Preference of the Herbivorous Marine Teleost Siganus canaliculatus for Different Macroalgae

The decomposition of a large amount of unexploited macroalgal resource along the coast of China often results in heavy environmental pollution. In order to pave a way of using macroalgae as the dietary ingredient of rabbitfish Siganus canaliculatus, one of a few farmed herbivorous marine teleosts in China, its preference(feeding selectivity) for different macroalgae was determined in this study. Seven seaweed species abundantly inhabiting the coast of east Guangdong Province were exposed simultaneously to rabbitfish juveniles in laboratory(multiple-choice feeding) with their content and absolute intake assayed. It was found that the most preferred algae were Ulva prolifera, Gracilaria lemaneiformis and Chaetomorpha linum, less preferred algae were U. pertusa and Porphyra haitanensis, and least preferred ones were Sargassum fusiforme and Corallina sessilis. Such an order did not change when one to four relatively preferred seaweeds were removed. The preferred seaweeds were richer in protein and soluble sugar thus higher in energy than the least preferred. In addition, this fish was found to favor filamentous and flat algae rather than calcified ones. Accordingly, the richness of nutrients and morphological characteristics determined the preference of S. canaliculatus for tested macroalgae.

Effects of dietary supplementation of Ulva pertusa and non-starch polysaccharide enzymes on gut microbiota of Siganus canaliculatus

Fishes represent the highest diversity of vertebrates; however, our understanding of the compositions and functions of their gut microbiota is limited. In this study, we provided the first insight into the gut microbiota of the herbivorous fish Siganus canaliculatus by using three molecular ecology techniques based on the 16 S r RNA genes(denaturing gradient gel electrophoresis, clone library construction, and highthroughput Illumina sequencing), and the Illumina sequencing technique is suggested here due to its higher overall coverage of the total 16 S r RNA genes. A core gut microbiota of 29 bacterial groups, covering >99.9% of the total bacterial community, was found to be dominated by Proteobacteria and Firmicutes in fish fed three dif ferent diets with/without the supplementation of U lva pertusa and non-starch polysaccharide(NSP) enzymes(cellulase, xylanase, and β-glucanase). Diverse potential NSP-degrading bacteria and probiotics(e.g., R uminococcus, Clostridium and Lachnospiraceae) were detected in the intestine of the fish fed U. pertusa, suggesting that these microorganisms likely participated in the degradation of NSPs derived from U. pertusa. This study supports our previous conclusion that U. pertusa-based diets are suitable for the production of S. canaliculatus with lower costs without compromising quality.

Changes of visceral properties and digestive enzymes in the herbivorous marine teleost Siganus canaliculatus fed on different diets

The rabbitfish Siganus canaliculatus is one of the few cultured herbivorous marine teleosts. To better understand the digestive physiology of this fish and provide data for designing formulated feed using macroalgae as an ingredient, the changes of visceral properties and digestive enzyme activities were investigated after the juveniles were fed on different types of food including raw fish（RF）, formulated diet（FD） or macroalgae Enteromorpha prolifra（EP） and Gracilaria lemaneiformis（GL） for eight weeks. The results showed that the hepatosomatic and viscerosomatic indices in the RF and FD groups, as well as the relative intestine length（RIL） in the EP and GL groups, were significantly higher than those in other groups. Additionally, differences in the histological structure of the liver and anterior intestine were also observed among different dietary groups. The hepatic nuclei were displaced to the periphery by lipid inclusions in fish fed RF. The highest levels of mucosal folds were found in the anterior intestines of fish fed macroalgae. Digestive enzyme activity profiles showed obvious fluctuations in the first three weeks, and then leveled off in the following weeks. The levels of protease, lipase and α-amylase in the alimentary tract showed changes related to the levels of dietary protein, lipid and carbohydrate, respectively.Although macroalgae significantly inhibited the activity of protease in the stomach, it increased RIL and the number of mucosal folds in the anterior intestine so as to compensate for the influences on protease activities in the stomach. This study suggests that the digestive tract of rabbitfish can well adapt to different diets, and needs about three weeks to physiologically acclimatize to the nutritional status, thus implying that rabbitfish are somewhat omnivorous.

卵形鲳鲹营养需求与饲料研究进展

卵形鲳鲹(Trachinotus ovatus)是我国近年来快速发展起来的重要海水养殖鱼类,其年产量高达12万t。目前,国内外有关该鱼的营养需求与饲料研究已有较多报道,但对有些营养素的研究还是空白。本文主要就其蛋白质、氨基酸、脂肪、脂肪酸、碳水化合物和微量营养素的需求,蛋白源和脂肪源替代鱼粉和鱼油,功能性饲料添加剂应用等方面的研究进展进行综述,以期为该鱼的精准营养研究及高效低成本环保配合饲料的研发提供参考资料,从而推动其养殖业的健康可持续发展。

