Comparative study of the key enzymes and biochemical substances involved in the energy metabolism of Pacific white shrimp, Litopenaeus vannamei, with different ammonia-N tolerances

Effect of paprika extracts on growth performance, haemolymph chemistry, intestinal microbiota and antioxidant enzyme activities of white-leg shrimp (Litopenaeus vannamei)

This study aims to evaluate the effects of paprika extract on the survival rate, growth performance and stimulation of the innate immune system of Litopenaeus vannamei. In this experiment, 240 healthy shrimp (3.22 ± 0.12 g) were randomly divided into four groups. The shrimp were fed diets with different concentrations of paprika oil extracts (0%, 0.5%, 1% and 2%) for 8 weeks. The results showed that growth performance, urea, uric acid, creatinine, cholesterol levels, aspartate aminotransferase and alkaline phosphatase activities were not significantly affected by adding paprika extract to the shrimp diet (p > 0.05). Diets containing 1% and 0.5% paprika extract showed the highest levels of total protein and triglyceride, respectively (p < 0.05). There was a significant decrease in haemolymph glucose concentration in shrimp-fed diets containing 1% and 2% paprika extract (p < 0.05). Moreover, a diet containing 0.5% paprika extract resulted in the highest levels of total heamocyte count, hyaline cells and large-granular cells in shrimp (p < 0.05). Higher catalase and superoxide dismutase activities were also exhibited in the paprika groups (p < 0.05). Vibrio sp. bacteria were not significantly reduced by paprika extract in the intestines of L. vannamei (p > 0.05). A significant decrease in heterotrophic bacteria was observed with increasing extract concentrations (p < 0.05). The shrimp culture industry can utilize paprika extract as a cost-effective, efficient and environmentally friendly immune stimulant at a concentration of 0.5%.

Toxicity of Ammonia Stress on the Physiological Homeostasis in the Gills of Litopenaeus vannamei under Seawater and Low-Salinity Conditions

Ammonia is a major water quality factor influencing the survival and health of shrimp, among which the gill is the main effector organ for ammonia toxicity. In this study, we chose two types of Litopenaeus vannamei that were cultured in 30‱ seawater and domesticated in 3‱ low salinity, respectively, and then separately subjected to ammonia stress for 14 days under seawater and low-salinity conditions, of which the 3‱ low salinity-cultured shrimp were domesticated from the shrimp cultured in 30‱ seawater after 27 days of gradual salinity desalination. In detail, this study included four groups, namely the SC group (ammonia-N 0 mg/L, salinity 30‱), SAN group (ammonia-N 10 mg/L, salinity 30‱), LC group (ammonia-N 0 mg/L, salinity 3‱), and LAN group (ammonia-N 10 mg/L, salinity 3‱). The ammonia stress lasted for 14 days, and then the changes in the morphological structure and physiological function of the gills were explored. The results show that ammonia stress caused the severe contraction of gill filaments and the deformation or even rupture of gill vessels. Biochemical indicators of oxidative stress, including LPO and MDA contents, as well as T-AOC and GST activities, were increased in the SAN and LAN groups, while the activities of CAT and POD and the mRNA expression levels of antioxidant-related genes (nrf2, cat, gpx, hsp70, and trx) were decreased. In addition, the mRNA expression levels of the genes involved in ER stress (ire1 and xbp1), apoptosis (casp-3, casp-9, and jnk), detoxification (gst, ugt, and sult), glucose metabolism (pdh, hk, pk, and ldh), and the tricarboxylic acid cycle (mdh, cs, idh, and odh) were decreased in the SAN and LAN groups; the levels of electron-transport chain-related genes (ndh, cco, and coi), and the bip and sdh genes were decreased in the SAN group but increased in the LAN group; and the level of the ATPase gene was decreased but the cytc gene was increased in the SAN and LAN groups. The mRNA expression levels of osmotic regulation-related genes (nka-β, ca, aqp and clc) were decreased in the SAN group, while the level of the ca gene was increased in the LAN group; the nka-α gene was decreased in both two groups. The results demonstrate that ammonia stress could influence the physiological homeostasis of the shrimp gills, possibly by damaging the tissue morphology, and affecting the redox, ER function, apoptosis, detoxification, energy metabolism, and osmoregulation.

