Understanding how white shrimp (Litopenaeus vannamei) tolerate cold temperatures is vital for growth and successful reproduction in specific regions. A new study sheds light on the fascinating mechanisms that allow some shrimp to thrive in cooler waters.
Scientists from the Guangxi Academy of Fishery Sciences (China) analyzed biochemical indicators, cell apoptosis, and metabolomic responses in cold-tolerant (Lv-T) and common (Lv-C) L. vannamei under low-temperature stress (18°C and 10°C).
The Importance of Cold Tolerance
Marine shrimp cannot regulate their body temperature. This makes them particularly sensitive to cold water, which can disrupt their metabolism and lead to death. In this sense, water temperature plays a vital role in shrimp growth and survival.
For L. vannamei, optimal farming temperatures range from 25 to 35°C. Temperatures below 13°C become a danger zone affecting feeding, swimming, and ultimately survival. This sensitivity restricts the shrimp’s geographic range and farming seasons, limiting the economic potential of aquaculture.
The Quest for Cold-Tolerant Shrimp
Understanding how some shrimp thrive in cooler waters is crucial for breeding more cold-tolerant varieties. Some shrimp populations exhibit a surprising capacity to tolerate colder environments.
When faced with temperature changes, shrimp trigger a cascade of biochemical reactions. These reactions affect their metabolism, life cycle, and ultimately their ability to survive in specific environments. Here are some key responses:
- Energy management: Shrimp adjust processes such as glycolysis and gluconeogenesis to maintain energy balance.
- Membrane fluidity: Cells adapt their membranes to maintain proper function at different temperatures.
- Antioxidant defense: Systems are activated to combat harmful reactive oxygen species (ROS) produced under stress.
- Immune regulation: The immune system is modulated to help shrimp fight potential pathogens.
For shrimp farmers cultivating white shrimp in colder areas, ensuring cold tolerance is essential. This study investigates the differences between cold-tolerant (Lv-T) and common (Lv-C) white shrimp when exposed to low temperatures (18°C and 10°C).
Stress Response: Cellular Damage and Biochemical Changes
The research reveals that low temperatures can trigger cell death (apoptosis) in the hepatopancreatic duct, a crucial organ for digestion and metabolism. However, cold-tolerant shrimp (Lv-T) showed a fascinating response:
- Enhanced antioxidant activity: Lv-T shrimp exhibited significantly higher levels of superoxide dismutase (SOD), an enzyme that helps combat harmful molecules produced under stress.
- Altered metabolism: Lv-T shrimp showed elevated triglyceride (TG) levels, a form of energy storage, suggesting adaptations to manage colder environments. Additionally, the study identified changes in other biochemical markers, indicating adjustments in overall metabolism.
Metabolic Analysis: A Deeper Look
Researchers employed a powerful technique called metabolomics to analyze the specific molecules present in shrimp. They found significant differences between Lv-T and Lv-C shrimp, including:
- Increased levels of beneficial metabolites: Lv-T shrimp had higher levels of specific molecules such as LysoPC (involved in fat metabolism) and Pirbuterol (which potentially has antioxidant properties).
- Decreased levels of stress-related metabolites: Conversely, Lv-T shrimp showed lower levels of molecules associated with stress, such as 4-hydroxystachydrine and Oxolan-3-one.
Pathways to Cold Tolerance
By analyzing differentially regulated molecules, the study identified key metabolic pathways potentially involved in cold tolerance. These pathways are linked to functions such as:
- Protein digestion and absorption: Efficient use of proteins may be crucial for Lv-T shrimp to maintain energy levels in cooler waters.
- Central carbon metabolism in cancer: This finding suggests intriguing parallels between adaptations to cold stress and cancer cell survival, prompting further research.
- ABC transporters: These transporters may play a role in Lv-T shrimp by helping to eliminate harmful molecules generated during cold exposure.
Applications for the Shrimp Industry
Understanding the mechanisms behind cold tolerance allows scientists to develop strategies to enhance the cold resistance of farmed shrimp. This could lead to:
- Extended farming seasons: Shrimp farms could operate for longer periods in existing locations.
- New aquaculture regions: Colder climates could become viable for shrimp farming, opening up new markets.
- A more sustainable industry: The geographic expansion of shrimp aquaculture can contribute to food security and economic growth in various regions.
Conclusion: A Multifaceted Mechanism
This study reveals a multifaceted mechanism for cold tolerance in white shrimp. Enhanced antioxidant activity, lipid metabolism adjustments, and the regulation of specific metabolic pathways appear to contribute to the ability of Lv-T shrimp to thrive in cooler environments.
Key findings of the study are:
- Enhanced antioxidant activity: Lv-T shrimp showed significantly higher levels of antioxidant enzymes compared to Lv-C shrimp. These enzymes help combat harmful free radicals produced during cold stress, protecting cells from damage.
- Lipid metabolism advantage: The study also revealed differences in the levels of certain lipid-related metabolites between the two groups of shrimp. Lv-T shrimp exhibited higher levels of these metabolites, suggesting a potential role of lipid metabolism in cold tolerance.
- Hepatopancreatic stress: The research also suggests that cold temperatures damage the hepatopancreatic ducts, a vital organ for digestion and metabolism, in both groups of shrimp. However, Lv-T shrimp may be better equipped to handle this stress.
The study’s findings suggest that cold-tolerant shrimp employ a multipronged approach to survive in cooler waters:
- Stronger antioxidant defenses: Enhanced enzymatic antioxidant activity helps neutralize harmful free radicals.
- Altered lipid metabolism: Specific lipid-related metabolites may play a role in cold tolerance.
The study provides valuable insights for both shrimp producers and researchers. By understanding cold tolerance mechanisms, we can develop strategies to breed more resilient shrimp and optimize aquaculture practices in colder regions.
The study was funded by the National Natural Science Foundation of China, the National Natural Science Foundation of China, Guangxi Science and Technology Major Special Project, and the Modern Agroindustry Technology Research System of China.
Contact
Digang Zeng
Email: zengdigang@126.com
Yongzhen Zhao
Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences
Nanning, 530021, China
Email: yongzhenzhao@hotmail.com
Reference (open access)
Zhu, W., Li, Q., Peng, M., Yang, C., Chen, X., Feng, P., Liu, Q., Zhang, B., Zeng, D., & Zhao, Y. (2024). Biochemical indicators, cell apoptosis, and metabolomic analyses of the low-temperature stress response and cold tolerance mechanisms in Litopenaeus vannamei. Scientific Reports, 14(1), 1-12. https://doi.org/10.1038/s41598-024-65851-2
