Physiological adaptation and gut microbiota changes of orange mud crab Scylla olivacea in response to increased temperature condition

High emissions of greenhouse gases to the atmosphere via human activities have caused climate change and ocean warming. The rising water temperature is an abiotic factor that may negatively affect various biological and physiological processes of aquatic organisms, such as growth, digestion, immunity, and survival. Orange mud crab (Scylla olivacea) are commercially important crustacean species of coastal countries along the Indo-Pacific region. Their predominant habitat—the coastal zones make—them vulnerable to ocean warming. This study aimed to understand the impact of temperature increase on the physiology and gut microbial alteration of S. olivacea. Adults of S. olivacea were subjected to present-day water temperature and warming scenarios (∆T =  + 4 °C) for 14 days. Growth (weight gain and specific growth rate), oxygen consumption, and serotonin levels of S. olivacea showed a significant increase under warming scenario. However, exposure to higher temperatures did not induce higher feed consumption, feed conversion rate, hepatosomatic index, and hemolymph glucose level in S. olivacea. The thermal coefficient was 3.5232 on day 7 and decreased to 1.2534 on day 15. Furthermore, Vibrio species bacteria were more abundant in the intestines of S. olivacea under warming scenario. These results suggest that S. olivacea exposed to the warming scenario may positively impact the aquaculture industry (higher weight gain), but also bring risk of disease outbreak caused by Vibrio spp. Further studies are needed to better understand the long-term effect of warming scenario on the growth and health of coastal crustacean species, especially species being threatened by fishing pressure.