A molting chemical cue (N-acetylglucosamine-6-phosphate) contributes to cannibalism of Chinese mitten crab Eriocheir sinensis.

Under high-density culture, cannibalism occurs frequently during the molting of the Chinese mitten crabs Eriocheir sinensis, resulting in a large reduction in production. We found that the leakage of molting fluid from sexually immature crabs informs conspecifics that they are in a molting process. This hypothesis was verified through metabolomics analyses combined with behavioral experiments. The GlcNAc-6-P was identified as a molting biomarker from the differential metabolites by non-targeted metabolomics. In addition, we found that the concentration of GlcNAc-6-P in the molting fluid was significantly higher than other molting metabolites at different molting stages, reaching 5.84 µmol L-1, indicating that the molting fluid was the source of GlcNAc-6-P. Moreover, the behavioral experiments showed that crabs were actively approached to high concentrations of GlcNAc-6-P (1 µmol L-1), but had no obvious choice tendency at different concentrations of UTP, 20-HE and low concentrations of GlcNAc-6-P (0.1 µmol L-1, 0.01 µmol L-1) compared with the control groups. In conclusion, that E. sinensis by sensing the concentration change of GlcNAc-6-P can locate the source of GlcNAc-6-P release and actively approach the high concentration GlcNAc-6-P area and attack the molting crab, causing cannibalism. Blocking the reception pathway of molting chemical cues in E. sinensis, thereby preventing the perception of signals originating from conspecifics' molting in the vicinity, could lead to a reduction in cannibalistic behavior and an increase in overall production. Additionally, this method presents a prospective solution for addressing cannibalism in other crustacean species where such behavior is prevalent.

Nutrient enrichment drives the sediment microbial communities in Chinese mitten crab Eriocheir sinensis culture.

Microbial communities play a critical role in aquaculture ecosystems. To identify the influence of sediment nutrient levels on microbial communities, sediment and water samples were collected from Chinese mitten crab Eriocheir sinensis culture ponds with different nutrient enrichment levels. Relevant physicochemical properties were measured, and 16 S rRNA gene sequencing was applied to identify relevant bacterial communities in the sediments. The results showed that the diversity and composition of microbial communities in sediments with different levels of nutrient enrichment varied considerably. Proteobacteria was the most abundant phylum in all samples, followed by Bacteroidetes, and Desulfobacterota with relative abundances of 23.5-40.9%, 9.8-21.5%, and 9.6-18.1%, respectively. Notably, total nitrogen (TN), organic matter (OM), and pH were important factors driving sediment bacterial community aggregation, the TN concentration explaining 61.5% of the microbial community variation. This study highlights that long-term culture activities alter the degree of sediment nutrient enrichment, which in turn affects microbial community composition and may ultimately have an impact on culture efficiency.

[Impact of Enclosure Culture on Heavy Metal Content in Surface Sediments of Hongze Lake and Ecological Risk Assessment].

In order to explore the concentrations of heavy metals and the influence of fencing on Hongze lake, the content, source, and spatial distribution characteristics of heavy metals in surface sediments and ecological risks were analyzed in 2018 after part of the fence around Hongze Lake was removed. The results showed that the average contents of Cr, Ni, Cu, Zn, As, Cd, and Pb in the surface sediments in Hongze Lake were 66.78, 33.89, 25.35, 74.77, 16.55, 0.23, and 27.20 mg·kg-1, respectively. Cr, Ni, Cu, Zn, and Pb contents were at non-polluting levels, with As and Cd at the lowest level, based on the accumulation index evaluation. Except for Cd, all the elements showed low potential ecological risk. The results showed that the heavy metal content in the fenced, dismantled, and peripheral areas increased and accumulated towards the center of the lake. The removal of the fence did not significantly reduce the heavy metal content in the short-term. Overall, Hongze Lake presented a state of low ecological risk. In the future, environmental policies should include surface sediment accumulation areas and fencing culture in the north and northeast of Hongze Lake.

Pyrrolidone-based polymers capable of reversible iodine capture for reuse in antibacterial applications.

Numerous emerging and re-emerging advanced materials have been successful in capturing iodine pollutants that pose an unprecedented global challenge to public health. However, little attention has been paid to the reutilization of the captured iodine. Herein, we report on a pyrrolidone-based polymer capable of reversible iodine capture for reutilization in antibacterial applications. The pyrrolidone-based polymer poly(N-vinyl-2-pyrrolidone-co-vinyl acetate), denoted as P(VAc-NVP), was synthesized facilely via a one-step radical copolymerization strategy, and the synthesis was regulated by step-by-step optimization, specifically by tuning the feed ratio of NVP to VAc. The as-synthesized P(VAc-NVP) copolymer functioned as an adsorbent for iodine in various solutions, including water/ethanol, cyclohexane, and petroleum ether, in addition to having the special capability of releasing iodine in the presence of starch or bacteria. This opens up a new horizon for its functional practical use as a flexible adsorbent to capture iodine for safe disposal. Interestingly, the P(VAc-NVP) copolymer, after adsorbing iodine, showed antibacterial ability against pathogenic bacteria, including Staphylococcus aureus and Escherichia coli, when a series of simulated and practical antibacterial assays were conducted. It is believed that this proposed strategy based on the synergism of iodine capture and antibacterial use should have great potential for environmental remediation and public healthcare.