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The growth environment significantly influences the intestinal microbiota of aquatic organisms. We investigated the composition and functional differences in the intestinal microbiota of red claw crayfish (Cherax quadricarinatus) in rice fields (RB) and ponds (PB) by 16S rDNA high-throughput sequencing technology. The results indicate that the Shannon, Simpson, Sobs, Chao1, and ACE indices of PB are all higher than those of RB, demonstrating greater diversity and richness of intestinal microbiota. The dominant phyla in the intestinal microbiota of the Cherax quadricarinatus were Proteobacteria, Tenericutes, and Firmicutes. Tenericutes and Proteobacteria were significantly more abundant in the RB than in the PB, while Planctomycetes and Firmicutes were significantly more abundant in the PB than in the RB. The results of network correlation analysis indicate that Proteobacteria and Firmicutes exhibit strong connectivity with other microbial groups in the gut microbiota of Cherax quadricarinatus, showing significant centrality. They play an important role in the interactions within the gut microbiota community. The dominant bacterial genera in the Cherax quadricarinatus's gut were Citrobacter, Candidatus_Bacilloplasma, and Clostridium_sensu_stricto_1. The abundance of the genus Clostridium was significantly higher in the PB than in the RB, whereas the abundance of Candidatus_Hepatoplasma and Vibrio was significantly lower in the PB than in the RB. The prediction function of KEGG enrichment showed that the abundance of Amino acid metabolism, Biosynthesis of Other Secondary Metabolites, Transport and Catabolism, Cancers, and Nervous System, Substance Dependence were significantly higher in the PB, while the infectious diseases pathway was enriched in the RB. In summary, our results revealed significant differences in the composition and diversity of intestinal microbiota in the Cherax quadricarinatus between rice paddy and pond farming environments. The intestinal microbiota of the Cherax quadricarinatus grown in pond environments exhibit higher diversity and stability, manifested by an increase in beneficial bacteria abundance and a decrease in opportunistic pathogens. These findings significantly improve understanding of the complex relationship among Cherax quadricarinatus, intestinal microbiota, and the environment. [ABSTRACT FROM AUTHOR]

Modification for operation of semi-quantitative kit was conducted in the present study to build up a quick and quantitative determination method for nitrite concentration in water. For this purpose, an API® Nitrite Test Kit was purchased, after the wavelength and reagent dose were determined spectrophotometrically. Furthermore, standard curve was regressed, the up and down limits were inferred, and the recovery rate and relative deviation were also calculated. Meanwhile, using the chi-square test, the accuracy of the method was estimated, and the interferences of other nitrogen compounds were also analyzed . Results showed that the best wavelength was 540 nm, and the dose of reagent to use was 200 μ,L. The regression equation was significant (P < 0. 01) with a coefficient of 0. 9998 between nitrite concentration and absorbance, and the up and down limits for nitrite determination were 4.32 mg/L and 0. 04 mg/L, respectively. The recovery rate was above 99%, and the relative deviation was 4. 54%. There were no significant differences between determination concentration and actual concentration (P > 0. 05), and the interference of ammonia, nitrate and organic nitrogen were also not significant (P > 0. 05). In conclusion, the method in the present study had a very high accuracy with a narrow deviation, indicating that it could be used as an effective mean for quick and quantitative determination of nitrite concentration. [ABSTRACT FROM AUTHOR]

