Dietary protein requirement of giant mud crab Scylla serrata juveniles fed iso-energetic formulated diets having graded protein levels

The protein requirement of juvenile mud crab Scylla serrata (body weight=0.25±0.051 g, carapace width=9.3±0.04 mm) fed with different iso-energetic, iso-lipidic diets with graded protein levels (15–55% crude protein at 5% intervals) was determined. The feeding trial was conducted for a period of 63 days to determine the minimum and optimum protein requirement of juvenile S. serrata . The crabs fed with 15% and 20% dietary protein levels showed 100% and 12.5% of mortalities respectively. The mortalities observed in the above treatments were associated with the prolonged intermoult duration (46 and 32 days respectively). All other treatments recorded 100% survival. The best growth performance as well as the nutrient turn-over was recorded in crabs fed with 45% crude protein in the diet. Second-order polynomial regression of specific growth rate (SGR) as well as body protein gain vs. dietary protein levels suggested that 46.9–47.03% dietary protein is required for the best growth response and protein deposition in juvenile S. serrata . An extrapolation of 'SGR' and 'daily protein gain' upon the 'dietary protein level' axis ( Y =0) showed that 14.7–16.2% dietary protein is necessary for the minimum maintenance metabolism.     

温度变化对锯缘青蟹免疫因子的胁迫影响

试验结果表明,温度变化对养殖锯缘青蟹免疫能力的影响显著。20℃时血细胞密度最高,远离20℃后,其血细胞密度随温度的上升或下降而逐渐降低,在10℃和30℃时降至最低;血细胞吞噬百分比在不同试验温度下无显著差异,但血细胞吞噬指数在25~27℃时极显著高于其他温度。血清溶菌酶和碱性磷酸酶活性皆在25℃时最高,并随温度的升高或降低而下降;酸性磷酸酶活力在20℃时最高,并随温度的升高或降低而下降;超氧化物歧化酶在不同试验温度下无显著差异;过氧化物酶在30℃时活性最低,其他各试验组间没有显著差异;酚氧化酶活性在30℃和27℃最高,其他各试验组间没有显著差异。试验结果表明,水温为20~25℃,锯缘青蟹相关免疫因子的各项指标较好,反映此时锯缘青蟹的抗病能力较强,而偏离该温度区间明显影响锯缘青蟹的免疫水平。     

两种青蟹幼蟹水泥池套放网箱中间培育的比较研究

在水温25～27℃、盐度13～16、pH值7.5～8.5、连续充气的条件下,以PVC管和筛绢网制成的网箱进行拟穴青蟹(Ⅰ组)和锯缘青蟹(Ⅱ组)两种蟹苗的中间培育。结果表明:网箱培育的拟穴青蟹与锯缘青蟹的蜕壳率分别为47.28%和42.72%,彼此差异显著(p0.05);死亡率分别为32.88%和42.19%,彼此差异显著(p0.05)。Ⅰ组、Ⅱ组的增肉系数分别为21.10,14.17;甲长增长率分别为337.25%,304.99%;甲宽增长率分别为275.00%,204.42%。Ⅰ组、Ⅱ组的甲长与甲宽的关系分别为yⅠ=1.6455xⅠ-1.8486,yⅡ=1.7406xⅡ-2.7513;甲宽与体质量的关系分别为wⅠ=0.0264eⅠ0.2818x,wⅡ=0.0308e0Ⅱ.2772x;在本实验条件下青蟹密度为417只/m2时的存活率最高。表明水泥池套养网箱的中间培育模式是可行的。     

Efficacy of various lipid supplements in formulated pellet diets for juvenile Scylla serrata

Efficacy of sunflower oil (diet SF) and soybean oil (diet SB) alone and in combination with cod liver oil (diets M1‐2.80:1.40:1.40, M2‐2.80:2.24:0.56 and M3‐2.80:0.56:2.24; cod liver oil:sunflower oil:soybean oil) as lipid supplements (5.6%) in formulated diets (crude fat ～9.79%) for juvenile Scylla serrata (weight=0.28±0.07 g, carapace width=9.7±0.1 mm) were compared with diet CL, containing cod liver oil alone as the lipid supplement (6 diets × 24 crabs stocked individually, randomized block design). Growth performance, nutrient (protein and lipid) intake and gain of crabs fed M1, M2 and M3 were higher (P≤0.05) than the crabs fed SF and SB, but were not significantly different (P≥0.05) from crabs fed CL. Dietary fatty acids (FAs) are found to influence the FA profile of test crabs. Higher tissue levels of 16:1n‐7, 18:1n‐9 and 18:1n‐7 reflected the essential FA deficiency in crabs fed diets supplemented only with vegetable oils. Results confirmed that S. serrata could utilize vegetable oil supplements in the formulated diets as a partial replacement (50%) of cod liver oil without compromising growth and survival. Partial substitution of marine fish oil with suitable vegetable oils can reduce the feed cost considerably, in the context of rising fish oil prices.     

