title: Effect of hypoxia on the immune response of giant freshwater prawn Macrobrachium rosenbergii and its susceptibility to pathogen Enterococcus.
abstract: Giant freshwater prawns Macrobrachium rosenbergii (14-19 g) were challenged with Enterococcus (3 x 10(5) cfu prawn(-1)) previously incubated in TSB medium for 24 h, then placed in water having concentrations of dissolved oxygen (DO) at 7.75, 4.75, 2.75 and 1.75 mg l(-1). Onset of mortality occurred after 6 h exposure to 1.75 mg l(-1) DO, and after 12 h exposure to 2.75 mg 1(-1) DO. Cumulative mortality of prawns at 1.75 mg l(-1) DO was significantly higher than that at 4.75 and 2.75 mg l(-1) DO, and cumulative mortality of prawns at 4.75 and 2.75 mg l(-1) DO was significantly higher than that at 7.75 mg l(-1) DO after 96 h. The prawns (20-30 g) which had been placed in water for 0 to 120 h at 7.75, 4.75, 2.75 and 1.75 mg l(-1) DO were examined for the THC (total haemocyte counts), DHC (differential haemocyte counts), phenoloxidase activity, respiratory burst, percentage phagocytosis and clearance efficiency. No significant difference in semi-granular cells and granular cells of prawns was observed among four treatments. The prawns following 120 h exposure to 2.75 mg l(-1) DO decreased significantly the hyaline cells and THC by 39% and 36%, respectively. Phenoloxidase activity and respiratory burst decreased significantly by 33% and 11% when the prawns were exposed to 2.75 mg l(-1) DO after 24 h, respectively. Percentage phagocytosis and clearance efficiency to Enterococcus decreased significantly by 44% and 54% for the prawns following 12 h exposure to 2.75 mg l(-1) DO, respectively. It is concluded that DO as low as 2.75 mg l(-1) and 4.75 mg l(-1) causes depression in immune system of M. rosenbergii, and increases its susceptibility to Enterococcus infection.
authors.affiliation: Department of Aquaculture, National Pingtung University of Science and Technology, Pingtung, Taiwan, 912, Republic of China.
authors.forename: Winton
authors.initials: W
authors.lastname: Cheng
authors.forename: Chun-Hung
authors.initials: CH
authors.lastname: Liu
authors.forename: Jung-Ping
authors.initials: JP
authors.lastname: Hsu
authors.forename: Jiann-Chu
authors.initials: JC
authors.lastname: Chen
mesh_terms: D000818:Animals; D001772:Blood Cell Count / Q000662:veterinary; D015169:Colony Count, Microbial / Q000662:veterinary; D004198:Disease Susceptibility / Q000662:veterinary; D016983:Enterococcus / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity*; D006434:Hemocytes / Q000166:cytology; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D033541:Palaemonidae / Q000276:immunology* / Q000382:microbiology*; D010587:Phagocytosis / Q000187:drug effects; D016897:Respiratory Burst / Q000187:drug effects; D016019:Survival Analysis
chemical_list: D010100:Oxygen