Divergent responses in the gut microbiome and liver metabolome to ammonia stress in three freshwater turtles.

Ammonia is a common pollutant in aquaculture system, and toxic to all aquatic animals. However, different aquatic animals exhibit diverse physiological responses to high-level ammonia exposure, potentially indicating their divergent resistance to ammonia stress. In this study, juveniles of three freshwater turtles (Mauremys reevesii, Pseudemys nelsoni and Trachemys scripta elegans) were exposed to different concentrations of ammonia (0, 0.3 and 3.0 mg/L) for 30 days, and their swimming, growth performance, gut microbiota, and hepatic metabolites were measured to evaluate the interspecific difference in physiological responses to ammonia stress. Despite no differences in swimming ability, growth rate, and gut microbial diversity, observable changes in microbial community composition and hepatic metabolite profiles were shown in ammonia-exposed turtles. A relatively higher abundance of potentially pathogenic bacteria was found in M. reevesii than in the other two species. Moreover, microbial compositions and metabolic responses differed significantly among the three species. M. reevesii was, out of the three tested species, the one in which exposure to ammonia had the greatest effect on changes in bacterial genera and hepatic metabolites. Conversely, only a few metabolites were significantly changed in T. scripta elegans. Integrating these findings, we speculated that native M. reevesii should be more vulnerable to ammonia stress compared to the invasive turtle species. Our results plausibly reflected divergent potential resistance to ammonia among these turtles, in view of differential physiological responses to ammonia exposure at environmentally relevant concentrations.

Gut Microbial Composition and Liver Metabolite Changes Induced by Ammonia Stress in Juveniles of an Invasive Freshwater Turtle.

As the most common pollutant in aquaculture systems, the toxic effects of ammonia have been extensively explored in cultured fish, molluscs, and crustaceans, but have rarely been considered in turtle species. In this study, juveniles of the invasive turtle, Trachemys scripta elegans, were exposed to different ammonia levels (0, 0.3, 3.0, and 20.0 mg/L) for 30 days to evaluate the physiological, gut microbiomic, and liver metabolomic responses to ammonia in this turtle species. Except for a relatively low growth rate of turtles exposed to the highest concentration, ammonia exposure had no significant impact on the locomotor ability and gut microbial diversity of turtles. However, the composition of the microbial community could be altered, with some pathogenic bacteria being increased in ammonia-exposed turtles, which might indicate the change in their health status. Furthermore, hepatic metabolite profiles via liquid chromatography-mass spectrometry revealed extensive metabolic perturbations, despite being primarily involved in amino acid biosynthesis and metabolism. Overall, our results show that ammonia exposure causes gut dysbacteriosis and disturbs various metabolic pathways in aquatic turtle species. Considering discrepant defense mechanisms, the toxic impacts of ammonia at environmentally relevant concentrations on physiological performance might be less pronounced in turtles compared with fish and other invertebrates.

Fabrication and evaluation of slow-release lignin-based avermectin nano-delivery system with UV-shielding property.

Nanopesticide is one of the best pesticide formulation technologies to overcome the disadvantages of traditional pesticides, which has received great attention from the international community. Using high-speed emulsification and ultrasonic dispersion technology, an avermectin nano-delivery system (Av-NDs) with a particle size of 80-150 nm was prepared through embedding the pesticide molecule utilizing the cross-linking reaction between sodium lignosulfonate and p-phenylenediamine diazonium salt. The formulation and composition of Av-NDs were optimized, the morphology of Av-NDs was analyzed by scanning electron microscope, transmission electron microscope and dynamic light scattering, and the structure of Av-NDs was characterized by UV, IR and 1H NMR. Anti-photolysis and controlled-release tests show that the stability of Av-NDs is 3-4 times of the original avermectin (Av) and possesses the pH-responsive controlled release property. Furthermore, the insecticidal activity of Av-NDs is better than that of avermectin suspension concentrate (Av-SC). The Av-NDs with anti-photolysis and controlled-release characteristics is suitable for large-scale industrial production and is capable to be utilized as effective insecticide in the field.

Fabrication and evaluation of Lambda-Cyhalothrin nanosuspoemulsion with pH- and temperature-responsive based on polyethylene wax as carrier.

Using polyethylene wax (PW) as the coating matrix, the lambda-cyhalothrin-PW nanosuspoemulsion (LC-PW) with a particle size of 80-150nm was prepared through high-speed stirring, hot melt emulsification and ultrasonic dispersion. The formulation and composition of the LC-PW were optimized, the morphology of the LC-PW was analyzed by dynamic light scattering (DLS) and TEM, and the structure of the LC-PW was characterized by UV and IR. The anti-photolysis test showed that LC-PW had a good anti-photolysis performance. Furthermore, LC-PW could sustainably release Lambda-cyhalothrin, which was pH- and temperature dependent. The insecticidal activity analysis in the greenhouse indicated that the toxic strength between LC-PW and LC-SC (lambda-cyhalothrin-suspension concentrate) to Mythimna separata was similar within the same concentration ranges tested, but the insecticidal duration of LC-PW was significantly longer than LC-SC. Thus, the new type of LC-PW with the properties of anti-photolysis and controlled release is suitable for application in the field as a better insecticide.

Release-controlled microcapsules of thiamethoxam encapsulated in beeswax and their application in field.

Using beeswax as wrapping matrix, two types of release-controlled TM (thiamethoxam)/BK(beeswax-kaolin) microcapsules were prepared by adsorbing TM on kaolin and then encapsulated with beeswax, or directly wrapping TM with beeswax. The structure and morphology of the TM/BK microcapsules were characterized. The effects of different preparation methods, the particle size, pH conditions and different additives on the release property of the TM/BK microcapsules were investigated in water and soil column to compare the advantages of the two approaches. Finally, the insecticidal effect of the TM/BK microcapsules against sugarcane borer and rice planthopper was tested. The results show that the TM/BK microcapsules have a better sustained-release in both water and soil, and the release rate is different under different pH conditions. In addition, the releasing time of the TM/BK microcapsules can be modified by different preparation methods and combination of different additives. In the field applications, the insecticidal activity of the TM/BK microcapsules was better than that of non-sustained control group. Especially in the rice field test, 45 days after the application, the control group lost the activity against rice planthopper because of drug loss, whereas the TM/BK microcapsule group still retained about 90% of the insecticidal activity. The results suggest that the microcapsules have better agricultural application for insect control.