Ivory shell (Babylonia areolata) is a commercially important aquaculture species mainly found on the southeast coast of China. However, it has been greatly affected by vibriosis in recent years. In this study, FP17 (a potential pathogen) was isolated from a dying ivory shell with “acute death syndrome” and confirmed as a pathogen via infectious experiment. Furthermore, phylogenetic analysis based on the average nucleotide identity (ANI) sequencing of the 16S rRNA gene and housekeeping genes (ftsz, gapA, gyrB, mreB, pyrH, rpoA, and topA) indicated that FP17 was identical to Vibrio tubiashii. Transmission electron microscopy showed that FP17 is curved and has a short rod shape, with a single flagellum. Besides, the calculated LD₅₀ after the intramuscular injection of FP17 was 2.11 × 10⁶ CFU/g at 14 d. The genome of the FP17 strain consists of two chromosomes and one plasmid with 5,261,336 bp and 45.08% GC content, including 4824 open reading frames (ORFs) and 150 non-coding RNAs (ncRNA). Genome mining revealed that 120 candidate gene clusters, including vibrioferrin and flagellum-related proteins, are responsible for virulence. Comparative genomic analysis showed that vibrioferrin genes, such as pvs and type Ⅵ secretion system protein genes (vas), are specific in V. tubiashii FP17 but not in the ATCC19109 strain. Furthermore, 92 antimicrobial resistance (AMR) genes, such as tufA, tet(35), crp, etc., were mapped within the genome as the potential candidate for virulence, consistent with antibiotic susceptibility assay. This is the first study to describe the complete genome sequence of V. tubiashii infecting ivory shell. The genetic characteristics, virulence factors, and antimicrobial resistance of the V. tubiashii strain FP17 were also explored.

We report the complete genome sequence of Photobacterium damselae subsp. damselae strain HNDF01, isolated from diseased Plectropomus leopardus in Hainan, China. The genome consists of two circular chromosomes (4,174,829 bp) and one plasmid (160,669 bp), encoding 3,753 protein-coding genes, 217 tRNAs, 47 rRNAs, and 10 sRNAs.

Vibrio tubiashii infection has led to several Babylonia areolata pandemics on the southeast coast of China, yet the immune response of the ivory shell against V. tubiashii and the specific pathogen–host interaction remain unclear. This dynamic study aimed to characterize the response of B. areolata to V. tubiashii infection with the use of pathology, transcriptomics, an enzymatic assay, and inflammatory cytokines. Hepatopancreatic cells showed marked vacuolar degeneration with intact cell membrane and extensive cytoplasmic vacuolization after infection. The dynamic transcriptome of the hepatopancreatic tissue was analyzed by RNA-seq after V. tubiashii infection, and a total of 2733 (3 h), 5610 (24 h), 3323 (48 h), and 418 (72 h) differentially expressed genes (DEGs) were identified during infection. The GO and KEGG analyses showed that the DEGs were enriched in metabolic regulation, lysosome, and multiple immune-related pathways such as the MAPK signaling pathway. The immune response of B. areolata was distinct, where the early stage of immune response (3 h) showed binding, focal adhesion, and apoptosis, as well as an activated antioxidant system. Here, expression of TNF-α, IL-1, and IL-8 was significantly increased in the hepatopancreas, whereas expression of IL-6 and IL-17 increased afterward. During the middle stage (24 h and 48 h), a large number of DEGs were suppressed, especially those associated with metabolism and lysosomes, although their expression returned to normal during prolonged infection (72 h). The PPI network showed that ppp2, atp6, and sos1 were the top immune-related DEGs during infection. Key infection-related and time-course-related genes were analyzed by WGCNA. This study illustrates that oxidative stress, inflammation, and apoptosis are strategies of the hepatopancreatic immune response in B. areolata against V. tubiashii infection and enlightens conservation and production by furthering our understanding of gastropod immunity.

In aquaculture, reduced water exchange helps constrain exogenous pathogen invasion, lower pumping costs, and improve management efficiency; nevertheless, its effects on the growth of cultured aquatic animals remain poorly characterized. This study compared two daily water-exchange rates (100% and 0%) to evaluate growth and associated intestinal responses in Babylonia areolata (ivory shell). Growth performance and intestinal enzyme activities were measured, while 16S rRNA gene sequencing and untargeted metabolomics were used to characterize microbial composition and metabolite profiles. The low-water-exchange group exhibited significantly lower weight gain rate (WGR, p < 0.0001), specific growth rate (SGR, p < 0.0001), daily increments in shell length (DISL, p = 0.0060), and shell width (DISW, p = 0.0012). Intestinal total superoxide dismutase (T-SOD, p < 0.0001) and lipase (LIP, p = 0.0011) activities were also significantly lower. The relative abundances of Vibrio, Halodesulfovibrio, and Fusibacter were higher, whereas that of Christensenellaceae_R-7_group was lower. Lipid-related metabolic pathways showed the most pronounced intestinal differences. Intestinal levels of prostaglandins (PGs), leukotrienes (LTs), and sphingosine (Sph) were significantly higher under low-water-exchange conditions. The relative abundance of Halodesulfovibrio correlated positively with PGs and LTs but negatively with lysophospholipids (Lpc) and T-SOD activity. The relative abundance of Christensenellaceae_R-7_group correlated positively with LIP activity and was significantly associated with metabolites involved in primary bile acid biosynthesis. Overall, low-water-exchange conditions were associated with coordinated changes in growth, intestinal enzyme activities, microbial composition, and metabolite profiles, although the underlying mechanisms require functional validation. These findings provide new insights into intestinal microbiota–metabolite responses to low-water-exchange conditions and may guide future validation and intervention studies in RAS-based ivory shell culture.