Combined effects of dietary carbohydrate levels and ammonia stress on growth, antioxidant capacity and glucose metabolism in juvenile oriental river prawn (Macrobrachium nipponense)

Ammonia is a common environmental stress factor that constrains aquaculture industry development. This study evaluated the effect of carbohydrate levels and ammonia stress in oriental river prawn (Macrobrachium nipponense). The experiment had six treatments containing two water ammonia levels (0 and 5 mg/L) and three dietary carbohydrate levels (low carbohydrate diet (LCD, 10%), medium carbohydrate diet [MCD, 20%], and high carbohydrate diet [HCD, 30%]), and lasted six weeks. The results showed that the prawns fed on MCD had higher weight gain than those fed on LCD and HCD during ammonia stress. Moreover, the prawns fed on MCD had significantly lower acid phosphatase and alkaline phosphatase activities during ammonia stress. Feeding the prawns on the MCD increased B cells in the hepatopancreas during ammonia stress. Interestingly, the prawns fed on MCD had significantly lower superoxide dismutase activity compared to LCD and HCD during ammonia stress. Moreover, the prawns fed on MCD had significantly lower pyruvate kinase activity and pyruvate and lactic acid contents, while those fed on LCD had significantly higher succinic dehydrogenase, 6-phosphogluconic dehydrogenase, and phosphoenol pyruvate carboxykinase activities during ammonia stress. The prawns fed on the MCD increased significantly glutaminase activity and decreased the ammonia content in the serum during ammonia exposure. In addition, feeding the prawns on MCD decreased significantly the expression of apoptosis and inflammation-related genes. Taken together, the MCD supplied energy required to counteract ammonia stress, which increased growth, improved antioxidant capacity, facilitated ammonia excretion, and alleviated inflammation and apoptosis of the oriental river prawn.

Impacts of long-time transportation on whiteleg shrimp (Penaeus vannamei) muscle quality and underlying biochemical mechanisms

BACKGROUND

Shrimp is widely consumed around the world. Since muscle is the primary edible component of shrimp, muscle quality (particularly texture) has a direct impact on the economic value of shrimp products. However, reports on the shrimp muscle quality influenced by transportation are rather limited, and the underlying mechanism remains unknown.

RESULTS

During the simulated transportation, the water pH and total ammonia-nitrogen content and un-ionized ammonia contents were elevated. Furthermore, reductions in shrimp muscle water-holding capacity, hardness, and shear value with intensive myofibrillar protein degradation were detected. Simulated transportation decreased the pH and glycogen content of shrimp muscle while increasing lactic dehydrogenase activity and lactate content, resulting in an elevated level of free calcium ions and increased μ-calpain and general proteolytic activities. Water exchange could improve the water quality and reduce the mortality of shrimp during transportation, as well as decrease muscle textural softening by alleviating these stress responses.

CONCLUSIONS

Maintaining water quality and, in particular, reducing ammonia are critical to improving shrimp survival and muscle quality during live transportation. This study is of great significance for the better maintenance of the textural properties of shrimp meat. © 2023 Society of Chemical Industry.

