M7 (M2, M3 and M4 with 600 mg/kg AST +1.0 g/kg BA + 20 mg/kg yeast complex added, respectively).

Results and discussion

The results showed that the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), and lysosome (LZM) in the hemolymph were significantly increased in M5, M6, and M7 (P < 0.05), and the highest phagocytosis index (PI) and LZM activity were observed in M7 of female crabs. Moreover, the antioxidant indicators superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), and catalase (CAT) of hepatopancreas were also significantly improved in M5, M6, and M7 (P < 0.05), while the malondialdehyde (MDA) contents showed an opposite trend. Furthermore, a morphological examination also showed the improved histological structure of hepatopancreas in M7, especially as seen in the clear lumens, no vacuolation, and integrity of the basal membrane of the hepatopancreatic tubule. Taken together, these results suggested that 2.5 g/kg R. officinale Bail, 1.5 g/kg S. baicalensis, and 1.0 g/kg P. orientalis in combination with 600 mg/kg AST, 1.0 g/kg BA, and 20 mg/kg yeast complex could improve the non-specific immunity, antioxidant capacity, and hepatopancreatic health of E. sinensis.

Xanthophyllomyces dendrorhous Is a Safe Dietary Supplement with Potent Antioxidant Defense Enhancing Activity

Xanthophyllomyces dendrorhous (X. dendrorhous), previously known as Phaffia rhodozyma, is a red yeast that is widely recognized as a rich source of carotenoids, particularly astaxanthin, which exhibits potent antioxidant activity and other health-promoting functions. However, there is currently a lack of research on the safety of consuming X. dendrorhous. To address this, we conducted an acute toxicity study followed by a 90-day subchronic toxicity trial to evaluate the safety of X. dendrorhous and investigate its in vivo antioxidant activity. In the acute toxicity study, Sprague-Dawley rats were administered a maximum of 12 g/kg body weight of X. dendrorhous powder by gavage and survived without any adverse effects for 14 days. In the subsequent subchronic toxicity test, the rats were randomly divided into five groups, each with free access to their diet adulterated with 0% (control), 2.5% (low), 5% (middle), 10% (high), and 20% (extreme high) X. dendrorhous powder. The rats' behavior, body weight, and food intake were monitored during the 90-day experiment. At the end of the experiment, urine, blood, and organs were collected from the rats for biochemical testing. Additionally, the antioxidant activity in rat sera was evaluated. The results of the acute toxicity test demonstrated that the LD50 of X. dendrorhous was greater than 12 g/kg body weight, indicating that the substance was not toxic. Throughout the 90-day period of subchronic toxicity, the triglyceride levels of male rats fed with 10 and 20% X. dendrorhous increased to 1.54 ± 0.17 and 1.55 ± 0.25 mmol/L (P < 0.05), respectively. This may be attributed to the elevated fat content of the diet in the high-dose and extreme high-dose groups, which was 5.5 and 2.5% higher than that in the control, respectively. Additionally, the white pulp in the spleen exhibited an increase, and the number of white blood cells in the extreme high-dose group increased by 2.41 × 109/L (P < 0.05), which may contribute to enhanced immunity. Finally, the body weight, food intake, blood and urine indexes, and histopathological examination results of the organs of the rats did not demonstrate any regular toxic effects. With the adulteration of X. dendrorhous, the activity of GSH-Px in male rats increased by 16-36.32%. The activity of GSH-Px in female rats of the extreme high-dose group increased by 14.70% (P < 0.05). The free radical scavenging ability of ABTS in male rats in the two high-dose groups exhibited an increase of 6.5 and 11.41% (P < 0.05). In contrast, the MDA content of male rats in the extreme high-dose group demonstrated a reduction of 2.73 nmol/mL (P < 0.05). These findings indicate that X. dendrorhous has no toxic effects, can be taken in high doses, and has a beneficial antioxidant effect that may enhance the body's immunity.

NinaB and BCO Collaboratively Participate in the β-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 β, β-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 β-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 β-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 β-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 β-carotene content was observed in the hepatopancreas when EsNinaBl-mRNA was suppressed, which suggests that EsNinaBl plays an important role in carotenoid cleavage, specifically β-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.

