ABSTRACT: Water renewal intensity is an important factor in environmental regulation in intensive aquaculture systems, yet the long-term effects of different daily water exchange rates on growth performance and intestinal molecular responses in economically important gastropods remain poorly understood. In this study, the ivory shell, Babylonia areolata, was used as the experimental species, with a 100% daily water exchange group (H group) and a 50% daily water exchange group (L group) established for a 6-month culture trial. Growth-related traits and intestinal transcriptomic profiles were jointly analyzed to evaluate the responses of B. areolata to different water renewal intensities. At the end of the experiment, no significant differences were detected between the two groups in final body weight, weight gain, or survival rate (P > 0.05). Based on 16 intestinal RNA-Seq libraries, a total of 657,244,736 raw reads and 97.01 Gb of clean data were obtained, with Q30 values ranging from 95.84% to 96.22% and mapping rates to the reference genome ranging from 84.88% to 89.99%. A total of 820 differentially expressed genes were identified between the H and L groups, of which 370 genes showed higher expression in the H group and 450 genes showed higher expression in the L group. GO and KEGG enrichment analyses showed that the differentially expressed genes were mainly involved in innate immunity and stress responses, amino acid and related small-molecule metabolism, and signal regulation. GSEA further revealed enrichment of gene sets associated with ubiquitin-related processes, endopeptidase inhibitor activity, regulation of cell death, and the biosynthesis of amino acids, organic acids, and small molecules. The expression trends of five candidate genes determined by qRT-PCR were generally consistent with the RNA-Seq results, with two genes showing significant differences. Overall, 50% and 100% daily water exchange rates did not result in significant divergence in growth or survival phenotypes of B. areolata under the present experimental conditions, but induced selective transcriptional regulation related to intestinal immune stress, metabolism, and cellular homeostasis.
