Characterization and expression of arginine kinase 2 from Macrobrachium nipponense in response to salinity stress

Chronic toxicity of biodegradable microplastic (Polylactic acid) to Daphnia magna: A comparison with polyethylene terephthalate

The increase in the usage of biodegradable microplastics (MPs) as an alternative to conventional plastics has necessitated comprehensive ecotoxicity assessments of biodegradable MPs alongside conventional MPs. This study aimed to assess ecotoxicity of biodegradable polylactic acid (PLA) MPs at concentration of 1 and 5 mgL-1 including a genetic analysis of Daphnia magna, and compared to effects of conventional polyethylene terephthalate (PET) MPs. The survival rate for D. magna exposed to 5 mg L-1 of PLA-MPs declined to 52.4 %, signifying a higher rate of mortality when contrasted with PET-MPs, which exhibited 85.7 % survival rate. Chronic exposure to 1 and 5 mgL-1 PLA-MPs resulted in a decrease of offspring, while increasing the sex ratio and deformed embryo. Interestingly, down-regulation of the SOD and AK genes was observed in D. magna after exposure to 5 mgL-1 of PLA-MPs, while 1 mgL-1 of PLA-MPs up-regulated. These results means that 5 mgL-1 PLA-MP could not produce energy and cope with oxidative stress, resulting in high mortality, and 1 mgL-1 of MP was maintained survival due to energy production and antioxidant action. This study contributes to our understanding of biodegradable microplastics (BMPs) toxic effects on D. magna which could be similar to conventional MPs and provide the importance of ecotoxicological data for risk assessment of BMPs in aquatic organisms.

Label-free quantification proteomics analysis reveals acute hyper-osmotic responsive proteins in the gills of Chinese mitten crab (Eriocheir sinensis)

Chinese mitten crab (Eriocheir sinensis) is a typical euryhaline crustacean to study osmotic regulation of crustaceans. Osmotic-regulation of Chinese mitten crab is a complex process. In order to study the osmotic-regulation related proteins of Chinese mitten crab, we domesticated Chinese mitten crab for 144 h with 25 salinity sea water (SW) and 0 salinity fresh water (FW) respectively, and then analyzed the proteome of its posterior gills. A total of 1453 proteins were identified by label free proteomics. Under the threshold of 2 fold change (FC), 242 differentially expressed proteins (DEPs) were screened, including 122 up-regulated DEPs and 120 down-regulated DEPs. GO database and KEGG database were used to annotate and enrich DEPs. It was found that DEPs were significantly enriched in energy metabolism, signal transduction, ion transport, actin cytoskeleton, immunity, lipid metabolism, amino acid metabolism and other biological functions. After 144 h of high salinity stress, the energy metabolism of Chinese mitten crab decreased and the expression of actin and cytoskeleton protein increased. In order to cope with oxidative damage caused by high salinity, Chinese mitten crab improved its immunity and antioxidant capacity.

Role of myo-inositol supplementation against toxicity of excessive dietary copper in Pacific white shrimp Litopenaeus vannamei

Raw materials for making dried shrimp (a type of foodstuff) are mostly from farmed shrimp and preliminary findings indicated that head copper (Cu) concentrations in some commercial dried shrimp products exceeded the safe limit specified in pollution-free aquatic products (50 mg/kg), which may influence food safety. Therefore, a 63-day feeding trial was conducted to explore effects of dietary Cu concentrations on accumulation of Cu in tissues, growth performance, immune response and antioxidant status of Pacific white shrimp (Litopenaeus vannamei). Moderating effect of myo-inositol (MI, adding 200 mg/kg diet) on the adverse impacts caused by excessive dietary Cu was also investigated. 600 shrimp (initial weight: 0.89 ± 0.00 g) were divided into five groups: 37.08 mg Cu/kg diet group (control group), 62.57 mg Cu/kg diet group, 125.99 mg Cu/kg diet group, 63.41 mg Cu/kg diet group (supplemented with MI) and 119.19 mg Cu/kg diet group (supplemented with MI). The results showed that dietary Cu concentrations increased from 37.08 to over 62.57 mg/kg, hepatopancreas Cu concentrations raised from 29.04 to 233.43-263.65 mg/kg, and muscle Cu concentrations only increased from 6.22 to 6.99-8.39 mg/kg. Report to control group, excessive Cu concentration (125.99 mg/kg) didn't significantly affect growth performance, but it notably reduced whole body lipid content and immune response, induced oxidative stress and damaged the hepatopancreas structure, which was ameliorated by MI supplementation. The results suggested that consuming shrimp head and its processed products weren't recommended. Cu concentrations of commercial feeds for Pacific white shrimp should be controlled below 62.57 mg/kg. Additionally, MI supplementation mitigated the negative impacts induced by excessive dietary Cu.

