Sub‐chronic exposure to ammonia inhibits the growth of juvenile Wuchang bream (Megalobrama amblycephala) mainly by downregulation of growth hormone/insulin‐like growth factor axis

Abstract

In this study, healthy Wuchang bream (Megalobrama amblycephala) juveniles were exposed to 0, 5, 10, 20 and 30 mg/L total ammonia nitrogen for 30 days to elucidate toxic effects and mechanisms of ammonia on growth performance involved with the regulation of growth hormone/insulin-like growth factor (GH/IGF) and hypothalamic-pituitary-thyroid (HPT) axes. Our results showed that the increasing total ammonia nitrogen concentrations caused dose-depend decreases in the weight gain and specific growth rate but increases in the food conversion ratio and mortality in juvenile bream, indicating growth inhibitory effects induced by ammonia. Concurrently, GH, IGF-1 at protein and mRNA levels were significantly decreased in ammonia exposure groups (p < .05), while serum thyroid stimulating hormone, free thyroxine, free triiodothyronine levels were significantly reduced only in fish exposed to higher concentrations of 20 and 30 mg/L ammonia (p < .05), suggesting that ammonia exposure could perturb both GH/IGF-axis and HPT-axis functions. Furthermore, transcriptional levels of extracellular regulated protein kinases 2 (erk2), phosphatidylinositol 3-kinase (pi3k), protein kinase B (akt), target of rapamycin (tom) and ribosomal protein S6 kinase-polypeptide 1(s6k1) in the dorsal muscle were significantly down-regulated in the fish exposed to ammonia (p < .05). This fact indicated that MAPK/ERK pathway and PI3K/AKT pathway should be responsible for the growth inhibition. Combining the results of spearman correlation coefficient, it should be noted that the GH/IGF axis played a more important role in regulating the growth than the HPT axis in Wuchang bream under persistent ammonia stress.

Adverse effects of chronic ammonia stress on juvenile oriental river prawn (Macrobrachium nipponense) and alteration of glucose and ammonia metabolism

“…The present study showed that chronic ammonia exposure inhibited growth performance and reduced survival rate of juvenile oriental river prawns, similar to results in juvenile Wuchang bream (M. amblycephala) and juvenile yellow catfish. 30,31 However, ammonia did not affect growth performance in channel catfish (Ictalurus punctatus) and Senegalese sole (Solea senegalensis). 32,33 The discrepancy indicated that the tolerance to ammonia in aquatic animals is species specific.…”

Microalgae for nutrient recycling from food waste to aquaculture as feed substitute: a promising pathway to eco‐friendly development

“…Traditional aquaculture, in which fish feces and feed residue could cause water eutrophication, is not regarded as an eco‐friendly model. With the release of ammonia from fish feces and feed residue into the water environment, ammonia toxicity may limit the growth of bream by modulating growth hormone/insulin‐like growth factor and hypothalamic–pituitary–thyroid axes 46 . Also, ammonia stress has negative effects on the antioxidant capacity and livability of aquatic animals 47 .…”

Calmodulin Gene of Blunt Snout Bream (Megalobrama amblycephala): Molecular Characterization and Differential Expression after Aeromonas hydrophila and Cadmium Challenges

“…The blunt snout bream (Megalobrama amblycephala) is a widely distributed and commercially important aquaculture species in China. M. amblycephala is strongly responsive to biotic and abiotic stressors, including Aeromonas hydrophila and Cd, which threatens its culture industry and causes huge economic losses [26,27]. Research into its mechanism of innate immunity to defense pathogens and anti-environment stress is becoming an urgent task that will benefit and improve the immunity of fish in the future.…”