Integrated Transcriptomic and Metabolomic Analyses Reveal Low-Temperature Tolerance Mechanism in Giant Freshwater Prawn Macrobrachium rosenbergii

Water temperature, as an important environmental factor, affects the growth and metabolism of aquatic animals and even their survival. The giant freshwater prawn (GFP) Macrobrachium rosenbergii is a kind of warm-water species, and its survival temperature ranges from 18 °C to 34 °C. In this study, we performed transcriptomic and metabolomic analyses to clarify the potential molecular mechanism of responding to low-temperature stress in adult GFP. The treatments with low-temperature stress showed that the lowest lethal temperature of the GFP was 12.3 °C. KEGG enrichment analyses revealed that the differentially expressed genes and metabolites were both enriched in lipid and energy metabolism pathways. Some key genes, such as phosphoenolpyruvate carboxykinase and fatty acid synthase, as well as the content of the metabolites dodecanoic acid and alpha-linolenic acid, were altered under low-temperature stress. Importantly, the levels of unsaturated fatty acids were decreased in LS (low-temperature sensitive group) vs. Con (control group). In LT (low-temperature tolerant group) vs. Con, the genes related to fatty acid synthesis and degradation were upregulated to cope with low-temperature stress. It suggested that the genes and metabolites associated with lipid metabolism and energy metabolism play vital roles in responding to low-temperature stress. This study provided a molecular basis for the selection of a low-temperature tolerant strain.

Adverse effects of chronic ammonia stress on juvenile oriental river prawn (Macrobrachium nipponense) and alteration of glucose and ammonia metabolism

Ammonia is one of the common stress factors in aquaculture. However, the effect of chronic ammonia exposure in juvenile oriental river prawn (Macrobrachium nipponense) is currently unexplored. This study explored the effects of chronic ammonia on juvenile healthy oriental river prawns. Fifty prawns (0.123 ± 0.003 g) were exposed to 0, 5, and 15 mg/L total ammonia nitrogen (TAN) in triplicates for 28 days. The effects of chronic ammonia challenge were evaluated on growth, antioxidant capacity, hepatopancreas and gill morphology, and glucose and ammonia metabolism. The results showed that, the chronic ammonia exposure reduced significantly survival rate and weight gain of prawns. The prawns exposed to 15 mg/L ammonia had induced oxidative stress. However, the prawn exposed to 15 mg/L ammonia had significantly lower aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and acid phosphatase activities in the serum. Furthermore, exposure of prawns to 15 mg/L ammonia increased the activities of hexokinase, pyruvate kinase, pyruvate and lactic acid content, and glutamine synthase activity. However, the prawns exposed to 15 mg/L ammonia, reduced succinic dehydrogenase, 6-phosphogluconic dehydrogenase, phosphoenolpyruvate carboxykinase, glutamate synthase, and glutamate dehydrogenase activities but increased ammonia content in serum. The exposure of ammonia deformed lumen, damaged basement membrane and decreased secretory cells in the hepatopancreas, disordered gill epithelial and pillar cells, and caused gill filament base vacuolation. Our study indicates that chronic ammonia stress impairs growth performance, tissue morphology, induces oxidative stress, and alters glucose and ammonia metabolism in juvenile oriental river prawns.

Effect of ammonia stress on AMPK regulating-carbohydrate and lipid metabolism in Chinese striped-neck turtle (Mauremys sinensis)

In aquatic organisms, ammonia is one of the major factors that affect energy levels when it exceeds its optimal concentration. Numerous studies have examined the effects of ammonia on aquatic animals, but its effect on metabolism is still unknown. The effect of ammonia on carbohydrates and lipid metabolism in the Chinese striped neck turtle (Mauremys sinensis) was investigated in this study by exposing the turtle to two different ammonia concentrations (A100: 1.53 mg L^-1) and (A200: 2.98 mg L^-1) for 24 and 48 h, respectively. Our results showed that the mRNA expression of adenosine monophosphate-activated protein kinase α1 (AMPKα1) significantly increased only in A100 at 24 h, whereas its activity increased in both ammonia-exposed groups. The two AMPK-regulated transcription factors responsible for carbohydrate metabolism also exhibited changes in ammonia-treated groups, as hepatocyte nuclear factor-4-alpha (HNF4α) increased and forkhead box protein O1 (FoxO1) decreased. The expression of phosphofructokinase (PFK) and glucose-6-phosphatase (G-6-PAS) was subsequently downregulated. In addition, transcription factors, carbohydrate-responsive element-binding protein (ChREBP), and sterol regulatory element-binding protein 1c (SREBP-1c), which are known to be involved in lipogenesis, were suppressed. These downstream genes include fatty acid synthase, stearoyl CoA desaturase, and acetyl-CoA carboxylase (FAS, SCD-1 and ACC). Moreover, the glucose content decreased, whereas the triglyceride content increased significantly in A200 at 24 h. We concluded that AMPK signaling inhibits gluconeogenesis and lipogenesis, and promotes glycolysis to meet energy demand under stressful conditions in M. sinensis.

