摄食水平对瓦氏黄颡鱼餐后代谢特征的影响

以新鲜泥鳅(Misgurus anguillicanndotus)肉块为饵料,采用麻醉灌喂的方法,在(25.0±0.5)℃条件下,研究了瓦氏黄颡鱼(Pelteobagrus vachelli)幼鱼[体重(7.03±0.15)g,n=42]不同摄食水平(饵料分别为体重的0%、1%、2%、4%和8%)对餐后代谢反应的影响.结果显示,在不同摄食水平下,瓦氏黄颗鱼摄食代谢均呈现先上升后下降的整体变化趋势;摄食水平由1%增加到8%,实验鱼的SDA耗能、SDA时间和摄食代谢峰值(PMR)分别从3.09 kJ/kg、8 h和56.08 mg O_2/kg·h增加到47.21 kJ/kg、36 h和97.25 mgO_2/kg·h;其中,8%(饱足摄食水平)和4%摄食水平组的代谢率在峰值水平能够持续20 h左右.瓦氏黄颡鱼最大运动代谢率(MMR)为166.5 mg O_2/kg·h,显著大于饱食组PMR(P＜0.05).本研究还表明,随摄食水平上升,瓦氏黄颡鱼通过PMR的增加和SDA时间的延长来满足SDA耗能增加的需求;从摄食4%组和8%组相似的梯形摄食代谢曲线,可以看出瓦氏黄颡鱼在高摄食水平条件(＞4%)下限制了摄食代谢的上升;PMR相对于静止代谢上升倍率较小,暗示其摄食占据的代谢空间较小,进而保留了大量剩余代谢空间用于运动和其他生理活动,这可能与其活跃的觅食活动习性有关.     

瓦氏黄颡鱼的繁殖生物学研究

研究了长江中游嘉鱼至新滩口江段瓦氏黄颡鱼的繁殖生物学。性腺发育可分为6个时期。4-7月性成熟系数较高,为繁殖季节。雌、雄鱼的肥满度和脂肪系数在繁殖前和繁殖后各出现1个峰值,繁殖期出现最小值。绝对繁殖力为1088-19765(粒),平均7728±4093(粒);相对繁殖力为23-88(粒),平均55±16(粒)。绝对繁殖力与体长、体重和年龄呈显著的正相关,其中体重与绝对繁殖力的关系最密切。群体性比接近1:1。属一次性产卵类型。两性最小性成熟年龄均为2龄。为补充群体占优势的繁殖群体。     

瓦氏黄颡鱼与黄颡鱼的耗氧率及窒息点

在平均水温25℃条件下,测得平均体重10.0 g的瓦氏黄颡鱼(Pelteobagrus vachelli)及平均体重12.6g的黄颡鱼(P.fulvidraco)耗氧率分别为0.21和0.23 mg/g.h,窒息点分别为0.91和0.75 mg/L;平均体重75.8 g的瓦氏黄颡鱼及平均体重85.4 g的黄颡鱼耗氧率分别为0.16和0.12 mg/g.h,窒息点分别为0.77和0.54 mg/L。分析表明,瓦氏黄颡鱼的耗氧率和窒息点都高于黄颡鱼。     

瓦氏黄颡鱼年龄与生长的研究

根据在长江中游嘉鱼至新滩口江段采集的瓦氏黄颡鱼标本,对其年龄与生长进行了研究。以脊椎骨为年龄鉴定材料,胸鳍棘和耳石作为对照材料。透射光下,脊椎骨上较宽的暗带和较窄的亮带相间排列成同心圆环,一个暗带和一个亮带构成一个年轮。2—7月形成新年轮,脊椎骨上不存在幼轮。雌、雄鱼的脊椎骨半径与体长呈显著的正相关,回归方程分别为:L_♀=6.95 131.46R-10.12R~2,L_♂=18.06 113.64R-1.70R~2。体长与体重的关系方程分别为:W_♀=1.85×10~(-5)L~(2.98),W_♂=1.69×10~(-5)L~(2.55)。雌鱼为等速生长,雄鱼为异速生长。雌、雄鱼的生长存在差异,1龄后雄鱼生长明显快于雌鱼。雌、雄鱼适宜的生长方程分别为:♀:L_t=300.88e~(-1.67e~(-0.42t)),W_t=511.77e~(-4.98e~(-0.38t)),♂:L_t=415.15e~(-1.96e~(-0.33t)),W_t=777.53e~(-4.92e~(-0.32t))。雌鱼体长、体重生长的拐点年龄分别为1.22龄和4.22龄,雄鱼分别为2.04龄和4.98龄。     