Transcriptome Analysis to Study the Molecular Response in the Gill and Hepatopancreas Tissues of Macrobrachium nipponense to Salinity Acclimation

Macrobrachium nipponense is an economically important prawn species and common in Chinese inland capture fisheries. During aquaculture, M. nipponense can survive under freshwater and low salinity conditions. The molecular mechanism underlying the response to salinity acclimation remains unclear in this species; thus, in this study, we used the Illumina RNA sequencing platform for transcriptome analyses of the gill and hepatopancreas tissues of M. nipponense exposed to salinity stress [0.4‰ (S0, control group), 6‰ (S6, low salinity group), and 12‰ (S12, high salinity group)]. Differentially expressed genes were identified, and several important salinity adaptation-related terms and signaling pathways were found to be enriched, such as “ion transport,” “oxidative phosphorylation,” and “glycometabolism.” Quantitative real-time PCR demonstrated the participation of 12 key genes in osmotic pressure regulation in M. nipponense under acute salinity stress. Further, the role of carbonic anhydrase in response to salinity acclimation was investigated by subjecting the gill tissues of M. nipponense to in situ hybridization. Collectively, the results reported herein enhance our understanding of the mechanisms via which M. nipponense adapts to changes in salinity.

Comparison of immune defense and antioxidant capacity between broodstock and hybrid offspring of juvenile shrimp (Macrobrachium nipponense): Response to acute ammonia stress

Ammonia is a major environmental pollutant in the aquatic system that poses a great threat to the health of shrimp. Macrobrachium nipponense, as one of the large-yield farmed shrimp, is facing germplasm degradation. Genetic improvement through hybridization is one of the effective methods to solve this problem. However, there are few studies on the effects of ammonia nitrogen on the germplasm resources of M. nipponense. In this study, the broodstock populations (Dianshan, DS) and hybrid offspring (DS ♀ × CD [Changjiang, CJ ♂ × Dongting, DT ♀], SCD) were exposed to 0, 5, or 20 mg/L of ammonia for 96 h. The survival rate of the SCD group was greater than the DS group, although there were no significant differences in weight gain rate and length gain rate (p > 0.05). The number of positive cells and apoptosis rates in the DS group were significantly greater than in the SCD group after ammonia exposure (p < 0.05). As the ammonia concentration increased, the antioxidant enzyme activities in the SCD group were significantly higher than DS group, while the hepatotoxicity enzyme activities in the SCD group were significantly lower than DS group (p < 0.05). The trends in the expression of antioxidant- and immune-related genes were generally consistent with the activities of antioxidant enzymes. Our study found that the hybrid population had stronger stress resistance than their parent populations at the same ammonia concentration. This study confirms our speculation that hybrid population has a greater advantage in antioxidant immunity, which also provides reference for the follow-up study of chronic ammonia toxicity.

Differential expression and activity of arginine kinase between the American trypanosomatids Trypanosoma rangeli and Trypanosoma cruzi

Trypanosoma rangeli is a non-virulent hemoflagellate parasite infecting humans, wild and domestic mammals in Central and Latin America. The share of genotypic, phenotypic, and biological similarities with the virulent, human-infective T. cruzi and T. brucei, allows comparative studies on mechanisms of pathogenesis. In this study, investigation of the T. rangeli Arginine Kinase (TrAK) revealed two highly similar copies of the AK gene in this taxon, and a distinct expression profile and activity between replicative and infective forms. Although TrAK expression seems stable during epimastigotes growth, the enzymatic activity increases during the exponential growth phase and decreases from the stationary phase onwards. No differences were observed in activity or expression levels of TrAK during in vitro differentiation from epimastigotes to infective forms, and no detectable AK expression was observed for blood trypomastigotes. Overexpression of TrAK by T. rangeli showed no effects on the in vitro growth pattern, differentiation to infective forms, or infectivity to mice and triatomines. Although differences in TrAK expression and activity were observed among T. rangeli strains from distinct genetic lineages, our results indicate an up-regulation during parasite replication and putative post-translational myristoylation of this enzyme. We conclude that up-regulation of TrAK activity in epimastigotes appears to improve proliferation fitness, while reduced TrAK expression in blood trypomastigotes may be related to short-term and subpatent parasitemia in mammalian hosts.

Effects of nanoplastics on energy metabolism in the oriental river prawn (Macrobrachium nipponense)

Nanoplastics are common pollutants in aquatic environments and have attracted widespread research attention. However, few studies focus on the effects of nanoplastic exposure on energy metabolism in crustaceans. Accordingly, we exposed juvenile oriental river prawns (Macrobrachium nipponense) to different concentrations of 75-nm polystyrene nanoplastics (0, 5, 10, 20, and 40 mg/L) for 7, 14, 21, or 28 days. Thereafter, the effects of nanoplastic exposure on metabolite content, energy metabolism-related enzyme activity, and gene expression were evaluated. Our results showed that (1) with increasing nanoplastic concentration and exposure time, the survival rate decreased, while weight gain rate and molting number increased and then decreased; glycogen, triglyceride, and total cholesterol content all declined while lactic acid content increased with higher exposure to nanoplastic concentrations; (2) the activities of acetyl-CoA carboxylase (ACC), hexokinase (HK), carnitine palmitoyl transferase-1, pyruvate kinase (PK), lipase, and fatty acid synthase tended to decrease, while the activity of lactate dehydrogenase (LDH) increased. In particular, the activity of 6-phosphofructokinase exposed to 5 mg/L nanoplastics increased significantly (P < 0.05). (3) Expression of the metabolism-related genes 6-phosphate glucokinase (G-6-Pase), HK, PK, ACC, Acetyl-CoA-binding protein (ACBP), CPT-1, and fatty-acid-binding protein 10 (FABP 10) increased and then decreased, while expression of the LDH gene showed an upward trend. These results indicate that nanoplastics affect growth, enzyme activity, and the gene expression of energy metabolism in M. nipponense, and that high concentrations of nanoplastics have a negative impact on energy metabolism.