Effects of dietary Ginkgo biloba leaf extract on growth performance, immunity and environmental stress tolerance of Penaeus vannamei

Ginkgo biloba leaf extract (GBE) has been extensively used in the treatment of diseases due to its anti-inflammatory, antioxidant, and immunomodulatory effects. In aquaculture, GBE is widely used as a feed additive, which is important to enhance the immunity of aquatic animals. The current study evaluated the effects of adding GBE to the diet of Penaeus vannamei (P. vannamei) under intensive aquaculture. The GBE0 (control group), GBE1, GBE2, and GBE4 groups were fed a commercial feed supplemented with 0.0, 1.0, 2.0, and 4.0 g/kg GBE for 21 days, respectively. The results showed that dietary GBE could alleviate hepatopancreas tissue damage and improve the survival rate of shrimp, and dietary 2 g/kg GBE could significantly increase the total hemocyte count (THC), the hemocyanin content, the antioxidant gene's expression, and the activity of their encoded enzymes in P. vannamei. Furthermore, transcriptome data revealed that immunity-related genes were upregulated in the GBE2 group compared with the GBE0 group after 21 days of culture. Drug metabolism-cytochrome P450, sphingolipid metabolism, linoleic acid metabolism, glycerolipid metabolism, fat digestion and protein digestion and absorption pathways were significantly enriched, according to KEGG results. Surprisingly, all of the above KEGG-enriched pathways were significantly upregulated. These findings demonstrated that supplementing P. vannamei with 2 g/kg GBE improved its environmental adaptability by improving immunity, lipid metabolism, and detoxification. In this study, a comprehensive evaluation of the effects of dietary GBE on the intensive aquaculture of P. vannamei was conducted to provide a reference for the healthy culture of P. vannamei.

Comparison of lipid metabolism between broodstock and hybrid offspring in the hepatopancreas of juvenile shrimp (Macrobrachium nipponense): Response to chronic ammonia stress

Ammonia nitrogen is a major pollutant that causes great physiological harm to crustaceans in culture. In this study, we conducted a 28 day chronic ammonia nitrogen stress experiment with broodstock populations (Dianshan, DS) and hybrid offspring populations (DS ♀ × CD (Changjiang ♂ × Dongting ♀), SCD) exposed to 0, 1 and 10 mg/L of ammonia concentrations. A 28 day feeding trial and chronic ammonia nitrogen stress were used to investigate the effects on the growth performance, histological structure and lipid metabolism of juvenile shrimp, Macrobrachium nipponense. Our results indicated that survival rates in the SCD groups were significantly higher than those in the DS groups, whereas weight and length gain rates were not significantly different between the groups (p > 0.05). Histological structure results showed that the number of vacuoles in the DS group was significantly higher than that in the SCD group and hepatopancreas cell structures were disrupted in the ammonia treatment groups. The results of oil red staining showed that the number of lipid droplets increased significantly with the increase in ammonia concentration. As the ammonia concentration increased, fatty acid contents, lipid enzyme activities and lipid metabolism-related gene expression all tended to rise. In conclusion, ammonia nitrogen exposure caused damage to the hepatopancreas structure of juvenile shrimp and disturbed the lipid metabolism of the hepatopancreas. In addition, the SCD population had stronger stress resistance than the DS population when subjected to the same concentration of ammonia nitrogen stress.