A 60‐day feeding trial was conducted to investigate the protective effects of dietary α‐lipoic acid (LA) on juvenile abalone Haliotis discus hannai against the oxidative damage under waterborne cadmium (Cd) stress. Three experimental diets were formulated with 0 (Control), 700 (LA‐700) and 2100 (LA‐2100) mg/kg supplement of LA respectively. Each diet was randomly assigned to three replicates of 50 abalones (initial body weight: 3.17 ± 0.01 g), which were exposed to 0.35 mg/L of waterborne Cd. Results showed that abalones' Cd bioaccumulation in the serum, mantle, gill, muscle and hepatopancreas were significantly reduced in LA supplement groups. Besides, in hepatopancreas, the activities of antioxidative enzymes and concentration of glutathione (GSH) in LA supplement group were significantly higher than those in control. Meanwhile, in hepatopancreas, LA‐2100 group showed a significantly decreased malondialdehyde (MDA) concentration and the protein carbonyls in LA supplement groups were significantly lower than those in control. Diets with LA supplementation significantly upregulated the mRNA expression of HdhMTF‐1 (H. discus hannai metal‐responsive transcription factor‐1) and HdhMT (H. discus hannai metallothionein), and elevated metallothionein (MT) concentrations in hepatopancreas. In conclusion, it was suggested that dietary LA could alleviate Cd‐induced oxidative damage through enhancing antioxidative enzyme activities and upregulating the HdhMTF‐1‐mediated HdhMT transcription and synthesis. [ABSTRACT FROM AUTHOR]

Abstract: This study was conducted to investigate protective effects of dietary selenium (Se) on abalone Haliotis discus hannai Ino against the toxicity of cadmium (Cd). A 60‐day feeding trial was conducted with abalone (initial weight: 3.17 ± 0.01 g), which were exposed to 0.34 mg/L of waterborne Cd. During a feeding trial, abalone were fed graded levels of Se at 0.10 (controls), 1.31, and 4.20 mg/kg diet respectively. Results showed that there was no significant difference in specific growth rate and survival rate of abalone among the three treatments. Compared with the controls, dietary Se significantly decreased Cd concentrations in serum, muscle, mantle, gill, mantle, and hepatopancreas of abalone. Besides, compared with the controls, dietary Se significantly increased metallothionein concentration in the hepatopancreas of abalone. Additionally, compared with the controls, dietary Se significantly decreased concentrations of malondiadehyde and protein carbonyl in hepatopancreas of abalone. Meanwhile, compared with the controls, dietary Se significantly increased activities of glutathione peroxidase, thioredoxin reductase, and thioredoxin peroxidase, and concentration of glutathione in the hepatopancreas of abalone. Based on the data above, in abalone, dietary Se showed protective effects against waterborne Cd. [ABSTRACT FROM AUTHOR]

This study was designed to assess the protective effects of dietary selenium (Se) on abalone Haliotis discus hannai Ino against the toxicity of waterborne copper (Cu). A 60-day feeding trial was conducted in a static water system for abalone (initial weight: 3.17 ± 0.01 g) exposed to 0.02 mg L−1 of waterborne Cu. The animals were fed one of the three experimental diets with 0.10, 1.31 and 4.20 mg kg−1 of Se from Na2SeO3·5H2O respectively. Results showed that the abalone fed 1.31 mg kg−1 of dietary Se had the lowest Cu concentration in shell, muscle, mantle, gill, hepatopancreas and serum. Meanwhile, the significant lowest contents of malondiadehyde and protein carbonyl in hepatopancreas were also found in the treatment with 1.31 mg kg−1 of dietary Se ( P < 0.05). In addition, this treatment had significant higher glutathione content and thioredoxin reductase activity in hepatopancreas ( P < 0.05). However, the activity of Se-dependent glutathione peroxidase (Se- GPx) was significantly decreased in the treatment with 4.20 mg kg−1 of dietary Se ( P < 0.05). In this treatment, the protein carbonyl content in hepatopancreas was significantly higher than that in the group with 1.31 mg kg−1 of dietary Se ( P < 0.05). In conclusion, in terms of anti-oxidation and Cu accumulation, the protective effects of dietary Se on abalone against waterborne Cu were dose-dependent. The 1.31 mg kg−1 of dietary Se had this effect, but not 4.20 mg kg−1 of dietary Se. Moreover, the latter increased the oxidative stress in abalone exposed to the waterborne Cu. [ABSTRACT FROM AUTHOR]