Fasting-induced changes in non-specific immunity of crucian carp (Carassius auratus) is related to gut microbiota. fish environmental sample

Due to environment changes, many animals can often be affected by fasting, which likely present significant challenges to gut microorganisms. Gut microbiota play important roles in fish immunity, nutrition and the adaptation to environmental changes. We comprehensively characterized the effects of fasting on gut microbial diversity, growth performance and host non-specific immunity in C. auratus, as few studies have focused on the interactions among them. Short term fasting could enhance the anti-oxidant capacity and pathogen resistance, while, long term fasting lead to the depressed non-specific immunity. And the relative gut lengths were particularly higher in the group F. The bacterial communities were separated into four clusters based on different degree of fasting. Short term fasting resulted in increased alpha diversity and ecosystem stability of gut microbiota. A higher relative abundance of Bacteroides, Akkermansia and Erysipelotrichaceae was observed in short term fasted fishes. Some members of these fermentative bacteria were positively correlated with anti-oxidant capacity, pathogen resistance and whole/relative gut length. Enterobacteriaceae, dominant in control group, were positively correlated with LBP. Long term fasted fishes harbored abundant intestinal opportunistic pathogens (Vibrio and Vibrionaceae). These results highlighted the surge of some potential beneficial bacteria or opportunistic pathogens as bacterial signatures that were associated with innate immune in C. auratus during different degree of fasting.