Dietary Astaxanthin Can Promote the Growth and Motivate Lipid Metabolism by Improving Antioxidant Properties for Swimming Crab, Portunus trituberculatus

This study aimed to assess the influence of varying dietary levels of astaxanthin (AST) on the growth, antioxidant capacity and lipid metabolism of juvenile swimming crabs. Six diets were formulated to contain different AST levels, and the analyzed concentration of AST in experimental diets were 0, 24.2, 45.8, 72.4, 94.2 and 195.0 mg kg-1, respectively. Juvenile swimming crabs (initial weight 8.20 ± 0.01 g) were fed these experimental diets for 56 days. The findings indicated that the color of the live crab shells and the cooked crab shells gradually became red with the increase of dietary AST levels. Dietary 24.2 mg kg-1 astaxanthin significantly improved the growth performance of swimming crab. the lowest activities of glutathione (GSH), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and peroxidase (POD) were found in crabs fed without AST supplementation diet. Crabs fed diet without AST supplementation showed lower lipid content and the activity of fatty acid synthetase (FAS) in hepatopancreas than those fed diets with AST supplementation, however, lipid content in muscle and the activity of carnitine palmitoyl transferase (CPT) in hepatopancreas were not significantly affected by dietary AST levels. And it can be found in oil red O staining that dietary 24.2 and 45.8 mg kg-1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas. Crabs fed diet with 195.0 mg kg-1 AST exhibited lower expression of ampk, foxo, pi3k, akt and nadph in hepatopancreas than those fed the other diets, however, the expression of genes related to antioxidant such as cMn-sod, gsh-px, cat, trx and gst in hepatopancreas significantly down-regulated with the increase of dietary AST levels. In conclusion, dietary 24.2 and 45.8 mg kg-1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas and im-proved the antioxidant and immune capacity of hemolymph.

Recent progress in practical applications of a potential carotenoid astaxanthin in aquaculture industry: a review

Astaxanthin is the main natural C40 carotenoid used worldwide in the aquaculture industry. It normally occurs in red yeast Phaffia rhodozyma and green alga Haematococcus pluvialis and a variety of aquatic sea creatures, such as trout, salmon, and shrimp. Numerous biological functions reported its antioxidant and anti-inflammatory activities since astaxanthin possesses the highest oxygen radical absorbance capacity (ORAC) and is considered to be over 500 more times effective than vitamin E and other carotenoids such as lutein and lycopene. Thus, synthetic and natural sources of astaxanthin have a commanding influence on industry trends, causing a wave in the world nutraceutical market of the encapsulated product. In vitro and in vivo studies have associated astaxanthin's unique molecular features with various health benefits, including immunomodulatory, photoprotective, and antioxidant properties, providing its chemotherapeutic potential for improving stress tolerance, disease resistance, growth performance, survival, and improved egg quality in farmed fish and crustaceans without exhibiting any cytotoxic effects. Moreover, the most evident effect is the pigmentation merit, where astaxanthin is supplemented in formulated diets to ameliorate the variegation of aquatic species and eventually product quality. Hence, carotenoid astaxanthin could be used as a curative supplement for farmed fish, since it is regarded as an ecologically friendly functional feed additive in the aquaculture industry. In this review, the currently available scientific literature regarding the most significant benefits of astaxanthin is discussed, with a particular focus on potential mechanisms of action responsible for its biological activities.

Effects of dietary astaxanthin on growth performance, muscle composition, non-specific immunity, gene expression, and ammonia resistance of juvenile ivory shell (Babylonia areolate)

Astaxanthin is one of the important immunopotentators in aquaculture. However, little is known about the physiological changes and stress resistance effects of astaxanthin in marine gastropods. In this study, the effects of different astaxanthin concentrations (0, 25, 50, 75, and 100 mg/kg) on the growth, muscle composition, immune function, and resistance to ammonia stress in Babylonia areolata were investigated after three months of rearing. With the increase in astaxanthin content, the weight gain rate (WGR), specific growth rate (SGR), and survival rate (SR) of B. areolata showed an increasing trend. The 75-100 mg/kg group was significantly higher than the control group (0 mg/kg). There was no significant difference in the flesh shell ratio (FSR), viscerosomatic index (VSI), and soft tissue index (STI) of the experimental groups. Astaxanthin (75 mg/kg) significantly increased muscle crude protein content and increased hepatopancreas alkaline phosphatase (AKP), superoxide dismutase (SOD), and catalase (CAT) activity. Astaxanthin (75-100 mg/kg) significantly increased the total antioxidant capacity (T-AOC) and acid phosphatase (ACP) of the hepatopancreas and decreased the malondialdehyde (MDA) content of B. areolata. Astaxanthin significantly induced the expression levels of functional genes, such as SOD, Cu/ZnSOD, ferritin, ACP, and CYC in hepatopancreas and increased the survival rate of B. areolata under ammonia stress. The addition of 75-100 mg/kg astaxanthin to the feed improved the growth performance, muscle composition, immune function, and resistance to ammonia stress of B. areolata.

