Effects of feeding frequency on juvenile Chinese sturgeon Acipenser sinensis

Selection, identification and evaluation of optimal reference genes in Chinese sturgeon (Acipenser sinensis) under polypropylene microplastics stress

Polypropylene microplastics (PP-MPs) are emerging environmental contaminants that have the potential to cause adverse effects on aquatic organisms. Reverse transcriptase quantitative real-time polymerase chain reaction (RT-qPCR) is a valuable tool for assessing the gene expression profiles under PP-MPs stress. To obtain an accurate gene expression profile of tissue inflammation and apoptosis that reflects the molecular mechanisms underlying the impact of PP-MPs on Chinese sturgeon, identifying reliable reference genes is crucial for RT-qPCR analysis. In this study, we constructed an experiment model of Chinese sturgeon exposed to PP-MPs, assessed the pathological injury, metabolic profile responses and oxidative stress in liver, evaluated the reliability of 8 reliable reference genes by 4 commonly used algorithms including GeNorm, NormFinder, BeatKeeper, Delta Ct, and then analyzed the performance of inflammatory response genes in liver, spleen and kidney with the best reference gene. HE staining revealed that the cytoplasm full small vacuoles and nucleus diameter increased were occurred in the liver cell of PP-MPs in treatment groups. Additionally, oxidative and biochemical parameters were significantly changes in the liver of treatment groups. For the reference genes in PP-MPs exposure experiments, this study screening the optimal reference genes including: EF1α and GAPDH for liver and spleen, and GAPDH and RPS18 for kidney. Besides, 2 inflammatory response genes (NLRP3, TNF-α) were chosen to assess the optimal reference genes using the least stable reference gene (TUB) as a control, verified the practicality of the select reference genes in different tissues. We also found that the low concentration of PP-MPs could induce the liver tissue damage and inflammatory response in Chinese sturgeon. Our study initially evaluated the impact of short-time exposure with PP-MPs in Chinese sturgeon and provided 3 sets of validated optimal reference genes in Chinese sturgeon exposure to PP-MPs.

Influence of stocking density and environmental factors on the expression of insulin-like growth factors in cage-reared butter catfish (Ompok bimaculatus, Bloch 1794) within a large reservoir ecosystem

In vertebrates, insulin-like growth like factors (IGFs) play an important role in growth and other physiological processes. The GH-IGF axis is considered a valuable tool to monitor fish growth performance. Herein, we report the molecular characterization of igf-1, igf-2, and β-actin transcripts and relative expression of igf-1 and igf-2 in the liver and muscle tissue of cage-reared butter catfish, Ompok bimaculatus, in response to different stocking densities (T1, 15 fingerlings m-3; T2, 25 fingerlings m-3; and T3, 35 fingerlings m-3) over 180 days of culture duration. The length of the partial amplified transcript sequence of Obigf-1, Obigf-2, and Obβ-actin was 325, 438, and 924 bp, respectively. Phylogenetically, Obigf-1 and Obigf-2 were closely clustered with catfishes, viz., Clarias magur, Bagarius yarrelli, and Silurus asotus. The expression of igf-1 was significantly downregulated in the liver at higher densities after 120 days as biomass in the cages increased, while igf-2 expression did not change with the stocking densities over the culture period. Cortisol concentration was significantly elevated in T3 groups post 150 days of the culture period and correlated negatively with the expression of igf-1 (p < 0.05) and igf-2 (p > 0.05). Environmental parameters, pH, TDS, hardness, conductivity, and alkalinity showed a significant positive correlation with hepatic IGF expression. Our study indicates that the liver-derived igf-1 plays a more important role in the regulation of growth in response to culture density in the species studied, and thus, igf-1 can be used effectively as a biomarker for growth. Furthermore, this study will help in planning a proper harvest schedule and optimize the culture practices of O. bimaculatus in an open water cage system.

Seasonal Changes of Growth, Immune Parameters and Liver Function in Wild Chinese Sturgeons Under Indoor Conditions: Implication for Artificial Rearing

Seasonality has a significant effect on the physiology of fish, especially the effect of water temperature changes. In the present study, the growth, innate immune parameters and liver function indices of two rescued wild adult Chinese sturgeons under captive conditions were monitored for 1 year. The results showed that the total annual weight loss rate of the male was −4.58% and the total weight gain rate of the female was 24.12%, in which the weight of both individuals registered highly significant differences in summer, fall and winter (p < 0.01). The male Chinese sturgeon also exhibited negative specific growth rates (−0.1 to −0.8%) during spring to fall, whereas positive specific growth rates, ranging from 0.03 to 0.11%, were recorded in the female. Seasonality also affected the innate immune parameters of the two Chinese sturgeons, in which leukocytes had been increasing since spring and C-reactive protein (CRP) content was significantly higher (p < 0.05) in summer than fall in both individuals. The CRP level of the male Chinese sturgeon showed a significant increase from fall to winter (p < 0.05), suggesting that it may have contracted infection or inflammation during this study period. With the analysis of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), transaminase (AST:ALT) ratio, alkaline phosphatase, albumin to globulin ratio and triglycerides, it was found that the liver function of the captive Chinese sturgeons was adversely affected along seasonal changes, with the highest degree of liver impairment in winter. In combining observations from growth performance and changes in innate immune and liver function parameters, the present findings deduced that the male Chinese sturgeon under study was more susceptible to seasonal changes than the female. For better indoor culture of adult Chinese sturgeons, monitoring of hematological parameters to detect early signs of inflammation and liver function abnormality should be conducted with routine veterinary care during prolonged captivity.