White shrimp Litopenaeus vannamei immersed in seawater containing Ulva lactuca powder and its extract showed increased immunity and resistance against Vibrio alginolyticus

Abstract

White shrimp Litopenaeus vannamei receiving fucoidan at 2, 6, and 10 μg g−1 after 0–144 h or 0–120 h were examined for immune parameters (haemograms, phenoloxidase activity, respiratory burst, and superoxide dismutase activity), proliferation of haemocyte in the haematopoietic tissue (HPT), gene expression, and phagocytic activity and clearance efficiency to Vibrio alginolyticus. Immune parameters and mitotic index of HPT increased after 3–24 h, reached their maxima after 48–72 h, and returned to background values after 144 h. Transcripts of lipopolysaccharide and β-1,3-glucan binding protein (LGBP), peroxinectin (PX), prophenoloxidase (proPO) I, proPO II, astakine, and haemocyte homeostasis-associated protein (HHAP) were up-regulated to a maximum after 48–72 h and returned to background values after 144 h. Phagocytic activity and clearance efficiency to V. alginolyticus increased after 12 h, reached its maximum after 48 h, and continued to remain higher after 120 h. In another experiment, shrimp receiving fucoidan after 48 h and 144 h were respectively challenged with V. alinolyticus at 6 × 106 colony-forming units (cfu) shrimp−1 or challenged with WSSV at 1.2 × 105 copies shrimp−1 and then placed in seawater. The survivalrate of shrimp receiving fucoidan was significantly higher than in controls. In conclusion, shrimp receiving fucoidan showed a proliferation of HPT, increased immune parameters, and up-regulated transcripts of LGBP, PX, proPO I, proPO II, astakine, and HHAP after 48 h. Shrimp receiving fucoidan exhibited a defense against V. alginolyticus and WSSV, even after immune parameters recovered to background levels.白蝦（Litopenaeus vannamei）給與石蓴（Ulva lactuca）粉末、及其濾液、殘留物、萃取物，以體外和體內實驗，研究原酚氧化酵素活性、免疫力、溶藻弧菌抵抗。在體外實驗，白蝦血淋巴球經石蓴粉末、及其濾液、殘留物、萃取物培養，顯示酚氧化酵素（phenoloxidase）活性及超氧離子（superoxide anion）增加。白蝦浸泡500 mg/l石蓴粉末、及其濾液、殘留物，200 mg/l萃取物，經1，3，5小時，檢測透明球（hyaline cell），顆粒球（granular cell，包含半顆粒球），總血球（total hemocyte count），酚氧化酵素活性及超氧離子，發現經3－5小時後，免疫因子均顯著高於控制組。白蝦浸泡石蓴粉末、及其濾液、殘留物、萃取物，經3小時後，感染溶藻弧菌1 × 10^6 cfu（colony-forming unit），放置於海水，觀察存活率。發現經接受石蓴物質後的白蝦，經24－120小時，其存活率均大於控制組。白蝦接受石蓴粉末、及其濾液、殘留物、萃取物，其吞噬作用（phagocytic activity）和清除能力（clearance efficiency）顯著高於控制組。實驗証實白蝦血球接受石蓴粉末，及其濾液，殘留物，萃取物，活化原酚氧化酵素系統。白蝦浸泡於含石蓴粉末500 mg/l、及其濾液、殘留物、以及浸泡200 mg/l萃取物，提升免疫力，抵抗溶藻弧菌感染。