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Nowadays, the cultivation mode of Hyriopsis cumingii urgently needs transformation and upgrading, and realizing sustainable aquaculture lacks the selection of suitable algae and the exploration of culture conditions. This experiment is to evaluate combined effects of ration levels (low ration, medium ration and high ration) and temperature (13.0 ± 0.2°C, 23.0 ± 0.2°C, and 33.0 ± 0.2°C) on immune responses of H. cumingii. Activities of immune enzymes (alkaline phosphatase, superoxide dismutase, catalase and lysozyme) and expression of immune‐related genes (interleukin‐17 and inhibitor of apoptosis protein) in mussels were analysed during 21 days exposure period. Results suggested that the diatom Navicula pelliculosa was suitable algae for H. cumingii, the optimal ration level and temperature of H. cumingii were the medium ration and 23℃. Semi‐starvation, excessive dietary, low‐ or high‐temperature stimulated immune activities, and when beyond the immune regulation range, most immune enzyme activities decreased. Acute stress also stimulated expression of HcIL‐17 and IAP, and long‐term stress of discomfort temperature and ration levels led to immune dysfunction and affected expression of these genes. The study has practical significance in realizing the sustainable aquaculture of H. cumingii and provides a broader perspective regarding the water ecosystem. [ABSTRACT FROM AUTHOR]

Ammonia is one of the major pollutants in the aquatic ecosystem. Hyriopsis cumingii has great potential for the restoration of eutrophic water. However, there is no study investigating the effect of ammonia exposure in H. cumingii. The median lethal concentration (96 h LC50) of unionized ammonium was 12.86 mg/L in H. cumingii. In the study, H. cumingii were exposed to 6.43 mg L−1 unionized ammonium (1/2 96 h LC50) for 0, 6, 12, 24, 48, 72, and 96 h. High environment ammonia induced antioxidant response to protect the body from oxidative damage. After exposure to ammonia, there was a same trend of induction followed by inhibition of the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferases (GST) in the hepatopancreas and gills of H. cumingii. However, the antioxidant response could not completely counteract the oxidation effect during the exposure period, resulting in lipid peroxidation (LPO) and tissue injury in the hepatopancreas and gills of H. cumingii eventually. Moreover, this study indicated that glutamine synthetase (GS), glutamate dehydrogenase (GDH), alanine aminotransaminase (ALT), and aspartate aminotransaminase (AST) in the hepatopancreas and gills may play an important role in ammonia detoxification of H. cumingii. Our results will be helpful to understand the mechanism of aquatic toxicology induced by ammonia in shellfish. [ABSTRACT FROM AUTHOR]

Bacterial disease outbreaks in filter feeder bivalve Hyriopsis cumingii as water contamination become more frequent in the water ecosystem, especially in intensive aquaculture habitats. To characterize host-pathogen interactions between H. cumingii and bacterial infection, we investigated the effects of Stenotrophomonas maltophilia HOP3 and Aeromonas veronii GL1 on the antioxidant response, tissue invasion and transcriptome expression of H. cumingii by infectivity trials. We showed that bacterial infections resulted in tubular necrosis of the hepatopancreas and induced the acute immune response in H. cumingii. The transcriptomic study identified a total of 5957 differentially expressed genes (DEGs) after A. veronii challenge. These DEGs were implicated in 302 KEGG pathways, notably in Apoptosis, Phagosome and Lysosome. The results showed that the relative expressions of all six immune-related DEGs were effectively stimulated with A. veronii , accompanied by tissue differences. Overall, these findings will contribute to an analysis of the immune response of H. cumingii to bacterial infection at the transcriptomic level and its genomic resource for research. • Stenotrophomonas maltophilia and Aeromonas veronii produced hemolysin, caseinase and amylase. • S. maltophilia and A. veronii induced the acute immune response in Hyriopsis cumingii. • 5957 DEGs were identified after A. veronii infection containing 3885 up-regulated and 2072 down-regulated genes determined by RNA-seq. • These DEGs were implicated in 302 KEGG pathways notably in Apoptosis, Phagosome and Lysosome. [ABSTRACT FROM AUTHOR]