New insights into micro-algal astaxanthin's effect on deoxynivalenol-induced spleen lymphocytes pyroptosis in Cyprinus carpio: Involving mitophagy and mtROS-NF-κB-dependent NLRP3 inflammasome

Deoxynivalenol (DON) is one of the most common sources of fungal toxins in fish feed, posing a significant risk to the immune and reproductive systems of fish. Microalgal astaxanthin (MIA), a potent antioxidant derived from microalgae, confers multifarious advantages upon piscine organisms, notably encompassing its anti-inflammatory and antioxidant prowess. Herein, we investigated the potential of MIA in ameliorating the immunotoxicity of DON on carp (Cyprinus carpio L.) based on spleen lymphocytes treated with DON (1.5 ng/ml) and/or MIA (96 μM). Firstly, CCK8 results showed that DON resulted in excessive death of spleen lymphocytes. Secondly, spleen lymphocytes treated with DON had a higher proportion of pyroptosis, and the mRNA and protein levels of pyroptosis (NLRP3, IL-1β and ASC) in spleen lymphocytes were increased. Thirdly, the relative red fluorescence intensity of JC-1 and DCFH-DA showed decreased mitochondrial membrane potential and increased ROS in spleen lymphocytes treated with DON. Mitochondrial ATP, DNA and NADPH/NADP+ analysis revealed decreased mitochondrial ATP, DNA and NADPH/NADP+ levels in DON-treated lymphocytes, corroborating the association between DON exposure and elevated intracellular ATP, DNA and NADPH/NADP+ in lymphocytes. DON exposure resulted in the downregulation of mitophagy-related genes and proteins (PINK1, Parkin and LC3) in lymphocytes. Notably, these effects were counteracted by treatment with MIA. Furthermore, DON led to the elevated secretion of inflammatory factors (TNF-α, IL-4 and IFN-γ), thereby inducing immune dysfunction in spleen lymphocytes. Encouragingly, MIA treatment effectively mitigated the immunotoxic effects induced by DON, demonstrating its potential in ameliorating pyroptosis, mitochondrial dysfunction and mitophagy impairment via regulating the mtROS-NF-κB axis in lymphocytes. This study sheds light on safeguarding farmed fish against agrobiological threats posed by DON, highlighting the valuable applications of MIA in aquaculture.

Micro-algal astaxanthin ameliorates polystyrene microplastics-triggered necroptosis and inflammation by mediating mitochondrial Ca2+ homeostasis in carp's head kidney lymphocytes (Cyprinus carpio L.)

Polystyrene microplastics (PM) is a pressing global environmental concern, posing substantial risks to aquatic ecosystems. Microalgal astaxanthin (MA), a heme pigment, safeguards cells against oxidative damage induced by free radicals, which contributes to various health conditions, including aging, inflammation and chronic diseases. Herein, we investigated the potential of MA in ameliorating the immunotoxicity of PM on carp (Cyprinus carpio L.) based on head kidney lymphocytes treated with PM (250 μM) and/or MA (100 μM). Firstly, CCK8 results showed that PM resulted in excessive death of head kidney lymphocytes. Secondly, head kidney lymphocytes treated with PM had a higher proportion of necroptosis, and the levels of necroptosis-related genes in head kidney lymphocytes were increased. Thirdly, the relative red fluorescence intensity of JC-1 and MitoSox showed decreased mitochondrial membrane potential and increased mtROS in head kidney lymphocytes treated with PM. MitoTracker® Green FM fluorescence analysis revealed enhanced mitochondrial Ca2+ levels in PM-treated lymphocytes, corroborating the association between PM exposure and elevated intracellular Ca2+ dynamics. PM exposure resulted in upregulation of calcium homeostasis-related gene (Orail, CAMKIIδ and SLC8A1) in lymphocytes. Subsequent investigations revealed that PM exposure reduced miR-25-5p expression while increasing levels of MCU, MICU1, and MCUR1. Notably, these effects were counteracted by treatment with MA. Furthermore, PM led to the elevated secretion of inflammatory factors (IFN-γ, IL-1β, IL-2 and TNF-α), thereby inducing immune dysfunction in head kidney lymphocytes. Encouragingly, MA treatment effectively mitigated the immunotoxic effects induced by PM, demonstrating its potential in ameliorating necroptosis, mitochondrial dysfunction and immune impairment via regulating the miR-25-5p/MCU axis in lymphocytes. This study sheds light on safeguarding farmed fish against agrobiological threats posed by PM, highlighting the valuable applications of MA in aquaculture.