孵化水体pH值对锯缘青蟹胚胎发育的影响

采用组织学、光学显微镜和卵离体培育法,探讨孵化用水pH对锯缘青蟹(Scyllaserrata)胚胎发育影响。研究结果表明:锯缘青蟹胚胎发育孵化水体适宜pH值7.0~9.0,最适pH值为7.8~8.2;pH值对锯缘青蟹孵化率、畸形率和成活率的影响相对显著,但对孵化时间影响不显著;pH值范围在7.0~7.8和8.2~9.0对锯缘青蟹孵胚胎发育影响大于7.8~8.2。     

盐度突降对拟穴青蟹大眼幼体生长发育和Na~+/-K~+-ATPase活性的影响

研究了盐度突降对拟穴青蟹(Scylla paramamosain)大眼幼体生长发育和Na+/-K+-ATPase活性的影响。实验用水由海水和淡水配制成20%、40%、60%、80%和100%SW,其盐度分别为6.4、12.8、19.2、25.6和32.0。在不同环境盐度突降条件下,盐度6.4处理组拟穴青蟹大眼幼体在24 h内全部死亡;盐度12.8、19.2、25.6和32.0处理组拟穴青蟹大眼幼体的存活率无显著差异(P≥0.05),各处理组幼体蜕皮持续时间分别为2、2、3和4 d;当发育至C1期第2天时,盐度12.8处理组体重平均增量低于盐度19.2、25.6和32.0处理组,且差异显著(P<0.05)。盐度6.4处理组酶活性从实验开始即急速增加,至6 h时与其它各组呈显著差异(P<0.05);盐度32.0处理组酶活性从实验开始就下降,至72 h后变化趋于平缓;盐度12.8、19.2和25.6处理组酶活性在6 h内逐渐上升,之后迅速下降,于72 h时降至最低,之后酶活性变化趋于平缓。在96~120 h内,盐度12.8处理组酶活性始终显著高于25.6和32.0处理组(P<0.05)。结果表明,拟穴青蟹大眼幼体生长的最适盐度为19.2,适宜生长盐度下限在12.8~19.2之间,生存盐度下限在6.4~12.8之间。     

采用LC/MS~n法分析恩诺沙星在锯缘青蟹血浆中的代谢产物

采用电喷雾离子阱质谱法在正离子检测方式下,对锯缘青蟹口灌恩诺沙星给药后血淋巴中恩诺沙星和代谢产物进行定性分析。通过对血浆中恩诺沙星及其代谢产物的质谱裂解行为进行碰撞诱导解离分析,获得了各化合物的多级质谱信息,通过比较各化合物结构和质谱裂解途径的异同点,发现有三个代谢产物,其中峰面积最大的为环丙沙星,其次为羟基化恩诺沙星,另一代谢产物可能是加氧恩诺沙星;推测恩诺沙星在锯缘青蟹体内的代谢反应主要是脱乙基反应、羟基化反应和氧化反应。通过定量分析,血浆中恩诺沙星和代谢产物环丙沙星的浓度分别为19.1μg/ml和0.526μg/ml。     

锯缘青蟹呼肠孤病毒p40蛋白的体外表达与单克隆抗体制备

锯缘青蟹呼肠孤病毒(Scylla serrata reovirus,SsRV)第9节段(S9)编码的p40蛋白可能为病毒的甲基转移酶(methyltransferase)。为了便于确认p40在病毒复制过程中扮演的角色,将S9片段的开放阅读框(ORF)克隆到原核表达载体pET28a(+),实现了在宿主表达菌E.coli BL21(DE3)中的高效表达,进而纯化了重组表达蛋白p40(rp40),并制备了抗SsRV p40蛋白的2株单克隆抗体(4B7、3E5)。经Western blot分析表明,2株单克隆抗体均可特异地识别rp40蛋白,以及识别SsRV病毒蛋白中分子量为46 ku和40 ku 2条蛋白条带。实验结果不但确认SsRV p40为SsRV的结构蛋白,也提示p40和p46蛋白可能具有相同的抗原表位。为该蛋白的后续功能研究奠定了基础。     

The effects of supplemental dietary cholesterol on growth, development and survival of mud crab, Scylla serrata, megalopa fed semi-purified diets

The effects of varying levels of dietary cholesterol on growth, development time and survival of mud crab, Scylla serrata megalopa were investigated using semi-purified microbound diets (MBD). Five iso-energetic diets containing different level of cholesterol ranging from 0.14% to 1% of dry weight of the diet were tested. Fifteen megalopa were reared individually for each dietary treatment, and development time and survival were recorded on a daily basis. More than 25% of megalopa from all treatments were able to metamorphose into the first crab stage, suggesting that the endogenous level of cholesterol in the basal diet (0.14%) was sufficient to support development of the megalopa stage of this species. Widest mean carapace width (3.53 ± 0.08 mm) and highest mean dry weight (2.11 ± 0.22 mg) were recorded for juveniles that molted from megalopa fed live Artemia, whereas no megalopa in the unfed control treatment metamorphosed into crabs. The average development time from megalopa to the juvenile crab stage varied between the treatments, where megalopa fed live Artemia or MBD containing 0.2%, 0.4% or 0.8% total cholesterol showed the most synchronized molting (between 8.0 and 9.9 days). Longest development time was recorded for the megalopa fed diets containing 0.14% or 1% total cholesterol (both 11 days). Highest survival (74.3%) was recorded for the megalopa fed a diet containing 0.8% cholesterol. The results of this study are valuable in research to develop formulated diets for mud crab larvae as a replacement for live food in hatchery culture.