Abstract
The experiment was conducted in a sealed, temperature-controlled room. The initial water temperature of the treatment group was 12°C, lowered by 1°C a day to 8°C using a chiller, and maintained at that temperature for 3 days. The water temperature was then increased by 1°C per day to 12°C using a heater. The control group were the fish that kept at 12°C at the beginning of the experiment; T1 represents the group that sampled on the first day when the water temperature reached 8 from 12°C; T2 represents the group that sampled when the fish had been kept at 8°C for 3 days; T3 represents the group sampled when the water temperature was increased to 12 from 8°C. The antioxidant abilities of the liver, muscle, and intestine of large yellow croaker at different temperatures and times were determined, and the expression of HSP70 and HSP90 in the liver as well as the changes in intestinal microbiota were investigated. The results showed that the activities of SOD, CAT, GSH-Px, and MDA content increased significantly when the water temperature decreased from 12 to 8°C, significantly higher than those in the control group. The gene expression levels of HSP70 and HSP90 in the liver of large yellow croaker significantly increased under low temperature stress and were significantly higher than those in the control group. The diversity and abundance of intestinal microbiota of large yellow croaker were altered when the water temperature was maintained at 8°C, although the change was not obvious. Proteobacteria, Firmicutes, and Bacteroidetes were the dominate phyla in both the 12 and 8°C groups, and the temperature variation did not change the functional pathways of the microbiota. In conclusion, the acute temperature variation affected the antioxidant ability and heat shock protein expression of large yellow croaker but did not affect the diversity or abundance of the intestinal microbiota. These results will provide a theoretical basis for studying the mechanisms of large yellow croaker overwintering and adaptation to low temperatures.
Highlights
MATERIALS AND METHODSThe large yellow croaker (Larimichthys crocea) is a warm water fish that is one of the most important marine aquaculture species in China
We investigated the effects of temperature on the antioxidant capacity, the expression of heat shock proteins HSP70 and HSP90, and the intestinal microbial community of the large yellow croaker
Our results were consistent with those of previous studies, as superoxide dismutase (SOD), CAT, GSH-PX, and MDA levels in the intestines, liver, and muscles of the large yellow croaker significantly increased when the temperature dropped from 12 to 8◦C. These results indicated that the acclimation of large yellow croaker to low temperature was accompanied by oxidative stress
Summary
The large yellow croaker (Larimichthys crocea) is a warm water fish that is one of the most important marine aquaculture species in China. We investigated the effects of temperature on the antioxidant capacity, the expression of heat shock proteins HSP70 and HSP90, and the intestinal microbial community of the large yellow croaker. The sampled tissues from six fish were mixed together and used as a replicate group to determine enzyme activity and liver HSP expression. The sampling method was as follows: the large yellow croaker was dissected on a sterile table, and the entire intestine were removed (from the stomach to the anus). Microbial DNA was extracted from large yellow croaker intestinal samples using the E.Z.N.A. Soil DNA Kit (50) (Omega Inc., Norcross, United States) following the manufacturer’s instructions. SPSS v19.0 (SPSS Inc., Chicago, United States) was used for all statistical analysis
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