Antioxidant characteristics of hydrolysate from low-value sea cucumber: In vitro and in vivo activities of Caenorhabditis elegans

The antioxidant activity in vitro and in vivo of Actinopyga miliaris hydrolysate (AMH) was investigated. The proportion of oligopeptides with 150-1000 Da in AMH was 65.48%. The IC50 values of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), hydroxyl radical scavenging ability, and ferric ion reducing power of AMH were 0.37, 3.43, and 24.15 mg/mL, respectively. Compared with the control group, the body length of Caenorhabditis elegans fed with 8 mg/mL AMH extended from 632.08 μm to 1009.57 μm, and the swallowing frequency and head-swing frequency increased significantly. After being fed with AMH, the lifespan of C. elegans can be prolonged even under stress conditions, primarily due to superoxide dismutase activity, catalase activity, reduced glutathione content, and total antioxidant capacity in C. elegans increased, whereas reactive oxygen species level was reduced. The results showed that AMH had in vitro and in vivo antioxidant activity, which can alleviate oxidative damage and prolong life of C. elegans.

Micro-algal astaxanthin improves lambda-cyhalothrin-induced necroptosis and inflammatory responses via the ROS-mediated NF-κB signaling in lymphocytes of carp (Cyprinus carpio L.)

Lambda-cyhalothrin (LCY) is a widely used toxic pesticide that causes harmful effects on the immune organs of fish and aquatic species. Micro-algal astaxanthin (MAA), a heme pigment found in haematococcus pluvialis, has been shown to benefit antioxidants and immunity in aquaculture. To investigate how MAA protects carp lymphocytes from LCY-induced immunotoxicity, a model of fish lymphocytes treated with LCY and/or MAA was established. Lymphocytes from carp (Cyprinus carpio L.) were given LCY (80 μM) and/or MAA (50 μM) as a treatment for a period of 24 h. Firstly, LCY exposure resulted in excessive ROS and malondialdehyde production and reduces antioxidant enzymes (SOD and CAT), indicating a reduced capacity of the antioxidant system. Secondly, the results of flow cytometry and AO/EB labeling proved that lymphocytes treated with LCY have a larger ratio of necroptosis. In addition, LCY upregulated the levels of necroptosis-related regulatory factors (RIP1, RIP3 and MLKL) via the ROS-mediated NF-κB signaling pathway in lymphocytes. Thirdly, LCY treatment caused increased secretion of inflammatory genes (IL-6, INF-γ, IL-4, IL-1β and TNF-α), leading to immune dysfunction in lymphocytes. Surprisingly, LCY-induced immunotoxicity was inhibited by MAA treatment, indicating that it effectively attenuated the LCY-induced changes described above. Overall, we concluded that MAA treatment could ameliorate LCY-induced necroptosis and immune dysfunction by inhibiting the ROS-mediated NF-κB signaling in lymphocytes. It provides insights into the protection of farmed fish from agrobiological threats in fish under LCY and the value of MAA applications in aquaculture.

Astaxanthin suppresses oxidative stress and calcification in vertebral cartilage endplate via activating Nrf-2/HO-1 signaling pathway

BACKGROUND

Cartilage endplate (CEP) degeneration is an important initiating factor leading to intervertebral disc degeneration (IVDD). Astaxanthin (Ast) is a natural lipid-soluble and red-orange carotenoid which possesses various biological activities, including antioxidant, anti-inflammatory, and anti-aging effects in multiple organisms. However, the effects and mechanism of Ast on endplate chondrocytes remain largely unknown. The objective of the current study was to investigate the effects and of Ast on CEP degeneration and its underlying molecular mechanisms.

METHODS

Tert-butyl hydroperoxide (TBHP) was used to mimic the IVDD pathological environment. We investigated the effects of Ast on the Nrf2 signaling pathway and damage-associated events. The IVDD model was constructed by surgical resection of L4 posterior elements to explore the role of Ast in vivo.

