One of the challenges faced by shrimp producers is the presence of ammonia, a prevalent contaminant in aquaculture systems, which poses a risk to the health of these crustaceans.
The shrimp’s intestine plays a crucial role in its immunity and metabolism, making it essential to understand how ammonia-induced stress can impact intestinal health and, ultimately, shrimp survival.
Researchers from the Chinese Academy of Fishery Sciences and the Sanya Tropical Fisheries Research Institute exposed Litopenaeus vannamei shrimp to ammonia levels of 2 mg/L for 7 days to analyze alterations in intestinal tissue morphology, immune status, microbial community, and metabolic function.
The findings shed light on the detrimental effects of ammonia stress on shrimp intestinal health, which, in turn, affects their survival.
The importance of the Intestine for Shrimp
In recent years, shrimp intestinal diseases, including enteritis, white feces syndrome (WFS), and Enterocytozoon hepatopenaei (EHP) infection, have become increasingly prominent.
The shrimp’s intestine serves as a vital organ for nutritional metabolism and immune defense. Thus, shrimp intestinal health has garnered significant attention.
Effects of Ammonia Stress on Intestinal Health
Several studies have reported that in shrimp aquaculture, ammonia-N content in ponds can exceed 2-3 mg/L and can reach levels as high as 46 mg/L in intensive practices. Even in biofloc systems, ammonia-N concentration remains as high as 1 mg/L.
Ammonia stress had a significant impact on the health of Litopenaeus vannamei shrimp. During the study, several changes were observed in the intestines of shrimp exposed to 2 mg/L ammonia-N, including:
- Decreased Survival: Shrimp exposed to ammonia stress exhibited reduced survival rates, underscoring the severity of the issue.
- Intestinal Mucosal Damage: Ammonia stress led to damage to the intestinal mucosa and exfoliation of epithelial cells.
- Changes in Gene Expression: An increase in relative gene expression levels related to oxidative stress (Nrf2 and SOD) was observed, along with a decrease in GPx levels.
- Inflammation and Apoptosis: Ammonia stress triggered the overexpression of genes associated with endoplasmic reticulum stress, inflammatory cytokines, and apoptosis mediators.
Changes in Microbial Community and Metabolic Impact
In addition to effects on intestinal health and immunity, ammonia stress also had an impact on the shrimp’s microbial community and metabolic function. The following consequences were observed:
- Changes in Microbial Diversity: Ammonia stress reduced microbial diversity in the shrimp’s intestines.
- Variations in Bacterial Community Composition: Significant changes were identified in the bacterial community composition, including the presence of bacteria such as Bacteroides, Enterococcus, Faecalibacterium, Nautella, Pseudoalteromonas, Tenacibaculum, and Weissella.
- Disruption in Metabolic Function: Notable changes were observed in metabolic function, affecting pyrimidine, purine, amino acid, and alkaloid metabolism.
Conclusions
This study emphasizes the importance of addressing ammonia stress in shrimp farming, as it can have detrimental effects on intestinal health, immunity, the microbiota, and metabolic function.
“The study revealed that 2 mg/L ammonia-N stress damaged shrimp intestinal health by harming mucosal integrity, interfering with immune homeostasis, causing microbial community and metabolic variation, which are related to the decreased survival of the shrimp and should be paid attention to in shrimp farming,” the researchers concluded.
The decrease in shrimp survival when exposed to significant levels of ammonia-N is a concern that requires attention in the shrimp industry.
To ensure a sustainable future in shrimp farming, practices and technologies must be implemented to reduce ammonia exposure and mitigate its harmful effects on the health of these crustaceans.
Research in this area is essential to better understand underlying mechanisms and develop effective strategies for managing and preventing ammonia stress in Litopenaeus vannamei shrimp aquaculture.
The study was funded by the Key-Area Research and Development Program of Guangdong Province, the Central Public-Interest Scientific Institution Basal Research Fund, the South China Sea Fisheries Research Institute, CAFS, the Agricultural Research Outstanding Talents Training Program, and the Hainan Provincial Natural Science Foundation of China.
Contact
Yafei Duan
Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences
Guangzhou, 510300, PR China.
Email: duanyafei89@163.com
Reference
Yafei Duan, Yuxiu Nan, Xuanyi Zhu, Yukai Yang, Yifu Xing. 2023. The adverse impacts of ammonia stress on the homeostasis of intestinal health in Pacific white shrimp (Litopenaeus vannamei), Environmental Pollution, 2023, 122762, ISSN 0269-7491, https://doi.org/10.1016/j.envpol.2023.122762.