应用DNA分子标记鉴定黄颡鱼、瓦氏黄颡鱼及其杂交种的研究

为区分黄颡鱼（Pelteobagrus fulvidraco Richardson）、瓦氏黄颡鱼（Pelteobagrus vachelli Richardson）及其杂交种,前期研究构建了一个YY超雄黄颡鱼的BAC文库并筛选到了一个包含性别连锁标记Pf62-Y的BAC克隆。研究对该BAC克隆进行测序并鉴定到了一个新基因Inad-like,而且Inad-like的外显子序列在X和Y染色体上基本一致。通过黄颡鱼Inad-like的外显子序列及序列的保守性我们设计引物在瓦氏黄颡鱼中扩增获得了其部分内含子序列。通过内含子序列比对,发现瓦氏黄颡鱼比黄颡鱼少了一个DNA片段。基于黄颡鱼和瓦氏黄颡鱼的显著遗传差异,设计了一对引物,该引物在黄颡鱼和瓦氏黄颡鱼基因组中分别扩增出1908和1178 bp DNA片段,而且在杂交黄颡鱼中同时扩增出这两个DNA片段。总之,这个新的遗传标记提供了一种稳定、高效识别黄颡鱼及其与瓦氏黄颡鱼杂交种的方法。     

饥饿胁迫对瓦氏黄颡鱼脂肪代谢的影响

在水温(252)℃条件下, 对初始体重为(23.652.82) g的瓦氏黄颡鱼进行30d饥饿处理, 于饥饿第0、第7、第15和第30天取样, 分析了饥饿胁迫对瓦氏黄颡鱼的生长、体成分、脂肪酸组成和脂肪代谢相关基因表达的影响. 结果表明: 饥饿胁迫显著降低了瓦氏黄颡鱼肥满度、脂体比及肝体指数(p0.05). 肌肉脂肪含量也随着饥饿时间的延长而下降(p0.05). 肝脏中的饱和脂肪酸和肌肉中的单不饱和脂肪酸显著下降, 而肝脏中多不饱和脂肪酸和单不饱和脂肪酸及肌肉中的多不饱和脂肪酸显著上升(p0.05). 此外, 肌肉中的n-6和n-3及肝脏中的n-6多不饱和脂肪酸显著上升, 而肝脏中的n-3多不饱和脂肪酸显著下降(p0.05), 表明瓦氏黄颡鱼饥饿期间主要消耗饱和脂肪酸及单不饱和脂肪酸供能, 保留多不饱和脂肪酸. 饥饿胁迫15-30d, 瓦氏黄颡鱼肝脏脂蛋白酯酶、肝酯酶及肉碱酰基转运酶mRNA表达显著高于对照组(0d)(p0.05), 而脂肪酸结合蛋白及脂肪酸合成酶mRNA的表达显著低于对照组(p0.05), 表明饥饿胁迫可能会促进肝脏脂肪分解供能, 降低脂肪的生物合成.       

瓦氏黄颡鱼的胚后发育观察

2002年5~6月,在四川省泸州市、合江县分数批收集到长江野生瓦氏黄颡鱼(Pelteobagrusvachelli)亲本,通过人工催产、人工授精获得受精卵,对其胚后发育过程进行了观察。瓦氏黄颡鱼的胚后发育过程可以分为卵黄囊仔鱼、晚期仔鱼和幼鱼3个阶段。初孵仔鱼淡黄色,肌节40对,平均全长5.2mm。水温20~22℃时,孵出后第3d口张开;第7d开始摄食;第9d卵黄吸尽,此时鱼苗平均全长12mm,卵黄囊仔鱼阶段结束。晚期仔鱼阶段的仔鱼,胸鳍、尾鳍、臀鳍、背鳍、腹鳍先后发育,至鳍褶消失时晚期仔鱼阶段结束。经过30d的生长和发育,进入幼鱼阶段;此时平均全长达37mm,其形态特征和生态习性均与成鱼相似。     