RESULTS

We found that the activation of the Nrf-2/HO-1 signaling pathway was enhanced by Ast, thus promoted mitophagy process, inhibited oxidative stress and CEP chondrocytes ferroptosis, eventually ameliorated extracellular matrix (ECM) degradation, CEP calcification and endplate chondrocytes apoptosis. Knockdown of Nrf-2 using siRNA inhibited Ast induced mitophagy process and its protective effect. Moreover, Ast inhibited oxidative stimulation-induced NF-κB activity and could ameliorate the inflammation response. The results also were confirmed by experiments in vivo, Ast alleviated IVDD development and CEP calcification.

CONCLUSIONS

Ast could protect vertebral cartilage endplate against oxidative stress and degeneration via activating Nrf-2/HO-1 pathway. Our results imply that Ast may serve as a potential therapeutic agent for IVDD progression and treatment.

Optimizing heterotrophic production of Chlorella sorokiniana SU-9 proteins potentially used as a sustainable protein substitute in aquafeed

Alternative protein sources for the reduction/replacement of fish meal in aqua-feeds are in urgent demand. Microalgae are considered sustainable protein sources for aquaculture due to their high-quality proteins with a complete profile of essential amino acids. This study examined the heterotrophic production of proteins from Chlorella sorokiniana SU-9. Culture parameters for maximal biomass and protein production are as follows: glucose - 10 g/L glucose, sodium nitrate - 1.5 g/L, and iron - 46 μM iron in BG-11 medium. Under optimal conditions, biomass content, protein content and protein productivity of SU-9 reached 4.14 ± 0.20 g/L, 403 ± 33 mg/g and 382 ± 36 mg/L/d, respectively. The protein profile of Chlorella sorokiniana SU-9 is comparable to fishmeal and soybean meal. The essential amino acids arginine, lysine and cysteine, along with glutamine and glutamate, were high. The production cost of SU-9 can be significantly reduced under heterotrophic cultivation conditions, making it a potential protein substitute in aquafeed.

The underestimated importance of fertilizer in aquacultural phosphorus budget: Case of Chinese mitten crab

China's reliance on aquaculture has intensified to satisfy the growing human demand for high-quality animal protein, making it the only country whose aquaculture production has greatly exceeded that of capture fishery for a long time. Previous studies have shown that phosphorus (P) is a limiting nutrient for freshwater eutrophication; therefore, the quantification of P flows in freshwater aquaculture is of great importance for improving aquaculture efficiency and reducing environmental pollution. In this study, life cycle assessment (LCA) and substance flow analysis (SFA) are combined to develop a life cycle P flow model for Chinese mitten crab (Eriocheir sinensis) culture and calculate the P inputs, outputs and net change in stock. The results show a relatively low P use efficiency (4 %) in Chinese mitten crab. Among all life-cycle stages, the maximum P input occurs during adult crab cultivation, when feed is continuously added to maintain appropriate nutrition levels and increase body weight. In addition, fertilizer is often neglected in the existing accounts but accounts for 24 % of the total P inputs. On the output side, approximately 86 % of the P accumulates in sediment, indicating the potential of sediment recycling as a nutrient source in agriculture. This study provides an updated quantitative method for describing nutrient flows within freshwater aquaculture systems and will contribute to decision-making in pollution control of intensive freshwater aquaculture activities.

Transcriptomics revealed the effect of astaxanthin on apoptosis and immunity of the adult prawn of Exopalaemon carinicauda

Astaxanthin (Axn), a common aquatic feed additive, can enhance immunity, improve the antioxidant capacity of the crustacean and then improve the anti-stress ability of crustaceans. Exopalaemon carinicauda (E. carinicauda) is an economically important fishery species in China that has been found that dietary Axn can significantly increase ACP and AKP compared to a control diet for shrimp hepatopancreas in this study. RNA-sequencing and comparative transcriptomic analyses were utilized to explore changes in E. carinicauda gene expression following Axn feeding. Differential gene expression analyses comparing the control and Axn groups identified 631 transcripts that were differentially expressed following Axn feeding, of which 314 and 317 were respectively upregulated and downregulated. Functional enrichment analyses of these genes revealed their enrichment in 22 Gene Ontology categories and 11 KEGG pathways. In the GO and KEGG enrichment analysis, it was found that dietary astaxanthin can regulate the gene expression level of adult E. carinicauda. Many of the signal pathways enriched by these genes are related to immunity, apoptosis and anti-stress. In addition, through KEGG enrichment analysis, it was found that dietary Axn could also regulate the amino acid metabolism of hepatopancreas of adult E. carinicauda. The comprehensive comparative transcriptomic analysis showed that Axn could improve the hepatopancreatic immunity and anti-apoptosis ability of adult E. carinicauda.

