The immunostimulatory effects of hot-water extract of Gelidium amansii via immersion, injection and dietary administrations on white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus |
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Authors: | Fu Yu-Win Hou Wen-Ying Yeh Su-Tuen Li Chiu-Hsia Chen Jiann-Chu |
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Institution: | Department of Aquaculture, College of Life Sciences, National Taiwan Ocean University, Keelung 202, Taiwan, ROC. |
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Abstract: | The total haemocyte count (THC), phenoloxidase activity, and respiratory burst were examined when white shrimp Litopenaeus vannamei were immersed in seawater (34 per thousand) containing hot-water extract of red alga Gelidium amansii at 200, 400 and 600 mg l(-1), injected with hot-water extract at 4 and 6 microg g(-1) shrimp, and fed diets containing hot-water extract at 0, 0.5, 1.0 and 2.0 g kg(-1). These parameters increased significantly when shrimp were immersed in seawater containing hot-water extract at 400 and 600 mg l(-1) after 1h, when shrimp were injected with hot-water extract at 6 microg g(-1) shrimp after one day, and when shrimp were fed diets containing hot-water extract at 1.0 and 2.0 g kg(-1) after 14 days. Phagocytic activity and clearance efficiency were significantly higher for the shrimp that were fed diets containing hot-water extract at 1.0 and 2.0 g kg(-1) than those of shrimp that were fed diets containing hot-water extract at 0 and 0.5 g kg(-1) after 14 and 28 days. In a separate experiment, L. vannamei which had received hot-water extract via injection, or fed diets containing hot-water extract, were challenged after 3h or 28 days with V. alginolyticus at 2 x 10(6) cfu shrimp(-1) and 1 x 10(6) cfu shrimp(-1), respectively, and then placed in seawater. The survival of shrimp that were injected with hot-water extract at 6 microg g(-1) was significantly higher than that of control shrimp after 1 day, and the survival of shrimp fed diets containing hot-water extract at 0.5, 1.0 and 2.0 g kg(-1) increased significantly after 3 days as well as at the end of the experiment (6 days after the challenge), respectively. It was concluded that L. vannamei that were immersed in hot-water extract at 400 mg l(-1), injected with hot-water extract at 6 microg g(-1) shrimp, and fed hot-water extract of G. amansii at 2.0 g kg(-1) or less showed increased immune ability as well as resistance to V. alginolyticus infection. |
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Keywords: | Litopenaeus vannamei Vibrio alginolyticus Hot-water extract of Gelidium amansii Immersion Injection Diet Immune parameter Resistance |
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