温度对瓦氏黄颡鱼胚胎发育的影响

受精卵的孵化率、胚胎发育各阶段的存活率及发育速度是鱼类胚胎发育过程的重要生物学参数,各种内、外环境因素对这些参数均有不同程度的影响(Paninietal.,2001;ZachariaandKakati,2004)。水温、溶氧、pH值、光照及遗传变异等对鱼类胚胎发育均有影响(曹振东、谢小军,1994;吴贤汉     

鳔等睾吸虫对寄主瓦氏黄颡鱼的影响

对从嘉陵江北碚江段采集到的264尾瓦氏黄颡鱼的调查表明,瓦氏黄颡鱼感染鳔等睾吸虫的感染率和感染强度分别为25．70％和1．50;体长在12－18cm的个体感染的可能性增大,而体长在14－15cm之间的个体感染率最高,为38．00％;此外还比较了感染鱼和未感染鱼的肥满度（F）、脂肪系数（ASI）、肝系数（HSI）,发现鳔等睾吸虫对瓦氏黄颡鱼的肥满度有显著影响,感染鱼的肥满度下降了16．20％,对脂肪系数、肝系数的影响不显著。感染鱼的肝脏、肠系膜等器官均有不同程度的病变。     

瓦氏黄颡鱼和岩原鲤脾脏的组织学观察

运用组织学方法对瓦氏黄颡鱼和岩原鲤脾脏的显微结构进行了研究.瓦氏黄颡鱼和岩原鲤脾脏被膜薄,仅由一层单层扁平上皮细胞和结缔组织纤维构成,脾小梁明显,红髓和白髓混合,无明显的分界,鞘毛细血管发达;瓦氏黄颡鱼脾小梁细而少,白髓中淋巴细胞密集,在靠近被膜的脾实质边缘区域密集的淋巴细胞形成外形类似淋巴小结的结构,巨噬细胞聚集形成明显的巨噬细胞中心;岩原鲤脾小梁发达,伸入脾实质将脾脏分隔成一个个的小叶,白髓中密集的淋巴细胞较少,未见类似淋巴小结的结构,巨噬细胞分散存在,无明显的巨噬细胞中心.     

速度增量及持续时间对瓦氏黄颡鱼幼鱼临界游泳速度的影响

为了考查速度增量(△v)和持续时间(△t)2个参数变化对鱼类临界游泳速度(critical swimming speed,Ucrit)的影响,于25℃条件下,首先以15%临界游泳速度作为△v,设置不同的持续时间(△t:5,10,15,30,60min);再以20min作为△t,设置不同的速度增量(△v:5%,10%,15%,20%,30%Ucrit),测定瓦氏黄颡鱼(Pelteobag vachelli)幼鱼的临界游泳速度。结果表明:随△t的增加Ucrit整体呈下降趋势,△t由5min增加至60min,绝对游泳速度(absolute swimming speed,Ua)由(47.4±0.7)cm.s-1下降至(39.1±1.5)cm.s-1(P<0.05),除15和30min无显著差异外,其余各组间均存在显著差异(P<0.05);而△v由5%提高至10%Ucrit,Ua由(44.1±0.6)cm.s-1显著增加至(47.0±0.4)cm.s-1(P<0.05),15%和20%Ucrit的Ua分别为(45.2±0.2)cm.s-1和(46.3±0.8)cm.s-1,与10%Ucrit组之间均无显著差异,但△v增...     

Parameterising a public good: how experiments on predation can be used to predict cheat frequencies

