Excessive use of antibiotics in aquaculture causes residues in aquatic animal products and harms human health. However, knowledge of florfenicol (FF) toxicology on gut health and microbiota and their resulting relationships in economic freshwater crustaceans is scarce. Here, we first investigated the influence of FF on the intestinal health of Chinese mitten crabs, and then explored the role of bacterial community in FF-induced intestinal antioxidation system and intestinal homeostasis dysbiosis. A total of 120 male crabs (48.5 ± 4.5 g) were experimentally treated in four different concentrations of FF (0, 0.5, 5 and 50 μg/L) for 14 days. Responses of antioxidant defenses and changes of gut microbiota were assessed in the intestine. Results revealed that FF exposure induced significant histological morphology variation. FF exposure also enhanced immune and apoptosis characteristics in the intestine after 7 days. Moreover, antioxidant enzyme catalase activities showed a similar pattern. The intestinal microbiota community was analyzed based on full-length 16S rRNA sequencing. Only the high concentration group showed a marked decrease in microbial diversity and change in its composition after 14 days of exposure. Relative abundance of beneficial genera increased on day 14. These findings illustrate that exposure to FF could cause intestinal dysfunction and gut microbiota dysbiosis in Chinese mitten crabs, which provides new insights into the relationship between gut health and gut microbiota in invertebrates following exposure to persistent antibiotics pollutants.Keywords:florfenicol;gut barrier;apoptosis;gut microbiota;crab
Rampant use of tetracycline in animal feed is a threat to food security, the environment, and human health because of the risk of drug residues. Therefore, it is necessary to establish a sensitive, efficient, and reliable method for qualitative and quantitative detection of tetracycline. In this paper, we synthesized fluorescent carbon dots (FCDs) by thermal cracking of crab shell waste, and obtained a fluorescence quantum yield of 30%. Characterization of the FCDs by transmission electron microscopy, Fourier-transform infrared spectroscopy, ultraviolet visible absorption spectroscopy, and photoluminescence spectroscopy showed that they were fluorescent and evenly distributed with an average size of approximately 10 nm. We designed a sensitive probe for detecting tetracycline using the fluorescence intensity change of the FCDs. This method is sensitive, inexpensive, and environmentally friendly. The concentration of tetracycline was examined by comparing the fluorescence intensities of the FCDs before and after tetracycline addition. The limit of detection for tetracycline was 0.005 mg/L (signal-to-noise ratio = 3), which is promising for method development.
危险品化学品经营许可证（带存储）