Effect of Astaxanthin on the Antioxidant Capacity and Intestinal Microbiota of Tsinling Lenok Trout (Brachymystax lenok tsinlingensis)

Astaxanthin (Ast) has been shown to be beneficial for the antioxidant capacity, immune system, and stress tolerance of fish. This study was conducted to investigate the effects of dietary supplementation of Ast on the antioxidant capacity and intestinal microbiota of tsinling lenok trout. We formulated four diets with 0 (CT), 50 (A50), 100 (A100), and 150 (A150) mg/kg Ast. The results showed that Ast increased total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px), lysozyme (LZM), and catalase (CAT) activities. Malondialdehyde (MDA) content was lower in A150 and A100 than in CT (P < 0.05). Furthermore, the activities of acid phosphatase (ACP) were higher in A100 and A150 than in CT (P < 0.05). We harvested the midgut and applied next-generation sequencing of 16S rDNA. Compared to the control group, the Ast group had a greater abundance of Halomonas. Functional analysis showed that polycyclic aromatic hydrocarbon degradation was significantly higher with Ast, while novobiocin biosynthesis and C5-branched dibasic acid metabolism were significantly lower with Ast. In conclusion, Ast could enhance the antioxidant capacity, non-specific immunity, and intestinal health of tsinling lenok trout.

Garlic Powder Supplementation Improves Growth, Nonspecific Immunity, Antioxidant Capacity, and Intestinal Flora of Chinese Mitten Crabs (Eriocheir sinensis)

This study was conducted to survey the effects of garlic powder on growth performance, nonspecific immunity, antioxidant capacity, and intestinal flora structure of Chinese mitten crabs. Altogether, 216 crabs which originally weigh 20.71 ± 0.13 g were randomly allocated into three treatment groups with 6 replicates of 12 crabs per replicate. The control group (CN) was fed a basal diet, while the other two groups were fed the basal diet supplemented with 1000 mg/kg (GP1000) and 2000 mg/kg (GP2000) garlic powder, respectively. This trial lasted 8 weeks. The results showed that the supplementation of garlic powder improved the final body weight, weight gain rate, and specific growth rate of the crabs (P < 0.05). Meanwhile, in serum, better nonspecific immune was confirmed by the enhancement of phenoloxidase and lysozyme levels, with the improvement of phosphatase activities in GP1000 and GP2000 (P < 0.05). On the other hand, the levels of total antioxidant capacity, glutathione peroxidases, and total superoxide dismutase in serum and hepatopancreas were increased (P < 0.05) while malondialdehyde content declined (P < 0.05) as the garlic powder was added to the basal diet. And, catalase in serum also shows an increase (P < 0.05). In both GP1000 and GP2000, genes related to antioxidant and immunity, for instance, Toll-like receptor 1, glutathione peroxidase, catalase, myeloid differentiation factor 88, TuBe, Dif, relish, crustins, antilipopolysaccharide factor, lysozyme, and prophenoloxidase mRNA expression levels, were increased (P < 0.05). The abundance of Rhizobium and Rhodobacter was reduced by adding garlic powder (P < 0.05). This study indicated that dietary addition of garlic powder promoted growth, enhanced nonspecific immunity and antioxidant capacity, activated Toll pathway, IMD pathway, and proPO system, increased antimicrobial peptide expression, while simultaneously improving the intestinal flora of Chinese mitten crabs.

Effects of dietary glyceryl monolaurate supplementation on growth performance, non-specific immunity, antioxidant status and intestinal microflora of Chinese mitten crabs