Chemical defence is superficially easy to understand as a means for individuals to protect themselves from enemies. The evolution of chemical defence is however potentially complex because such defences may cause the generation of a public good, protecting members of the population as a whole as well as individuals that deploy toxins defensively. If a public good of protection exists, it may be exploited and degraded by “cheats” that do not invest in defence. This can in turn lead to complex frequency (and density) dependent effects in toxin evolution. To investigate this we used ecologically relevant predators (Great tits, Parus major) and examined how individual and public benefits vary depending on the frequency of non-defended “cheating” prey and their spatial distribution. We found that the public benefit, of reduced attack probability, increased with increasing frequency of defended individuals. In contrast the individual benefit of chemical defence, measured as increased chance of rejection during an attack before injury, did not vary with the frequency of defended forms. Hence the selective dynamics of these two levels of benefits responded differently to the frequency of defended forms. Surprisingly, given the strong associations of chemical defences and grouping in animals, large aggregations did not help individuals in the group regardless of their defence status. The explanation for the result, may be that in our experiment birds did not have information about other potential aggregations (i.e. set up was sequential) and thus their giving up density was lower compared to the situations where set ups were simultaneous. We use behavioural data of our predators to construct a simple model of toxin evolution which can make quantitative predictions about the frequencies to which defence cheats evolve. We use this model to discuss how toxin evolution can be investigated in the wild and in laboratory settings.     

REG can be used to detect cerebrovascular alteration caused by alcoholism

Despite recent evidence of the beneficial effects of moderate alcohol consumption in arteriosclerosis prevention, the neurotoxic effects of alcohol abuse are well known. Our hypothesis was that uncontrolled alcohol consumption may cause cerebrovascular damage detectable by rheoencepholography (REG), a noninvasive bio-impedance technique for estimating cerebral blood flow. Test subjects were 48 alcoholic patients in Hungary; the control group consisted of 12 drug-addicted and depressed patients in Hungary and 13 healthy male subjects in the United States. Additional subgroups were formed according to smoking habits and average daily alcohol dose. REG was measured by a computer-based system, "Cerberus"; REG anacrotic time above 180 ms was considered pathological. ANOVA showed that daily alcohol consumption and smoking were significantly higher in alcoholics than in drug-addicted and depressed patients. Twelve alcoholics showed a pathological REG anacrotic time. Longer REG anacrotic time was correlated with higher daily alcohol consumption. In the alcoholic group, the steeper regression line of REG slope reflected the pathological impact of alcohol abuse. The healthy control sample showed a nearly identical slope for both REG and age. The correlation of increased REG anacrotic time and daily alcohol consumption supports the hypothesis that REG detects accelerated cerebrovascular aging (arteriosclerosis) in alcoholic subjects.     

A comparative study of feeding methods: Effect on the growth,behaviour and biochemical performance of juvenile Beluga sturgeon (Huso huso Linnaeus, 1758)

This study compared the influence of feeding methods on growth parameters of young‐of‐year Beluga sturgeon Huso huso in a 6‐week trial. Fish with an average weight 150.3 ± 0.8 g (±SE) were stocked into nine circular concrete tanks (30 fish per tank) in an open circular system with water temperature of 18.9°C. All fish were fed by three different feeding methods: (a) hand‐fed (HF), (b) continuously available (automated feeder; AF), (c) half of daily feed provided by hand, and another half by automated feeder (combined feeding). For the hand‐feeding method, fish were fed at 09:00, 14:00, 19:00, and 24:00. The entire automatic feeding groups were fed with the same amount of feed. The mean final body weight was the highest in fish fed by AF compared to fish fed by HF. Body weight increase, condition factor, specific growth rate, and feed conversion ratio did not differ among the feeding groups. Fish fed by AF revealed higher swimming activity than the HF group. No significant changes were found in hematocrit, glucose and total protein concentrations among treatments. The results showed less dependence of growth and physiology of Beluga sturgeon on feeding method, but automated‐feeding was shown to be suitable for sturgeon rearing because of further low labour costs in rearing systems.     

Cryopreserved Morulae can be used to Efficiently Generate Germline-transmitting Chimeras by Blastocyst Injection

The production of chimeric mice is a complex process, requiring the careful coordination of tissue culture cell growth, production of a large number (30–75) of competent blastocysts and the availability of appropriately timed pseudo pregnant female mice. Failure at any of these steps can impinge upon the rapid production of chimeras. One potential improvement for the efficient generation of chimeric mice would be the utilization of cryopreserved embryos suitable for injection. C57Bl/6 morulae were frozen using a standard 2-step protocol with ethylene glycol as the cryopreservation agent. We determined that cryopreserved morulae could thaw, culture to blastocyst stage in KSOM media and survive injection at rates equivalent to control embryos. Cryopreserved morulae were also equivalent to controls at all later stages in the process of production of chimeric mice, including birth rate, percentage chimerism of resulting animals and ability to produce germline progeny. Hence, cryopreservation of morulae for blastocyst injection is a suitable option to enhance the efficiency of chimeric mouse generation.     

