Physiological Responses of Pacific White Shrimp Litopenaeus vannamei to Temperature Fluctuation in Low-Salinity Water.

Temperature is a significant environmental factor in aquaculture. To investigate the physiological responses during temperature fluctuation (28~13°C), experimental shrimps (Litopenaeus vannamei) were treated with gradual cooling from acclimation temperature (AT, 28°C) to 13°C with a cooling rate of 7.5°C/day and rose back to 28°C at the same rate after 13°C for 24 h. Hepatopancreas histological changes, plasma metabolites concentrations, relative mRNA expression of unfolded protein response (UPR) pathway and apoptosis in hepatopancreas and hemocyte were investigated. The results showed that with the decline of temperature, the number and volume of the secretory cells in hepatopancreas increased significantly, the tubule lumen appeared dilatated, and the epithelial cell layer became thinner. The contents of glucose (Glu) significantly decreased to the minimum value of 13°C for 24 h. The contents of triglyceride (TG), total cholesterol (TC), and total protein (TP) increased and reached the peak of 13°C for 24 h. Alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities in plasma reached the lowest and highest value in 13°C, respectively. The expressions of all genes related to UPR and apoptosis in the hepatopancreas and hemocytes were significantly changed during the cooling process and reached the highest level of 13 and 13°C for 24 h, respectively. During re-warming stage, the histopathological symptoms got remission and each of the plasma metabolite concentrations and gene expressions returned to AT levels. These results revealed that pacific white shrimp can adapt to a certain level of temperature fluctuation by self-regulation.

Investigating the physiological responses of Pacific white shrimp Litopenaeus vannamei to acute cold-stress.

BACKGROUND: Litopenaeus vannamei is one of the most important aquaculture shrimps in the world and low temperatures present a serious challenge to its survival, growth, and distribution. METHODS: To investigate their physiological responses during acute cold-stress, L. vannamei were treated under acute cooling conditions from 28 to 13 °C with a cooling rate of 2.5 °C/2 h and were maintained at 13 °C for 12 h. Plasma metabolite concentrations, histological changes, and relative gene expression related to the unfolded protein response (UPR) pathway and apoptosis in the hepatopancreas and the hemocytes of L. vannamei were investigated. RESULTS: The results revealed that the concentrations of triglycerides, total cholesterol, and total protein in plasma reached their peaks at 23 °C, and then decreased to their minimum values at 13 °C for 12 h. The activity of alkaline phosphatase in the plasma decreased to its lowest level while the activity of alanine aminotransferase increased to its highest level at 13 °C for 12 h. The hepatic tubules became necrotic and the basement membranes were ruptured at 13 °C for 12 h. The gene expression related to UPR and apoptosis in the hepatopancreas and hemocytes was significantly altered by the decrease in the temperature. DISCUSSION: The results revealed that acute cold-stress caused histological damage in the hepatopancreas of L. vannamei, reducing its immunity. The three UPR pathways were involved in the process of acute cold-stress and the response of activating transcription factor 6 to UPR may be faster and more directthan the IRE1 and PERK pathways.

Microbiota comparison of Pacific white shrimp intestine and sediment at freshwater and marine cultured environment.

Environmental microbiota plays important roles in the intestinal microbiota of aquatic animals. The Pacific white shrimp with high commercial value and euryhaline property has become the most important commercial species of shrimp in the world. However, the association between shrimp intestine and sediment at freshwater and marine cultured environment should be investigated to reveal the microbiota differences. In the present study, Miseq sequencing technology and bioinformatics were used to comprehensively compare the bacterial communities and all samples' V3-V4 regions of 16S rRNA gene were sequenced. Results showed that 55 phyla and 789 genera were identified due to the classifiable sequence. Sequencing data demonstrated statistically significant diverse microbiota compositions in the shrimp intestine and sediment at freshwater and marine cultured environment at the phylum and genus level. At the phylum level, the dominant phyla in all groups were Proteobacteria, Chloroflexi, Actinobacteria, Firmicutes, Cyanobacteria, Bacteroidetes, Acidobacteria, Verrucomicrobia, Saccharibacteria. Proteobacteria were the most abundant and largest phylum except in the intestine of marine cultured shrimp and Actinobacteria may be enriched in the shrimp intestine from sediment. At the genus level, nine out of the twelve dominant genera exhibited statistically significant differences among all groups. Moreover, Lactobacillus tend to be enriched in the freshwater cultured shrimp intestine, while Synechococcus and Vibrio extremely abundance in the marine cultured shrimp intestine. These results showed that the bacterial compositions are mostly the same in shrimp intestine and sediment, while with different relative abundances of the bacterial communities. In conclusion, this study may greatly enhance our understanding of the microbiota characteristics between shrimp and sediment. Moreover, it provided guidance for the healthy aquaculture at freshwater and marine cultured environment.

Effects of gelsemine on oxidative stress and DNA damage responses of Tetrahymena thermophila.

Gelsemine is an important toxic substance extracted from Gelsemium elegans, which has a lot of biological functions in cells and organisms, but its toxicity has been rarely reported in Tetrahymena thermophila. In this study, we used the protozoan T. thermophila as an experimental model to investigate the potential toxicity-induced mechanism of gelsemine in the unicellular eukaryote. Our results clearly showed gelsemine inhibited T. thermophila growth in a dose-dependent manner. This exposure also resulted in oxidative stress on T. thermophila cells and antioxidant enzyme levels were significantly altered at high gelsemine levels (p < 0.05). Gelsemine produced a slight apoptotic effect at the highest (0.8 mg/mL) gelsemine level used here (p < 0.05). Furthermore, the toxin-induced DNA damage in a dose-dependent manner. The ultrastructural analysis also revealed mitophagic vacuoles at 0.4 and 0.8 mg/mL levels of gelsemine exposure. Moreover, expressions of oxidative stress-related and MAP kinase genes were significantly changed after exposure to 0.8 mg/mL level of gelsemine (p < 0.05). Altogether, our results clearly show that gelsemine from G. elegans can inhibit the growth via inducing oxidative stress and DNA damage in T. thermophila cells.