3种牛乳外泌体提取方法的比较

为筛选较好的牛乳外泌体提取方法,分别采用凝乳酶辅助法、等电点辅助法及EDTA辅助法提取牛乳中的外泌体,并通过纳米追踪分析、透射电子显微镜(TEM)观察、Western blot等方法来比较所提外泌体的形态、大小及蛋白浓度。结果显示:凝乳酶辅助法所获得的外泌体粒径符合正常的外泌体粒子直径范围,且粒子浓度极显著高于另外2种方法所提取的外泌体(P<0.01);凝乳酶辅助法所提取的外泌体数量较多,且外泌体双层膜结构完整且明显,背景清晰,而其他2种方法提取的外泌体杂质较多;凝乳酶辅助法所提外泌体中含有的溶酶体相关膜蛋白(CD63)和肿瘤易感基因(TSG101)2种标志性蛋白表达量显著高于其他2组(P<0.01)。提示:利用凝乳酶预处理牛乳后再对其进行超速离心,可以获得纯度更高的外泌体,试验结果为深入研究外泌体提供了实践基础。

Biodegradation ofEnteromorpha Polysaccharides by Intestinal Micro-Community from Siganus oramin

Micro-communities are supposed to have more potential functions of biodegradation of polysaccharides than single strain; however, the intestinal micro-communities involved in the biodegradation of Enteromorpha polysaccharides(EP) were seldom reported. In order to obtain the EP-degrading micro-community, the intestines of Siganus oramin was obtained to isolate the micro-communities, which were enriched by 0.3% of EP as the sole carbon source. A stable micro-community with EP degradative capability was achieved after seven generations of subculture, named H1. Results showed that H1 was able to degrade 75% of EP within 24 hours, and the activity of EP lyases reached 500 U m L^(-1) in 32 hours. With denaturing gradient gel electrophoresis(DGGE) and 16 S r RNA gene clone library analysis, ten bacteria closely related to Marinomonas pontica, Microbacterium sp., Leucobacter chironomi, Cyclobacterium sp., Algoriphagus winogradskyi, Pseudoalteromonas sp. and Vibrio sp. were determined. Furthermore, compared with the DGGE bands sequence and the clone library analysis, the dominant bacteria of the EP-biodegrading micro-community were Pseudoalteromonas sp. and Vibrio sp., with the respective proportion of 38% and 46%, and they should play an important role in EP degradation together with other degrading bacteria in the micro-community H1.

Effects of phenanthrene on hepatic enzymatic activities in tilapia(Oreochromis niloticus ♀×O.aureus ♂)

The effects of phenanthrene（Phe） on hepatosomatic index（HSI） and hepatic enzymatic activities in hybrid tilapia（Oreochromis niloticus ♀× O.aureus ♂） were investigated via the static freshwater exposure at dosage of 50,100,and 400 μg/L for 4-14 d.Compared with the control group,HSI was significantly decreased（P 〈 0.05） at 400 μg/L at day 14.Increased enzymatic activities（P 〈 0.05） were observed for catalase（CAT）,glutathione peroxidase（GPx） and superoxide dismutase（SOD） at either 100 or 400 μg/L at day 8 and 14,as well as for CAT at 50 μg/L at day 14,except for GPx at 400 μg/L at day 8.Ethoxyresorufin O-deethylase（EROD） activity was significantly increased（P 〈 0.05） at all dosage at day 4 as well as at 50 μg/L at day 8,but significantly decreased at either 100 or 400 μg/L at day 14（P 〈 0.05）.Glutathione-S-transferase（GST） activity was not affected.The results suggest that CAT,GPx,SOD and EROD,as well as HSI in tilapia may be used as the biomarkers or indexes for evaluating or monitoring the pollution of polycyclic aromatic hydrocarbons（PAHs） such as Phe.

黄斑蓝子鱼Δ6Δ5 Fads2蛋白重组表达和多克隆抗体的制备

黄斑蓝子鱼(Siganus canaliculatus)是首个被发现具有长链多不饱和脂肪酸(LC-PUFA)合成能力的海水鱼类,而脂肪酸去饱和酶(Fads2)是内源性合成LC-PUFA的关键限速酶.为深入研究鱼类Δ6Δ5 Fads2的生物学功能及其表达调控机制,本研究选取黄斑蓝子鱼Δ6Δ5 fads2基因的编码区序列长255 bp,通过限制性内切酶EcoR I和BamH I双酶切,将其插入质粒pGEX-6p-1,获得Δ6Δ5 fads2基因的重组表达载体,经IPTG诱导表达获得大量重组表达蛋白.以纯化后的Δ6Δ5 Fads2重组蛋白为抗原注射免疫KM小鼠后提取血清,并进行Western blot鉴定产生多克隆抗体的特异性.结果表明,本研究成功构建了pGEX-6p-1-Δ6Δ5 Fads2原核表达载体,表达纯化后获得大小约35.4 ku的Δ6Δ5 Fads2重组表达蛋白,利用KM小鼠得到的多克隆抗体特异性好,其效价约为1∶3.2×104.该抗体可为深入研究鱼类Δ6Δ5 Fads2的生物学功能及其表达调控机制提供基础条件,从而有助于研发提高鱼体内源性LC-PUFA合成能力的方法,降低养殖鱼类饲料中鱼油添加比例,促进养殖业的健康发展.

水产动物营养与饲料学实验教学改革初探

水产动物营养与饲料学是一门理论性和实践性都较强的学科。其实验教学又是理论联系实际的重要教学环节,也是培养学生实践创新能力必不可少的手段。因此,本文结合水产动物营养与饲料学课程培养目标与要求,对其实验教学内容、方法等进行了初步改革探索,旨在优化教学内容、教学方法,激发学生的学习兴趣,培养学生综合分析问题和解决问题的能力。