National Sun-Yat sen University, Taiwan
Title: The isolated and combined influences of ammonia and nitrite on phenoloxidase system of white shrimp (Litopenaeus vannamei)
The research topic of our lab focus on aquaculture physiology, especially molecular stress responses. Stress is an unavoidable component of the animals in aquaculture environment. Aquaculture species under intensive culture conditions are usually exposed to diverse environmental stressors. Environmental stress would cause adverse effects on physiological regulation, including immunity. Therefore, the water quality of aquaculture pond is tightly correlated to the fitness of cultivated animals. The major goal of our research is to adopt science-based research and practices for establishing appropriate criteria for water quality management of aquaculture ponds to reduce and minimize stress and avoid the occurrence of severely harmful effects at population level.
Aquatic animals would naturally or anthropogenically face to environmental stress leading to many physiological disturbances, including interference in immune response. The shrimp Litopenaeus vannamei is an economically important species worldwide. Intensive farming with recirculating system is the common aquaculture practices nowadays that easily result in elevation of the levels of nitrogenous wastes, especially ammonia and nitrite. Since diseases outbreak would cause serious economic loss in aquaculture industry, the immunity of aquaculture species is the main research sector. This study aimed to investigate the potential threat of isolated and combined exposure to ammonia and nitrite to innate immunity of white shrimp through study on transcriptional and enzymatic responses of phenoloxidase (PO) system in hemocytes. The results revealed that not only the expression levels of proPO-activating system related genes, proPO1, proPO2, proPO activating enzyme 1 (PPAE1), PPAE2, prophenoloxidase-activating factor (PPAF) and serine proteinase (SP) in hemocytes but also PO activity in plasma and hemocytes were significantly decreased in white shrimp exposed to isolated and combined stress of ammonia and nitrite. These findings were suggested that rising waterborne ammonia and nitrite individually or simultaneously may cause disruption of the molecular and enzymatic responses of PO system. However, combined treatment was presumed to cause greater hemocyte injury which resulted in reduction of total hemocyte count since hemolymph ammonia and nitrite levels raised concurrently. Accordingly, elevated ambient nitrogenous wastes influenced the PO system which may make white shrimp more susceptible to pathogen infection. This study provided the useful information for further field monitoring studies and may be helpful in identifying the impact of these stressors before severely harmful effects occur.