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BACKGROUND: Viruses play critical roles in the marine environment because of their interactions with an extremely broad range of potential hosts. Many studies of viruses in seawater have been published, but viruses that inhabit marine animals have been largely neglected. Oysters are keystone species in coastal ecosystems, yet as filter-feeding bivalves with very large roosting numbers and species co-habitation, it is not clear what role they play in marine virus transmission and coastal microbiome regulation. RESULTS: Here, we report a Dataset of Oyster Virome (DOV) that contains 728,784 nonredundant viral operational taxonomic unit contigs (≥ 800 bp) and 3473 high-quality viral genomes, enabling the first comprehensive overview of both DNA and RNA viral communities in the oyster Crassostrea hongkongensis. We discovered tremendous diversity among novel viruses that inhabit this oyster using multiple approaches, including reads recruitment, viral operational taxonomic units, and high-quality virus genomes. Our results show that these viruses are very different from viruses in the oceans or other habitats. In particular, the high diversity of novel circoviruses that we found in the oysters indicates that oysters may be potential hotspots for circoviruses. Notably, the viruses that were enriched in oysters are not random but are well-organized communities that can respond to changes in the health state of the host and the external environment at both compositional and functional levels. CONCLUSIONS: In this study, we generated a first "knowledge landscape" of the oyster virome, which has increased the number of known oyster-related viruses by tens of thousands. Our results suggest that oysters provide a unique habitat that is different from that of seawater, and highlight the importance of filter-feeding bivalves for marine virus exploration as well as their essential but still invisible roles in regulating marine ecosystems. Video Abstract.

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BACKGROUND: Labor-saving pesticide application technology is eagerly pursued in the planting system of Chinese chives. In this study, we developed a set of application approaches by turning fungicides into smoke to achieve this goal. RESULTS: The fungicides fludioxonil, fluopyram, boscalid, procymidone, and prochloraz could be vaporized into smoke at temperatures below 300 °C. The SFR (smoke formation rate) decreased with the increasing temperature. At 300 °C, the SFR of fludioxonil, fluopyram, boscalid and procymidone were all higher than 80%. At 300 °C and 600 °C, there were no significant differences in the smoke particle state of these five fungicides. However, the inhibition rate of these five fungicides against the growth of Botrytis squamosa generally decreased with the temperature. At 600 °C, only fludioxonil and boscalid had inhibition rates higher than 80%. The deposition uniformity of fungicide smoke increased with the increasing amounts of NH4 Cl. When the amount of NH4 Cl reached 80% of the total content, the smoke of fungicide was uniformly deposited throughout each glass slide. In the greenhouse experiment, the control efficacy of fungicide application by smoke was significantly better than that of spraying application, whereas its residue was much lower. CONCLUSION: It is feasible to control air-borne disease through the vaporization of fungicides into smoke by electrical heating. Smoke application would effectively inhibit the spores in the air and would not increase the humidity of the environment. These findings indicate that smoke application is a labor-saving pesticide application technology viable in production. © 2022 Society of Chemical Industry.

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Ammonia nitrogen, a major oxygen-consuming pollutant in the environment, can adversely affect aquatic organisms such as fish, bivalves, and crustaceans. We investigated the toxic effects of ammonia nitrogen on the Hong Kong oyster, Crassostrea hongkongensis, using flow cytometry and 1H nuclear magnetic resonance metabolomics. Exposure to ammonia nitrogen caused time- and concentration-dependent alterations in various immune parameters in hemocytes and impaired the metabolic profiles of the gills. We observed changes in the rate of apoptosis, esterase activity, lysosomal mass, hemocyte counts, phagocytic activity, and mitochondrial mass. Exposure affected metabolic pathways involved in energy metabolism, osmotic balance, and oxidative stress. We concluded that ammonia nitrogen induces metabolic and hematological dysfunction in C. hongkongensis, and our findings provide insights into the biochemical defense strategies of bivalves exposed to acute high-concentration ammonia nitrogen.

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Eighteen novel RNA viruses were found in Crassostrea hongkongensis. Phylogenic analysis shows evidence of recombination between major genes of viruses. Picobirnaviruses are ubiquitous and abundant in oysters.