Effects of intermittent fasting on behavioral and physiological stress indicators in Pacific abalone during persistent ocean heat waves

Abstract

Global climate change has increased the frequency of marine heat waves, posing a continuous threat to the survival of economically relevant shellfish species. This, in turn, affects the stability of ecological systems and the security of the aquaculture industry. In this study, we investigated the effects of different fasting regimens (GY: fasting at 1-day intervals, GL: fasting at 2-day intervals) on the behavioral and physiological adaptability of Pacific abalone (Haliotis discus hannai), a marine gastropod, particularly in response to recurrent marine heat waves. Our findings revealed that the survival rates of abalone in both the GY and GL groups were significantly higher than those in the unfasted control group (ZC) (P < 0.05). Furthermore, behavioral assessments revealed that the cumulative distance moved, feeding durations, and the percentage of cumulative feeding time relative to movement time were significantly greater in the GL group compared to both the ZC and GY groups (P < 0.05). Sequencing of the 16S rDNA amplicon revealed that the intestinal microbial community of abalone in the GL group harbored a higher abundance of beneficial bacteria (Arenimonas, Pseudolabrys) compared to the GY and ZC groups. In contrast, the potentially harmful bacterium Tenacibaculum was significantly reduced in the GY group relative to the ZC group (P < 0.05). A non-targeted metabolomics analysis identified amino acids and fatty acids, such as Citrulline, Leu-Pro, and L-Glutamate, as differential metabolic markers. KEGG enrichment analysis indicated that the ‘Biosynthesis of amino acids’ pathway was significantly enriched in both the GY and GL groups compared to the ZC group (P < 0.05). Further analysis of 23 amino acids showed that 15 and 20 amino acids, including glycine and serine, were downregulated in the GY and GL groups, respectively, compared to the ZC group. Pearson correlation analysis revealed a positive correlation between the relative abundance of both Arenimonas and Pseudolabrys in the abalone's gut and citrulline content in the GY and GL groups (P < 0.05). These findings suggest that intermittent fasting not only promotes energy redistribution, serving as an effective strategy for abalone to cope with oceanic heat waves, but also provides valuable insights into the behavioral and physiological plasticity of marine shellfish in response to global climate change.