This study aims to investigate the effects of glycerol monolaurate (GML) on growth performance, non-specific immunity, antioxidant capacity and intestinal microflora in Chinese mitten crabs. The crabs were randomly arranged to three experimental diets groups containing 0 (control group), 1000 mg/kg GML (GML1000 group), and 2000 mg/kg GML (GML2000 group), respectively. After 8 weeks of breeding, results showed a better growth performance in GML2000 group, with a higher PWG, SGR and lower FCR (P < 0.05). Meanwhile, in GML2000 group the activities of phenoloxidase, alkaline phosphatase, acid phosphatase and lysozyme in hemolymph were increased (P < 0.05), also the activities of hemolymph and hepatopancreas superoxide dismutase (SOD) and glutathione peroxidase (GPx) were increased in hepatopancreas (P < 0.05). While malondialdehyde (MDA) concentrations were lower significantly (P < 0.05) both in GML1000 and GML2000 groups. Furthermore, the mRNA expression of TLR1, TLR2, which related to the Toll pathway were increased (P < 0.05). Supplementation of 2000 mg/kg GML up-regulated the expression of ALF and LZM (P < 0.05), and down-regulated the expression of caspase-3 (P < 0.05). The abundance of Firmicutes increased in GML2000 group (P < 0.05), and Shewanella was significantly increased (P < 0.05) in both GML1000 and GML2000 groups. In conclusion, dietary supplemented with GML enhanced the growth performance and antioxidant capacity, enhanced hemolymph immune enzymes activities and antimicrobial peptides expression through regulating the proPO system and Toll pathway, and improved gut microflora in Chinese mitten crabs.

Dietary astaxanthin improves the antioxidant capacity, immunity and disease resistance of coral trout (Plectropomus leopardus)

The effects of astaxanthin on growth performance, digestive enzyme activity, antioxidant capacity, immune ability, resistance to Vibrio harveyi infection of coral trout (Plectropomus leopardus, initial weight 17.44 ± 0.05 g) were studied by 8-week feeding trial. Four iso-nitrogenous and iso-lipidic experimental diets containing astaxanthin 0 (A0), 0.05 (A1), 0.1 (A2) and 0.2 (A3) g/kg were formulated with the addition of Haematococcus pluvialis powder (astaxanthin content accounts for 100 g/kg) of 0, 0.5, 1.0 and 2.0 g/kg, separately. The feeding experiment lasted for 56 days, and it was found that supplementing the diet with astaxanthin-rich H. pluvialis powder had no significant impact on the growth performance about coral trout (P > 0.05). Compared with the A0 group, the activities of amylase, lipase, and trypsin in the liver of the A2 group was dramatically increased (P < 0.05); catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities and total antioxidant capacity (T-AOC) level in serum and liver were dramatically higher in the A2 group before as well as after the challenge (P < 0.05); after the challenge, the acid phosphatase (ACP) and lysozyme (LZ) activities, and complement (C3 and C4) contents in serum and liver were significantly raised for the A2 group (P < 0.05); the liver relative expressions of copper-zinc superoxide dismutase (sod-1), manganese superoxide dismutase (sod-2), cat, acp6, akp, lz-c, immunoglobulin M (igm), c3, and c4-b in the A2 group were significantly up-regulated before and after the challenge (P < 0.05); the rate of survival follow V. harveyi challenge in the group A2 was dramatically higher (P < 0.05). In summary, this study indicated that adding 1.0 g/kg astaxanthin-rich H. pluvialis powder (the content of astaxanthin is 0.091 g/kg) could improve the digestive enzyme activity, antioxidant capacity, immunity, and the ability to resist the challenge of V. harveyi in coral trout.

The effects of ammonia-N stress on immune parameters, antioxidant capacity, digestive function, and intestinal microflora of Chinese mitten crab, Eriocheir sinensis, and the protective effect of dietary supplement of melatonin

Ammonia nitrogen pollution seriously affects the economic benefits of Chinese mitten crab (Eriocheir sinensis) farming. In this study, we first evaluated the protective effects of melatonin (MT) on immune parameters, antioxidant capacity, and digestive enzymes of E. sinensis under acute ammonia nitrogen stress. The results showed that ammonia-N stress significantly decreased the antibacterial ability of crabs, nevertheless MT could significantly improve it under ammonia-N stress (P < 0.05). Ammonia-N group hemolymph antioxidant capacity indicators (T-AOC, T-SOD, GSH-Px) were significantly decreased than control (p < 0.05), while the MT ammonia-N group hemolymph T-SOD activity significantly increased than ammonia-N group (p < 0.05). For hepatopancreas, ammonia-N group GSH-PX activity significantly decreased than control group, but MT ammonia-N group was significant increased than ammonia-N (p < 0.05). Ammonia-N stress has significantly increased the content of MDA in hemolymph and hepatopancreas (p < 0.05), but MT ammonia-N treatment significantly decreased than ammonia-N group (p < 0.05). Compared with the control group, ammonia-N significantly reduced the activities of Trypsin in the intestine and hepatopancreas (p < 0.05), while MT ammonia-N group can significantly improve the intestinal trypsin activity than ammonia-N (p < 0.05). The intestinal microbiota of E. sinensis results showed that ammonia-N stress significantly decreased the relative abundance of Bacteroidetes (p < 0.05). Ammonia-N stress significantly decreased the Dysgonomonas and Rubellimicrobium, and the Citrobacter significantly increased. In summary, melatonin has a protective effect on E. sinensis under ammonia-N stress. Acute ammonia-N stress may lead to the decrease of probiotics and the increase of pathogenic bacteria, which may be closely related to the impairment of digestive function and immune function.

