Transcriptomic analyses of the acute aerial and ammonia stress response in the gill and liver of large-scale loach (Paramisgurnus dabryanus).

The large-scale loach (Paramisgurnus dabryanus) is one of the most commercially important cultured species. Ammonia nitrogen accumulation is one of the key issue which limited production and animal health in aquaculture, but few of information is available on the molecular mechanisms of ammonia detoxification. We performed transcriptomic analyses of the gill and liver of large-scale loach subjected to 48 h of aerial and ammonia exposure. We obtained 47,473,424 to 56,791,496 clean reads from the aerial exposure, ammonia exposure and control groups, assembled and clustered a total of 92,658 unigenes with an average length of 909 bp and N50 of 1787 bp. Totals of 489/145 and 424/140 differentially expressed genes (DEGs) were detected in gill/liver of large-scale loach after aerial and ammonia exposure through comparative transcriptome analyses, respectively. In addition, totals of 43 gene ontology (GO) terms and 266 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were identified. After aerial and ammonia exposure, amino acid metabolism pathways in liver of large-scale loach were significantly enriched, suggesting that large-scale loach responded to high exogenous and endogenous ammonia stress by enhancing amino acid metabolism. Besides, the expression of several ammonia transporters (i.e., Rhesus glycoproteins and Aquaporins) in gill of large-scale loach were markedly changed after 48 h of aerial exposure, suggesting that large-scale loach responded to high endogenous ammonia stress by regulating the expression of Rh glycoproteins and Aqps related genes in gill. The results provide valuable information on the molecular mechanism of ammonia detoxification of large-scale loach to endogenous and environmental ammonia loading, will facilitate the molecular assisted breeding of ammonia resistant varieties, and will offer beneficial efforts for establishing an environmental-friendly and sustainable aquaculture industry.

High concentrations of environmental ammonia induced changes in large-scale loach (Paramisgurnus dabryanus) immunity.

High concentrations of environmental ammonia can cause reduced immunity and death in fish, causing enormous economic losses. Air-breathing fish usually have a high ammonia tolerance and are very suitable for high-density fish farming. However, research on the effects of environmental ammonia on air-breathing fish immunity is lacking. Therefore, this study investigated the effects of environmental ammonia on the immunity of large-scale loach (Paramisgurnus dabryanus) by exposing fish to 30 mmol/L NH4Cl solution and subsequently analyzing the changes in serum and liver immune indicators, including total protein, albumin, globulin, immunoglobulin (Ig) M, lysozyme, complement component (C) 3 and C4, heat shock protein (HSP) 70, HSP90, tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-6, and IL-12. Results revealed that ammonia exposure significantly affected the total protein, albumin, globulin, IgM, complement C3 and C4, HSP70, HSP90, and inflammatory cytokine contents in the body, indicating that ammonia exposure induced a significant immune response and lowered bodily immunity. However, most of the immune indicators significantly decreased in the later stages of the experiment, suggesting a weakened immune response, which may be due to the species-specific ammonia detoxification ability of large-scale loach that reduces ammonia toxicity in the body.