In this study, we investigated the effects of caloric restriction (CR) on growth, gene expression, and gut microbiota in Hippocampus erectus, and explored the possibility of a rejuvenating effect by comparing CR and ad libitum (AL) seahorses with young (CY) or old seahorses (CO). For the study three-month-old seahorses were subjected to either AL or intermittent fasting diets over 5 months, inducing CR due to their lack of a stomach. Total mRNA sequencing of liver, head kidney, and gonads was conducted on 40 individuals (10 AL, 10 CR, 10 CY, CO, including males and females), making a total of 120 samples.