Effects of Dietary Phaffia rhodozyma Astaxanthin on Growth Performance, Carotenoid Analysis, Biochemical and Immune-Physiological Parameters, Intestinal Microbiota, and Disease Resistance in Penaeus monodon

The present study aimed to investigate the effect of dietary astaxanthin (Ast) from Phaffia rhodozyma on growth performance, survival, carotenoid content, the activity of antioxidant and immune-related enzymes, intestinal microbiota comparison, and disease resistance against Vibrio parahaemolyticus in Penaeus monodon. Juveniles (average weight 3.15 ± 0.12 g) were fed with six experimental diets supplemented with 0 (Control), 20.5, 41, 61.5, 82, and 102.5 mg/kg of Ast (defined as diet A–D) in triplicate for 56 days. The results indicated that shrimp fed with Ast supplementation significantly (p < 0.05) improved growth performance compared with the control. Furthermore, significantly (p < 0.05) increased survival and decreased feed conversion ratio (FCR) demonstrated the beneficial effects of dietary Ast on enhancing nutrient utilization and ultimately improving the growth and survival of shrimp. Furthermore, shrimp fed with Ast including diet developed a deeper red color than the control, consistent with the significantly (p < 0.05) increased Ast deposition in the shrimp shell. Hemolymph-immunological parameters [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (AKP)] and hepatopancreatic antioxidant status [total antioxidant capacity (T-AOC), malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD)] were significantly (p < 0.05) affected by dietary Ast supplementation. Dietary increasing Ast levels significantly (p < 0.05) increased shrimp resistance performance to V. parahaemolyticus according to the LT₅₀ results in the current study, which may be caused by increased total carotenoid contents in shrimp tissues from all the Ast-supplemented treatments. Conversely, intestinal microbiota biodiversity and richness were not affected by dietary Ast. The best performances of growth, antioxidant status, immunological response, and carotenoid deposition were observed in diets E and F among all the Ast-supplemented treatments. Overall, all the data suggested that dietary P. rhodozyma Ast played a critical role in improving growth performance, achieving the desired coloration, increasing carotenoid content, and keeping better health status of shrimp. Based on these positive performances, P. rhodozyma Ast could gain the trust of the consumers as a natural source and provide a potential alternative for synthetic Ast using in the Penaeus monodon culture industry.

Dietary Supplementation of Astaxanthin Improved the Growth Performance, Antioxidant Ability and Immune Response of Juvenile Largemouth Bass (Micropterus salmoides) Fed High-Fat Diet

High-fat diet (HFD) usually induces oxidative stress and astaxanthin is regarded as an excellent anti-oxidant. An 8-week feeding trial was conducted to investigate the effects of dietary astaxanthin supplementation on growth performance, lipid metabolism, antioxidant ability, and immune response of juvenile largemouth bass (Micropterus salmoides) fed HFD. Four diets were formulated: the control diet (10.87% lipid, C), high-fat diet (18.08% lipid, HF), and HF diet supplemented with 75 and 150 mg kg^-1 astaxanthin (HFA1 and HFA2, respectively). Dietary supplementation of astaxanthin improved the growth of fish fed HFD, also decreased hepatosomatic index and intraperitoneal fat ratio of fish fed HFD, while having no effect on body fat. Malondialdehyde content and superoxide dismutase activity were increased in fish fed HFD, astaxanthin supplementation in HFD decreased the oxidative stress of fish. The supplementation of astaxanthin in HFD also reduced the mRNA levels of Caspase 3, Caspase 9, BAD, and IL15. These results suggested that dietary astaxanthin supplementation in HFD improved the growth performance, antioxidant ability and immune response of largemouth bass.