Effects of Environmental Factors on the Immune Responses of Freshwater Prawn Macrobrachium rosenbergii and Other Decapod Crustaceans

Abstract

The interactions of three sectors: deteriorated environment, weakening host and pathogen aggression are required to cause a disease outbreak. This paper reviews the existing information about the effects of physiological factors and environmental factors on the immune response in decapod crustaceans, particularly of freshwater prawn Macrobarchium rosenbergii. Emphasis is placed on intrinsic f actors and natural environments like gender, size, molting cycle, feeding rate, circadian rhythm and season. Primary physicochemical changes such as temperature, pH, dissolved oxygen, salinity, and pollutants such as ammonia and copper sulfate are also addressed. Immunological tools commonly used to evaluate immune response are hemocyte counts including THC (total hemocyte count) and DHC (differential hemocyte count), phenoloxidase activity, respiratory burst (release of superoxide anion), phagocytic activity, clearance efficiency (or antibacterial activity), and antimicrobial peptides. As an example, M. rosenbergii reared at high temperature (33-34℃), high pH (9.0-9.5), low pH (4.6-5.0), low DO (1.75-2.75 mg/l), and exposed to ammonia-N (0.55 mg/l) and copper sulfate (0.2 mg/l) experienced a decrease in phenoloxidase activity, leading to susceptibility to Lactococcus garvieae pathogen by reducing its immune ability. The immune responses of other decapod crustaceans under environmental changes and exposure to pollutants are also discussed.環境、病原及宿主間交互作用造成疾病的發生，環境不但影響宿主之生理及免疫抗病能力，同時也影響病原之致病力。本篇論文主要回顧十足目甲殼類尤其是淡水長臂大蝦Macrobrachium rosenbergii在不同內、外環境下其免疫抗病能力之反應。探討的因子包括：落石出內因性因子－性別、大小、脫殼週期及攝食量，自然環境－日週期及季節，主要物理化学因子－水溫、溶氧、pH及鹽度，代謝產物如氨以及治療劑如硫酸銅等。做為免疫活性之指標因子包括：總血球數、各型態血球數、酚氧化酵素、超氧離子、吞噬作用，清除作用（或殺菌力）及抗菌蛋白等。淡水長臂大蝦飼育於高水溫(33-34℃)，高pH (9.0-9.5)，低pH(4.6-5.0)，低溶氧（1.75-2.75毫克／升）以及暴露於氨－氮（0.55毫克／升）與硫酸銅（0.2毫克／升）中明顯降低其免疫力，增加對病原菌Lactococcus garvieae之敏感性。有關環境因子對其他十足目甲殼類免疫反應之影響本文中也有討論。