Diagnostic PCR can be used to illuminate meiofaunal diets and trophic relationships

Analysis of the meiofaunal food web is hampered because few prey have features that persist long enough in a predator's digestive tract to allow identification to species. Hence, at least for platyhelminth predators, direct observations of prey preference are almost nonexistent, and where they occur, prey identification is often limited to the phylum level. Studies using an in vitro approach are rare because they are extremely time‐consuming and are subject to the criticism that predators removed from their natural environment may exhibit altered behaviors. Although PCR‐based approaches have achieved wide application in food‐web analysis, their application to meiofaunal flatworms suffers from a number of limitations. Most importantly, the microscopic size of both the predator and prey does not allow for removal of prey material from the digestive tract of the predator, and thus the challenge is to amplify prey sequences in the presence of large quantities of predator sequence. Here, we report on the successful use of prey‐taxon‐specific primers in diagnostic PCR to identify, to species level, specific prey items of 13 species of meiofaunal flatworms. Extension of this method will allow, for the first time, the development of a species‐level understanding of trophic interactions among the meiofauna.     

Membrane protein shaving with thermolysin can be used to evaluate topology predictors

Topology analysis of membrane proteins can be obtained by enzymatic shaving in combination with MS identification of peptides. Ideally, such analysis could provide quite detailed information about the membrane spanning regions. Here, we examine the ability of some shaving enzymes to provide large‐scale analysis of membrane proteome topologies. To compare different shaving enzymes, we first analyzed the detected peptides from two over‐expressed proteins. Second, we analyzed the peptides from non‐over‐expressed Escherichia coli membrane proteins with known structure to evaluate the shaving methods. Finally, the identified peptides were used to test the accuracy of a number of topology predictors. At the end we suggest that the usage of thermolysin, an enzyme working at the natural pH of the cell for membrane shaving, is superior because: (i) we detect a similar number of peptides and proteins using thermolysin and trypsin; (ii) thermolysin shaving can be run at a natural pH and (iii) the incubation time is quite short. (iv) Fewer detected peptides from thermolysin shaving originate from the transmembrane regions. Using thermolysin shaving we can also provide a clear separation between the best and the less accurate topology predictors, indicating that using data from shaving can provide valuable information when developing new topology predictors.     

Biting off more than you can chew: Attempted predation on a human by a giant snake (Simalia amethistina)

On 10 March 2014, a radio-tracked Australian scrub python (Simalia amethistina) made a predatory attack on a 64 kg sleeping woman. The snake was unsuccessful, but data from our radio-tracking programme suggest that predation attempts on oversized prey are not uncommon – even if they threaten the survival of the predator. We explore hypotheses about why snakes attempt to consume such large meals.     

非洲爪蟾胚胎细胞核移入花背蟾蜍成熟卵后的细胞学研究

This paper reports the development of the nuclear transplanted eggs obtained by transplanting Xenopus laevis blastomere nuclei to Bufo raddei. The formation of the donor nuclei is similar to that of the male pronuclei in the normal development egg in the early stage while shows degradation in the late stage after transplanting. The chromosome complement formes in some eggs 30 minutes after transplantation, which is assumed to contribute to the development of the transplanted eggs [Acta Zoologica Sinica 51 （5） ： 924 - 931, 2005].     

Cholesterol removal by some lactic acid bacteria that can be used as probiotic

In the present study, the relationship between exopolysaccharide production and cholesterol removal rates of five strains of Lactobacillus delbrueckii subsp. bulgaricus isolated from home‐made yoghurt was studied. Test strains were selected according to their exopolysaccharide production capacity. Influence of different bile concentrations on cholesterol removal was investigated. It was confirmed that B3, ATCC 11842 and G11 strains which produce high amounts of exopolysaccharide (211, 200 and 159 mg/l, respectively) were able to remove more cholesterol from the medium compared to those that produce low amounts of exopolysaccharide (B2, A13). The highest cholesterol removal (31%) was observed by strain L. delbrueckii subsp. bulgaricus B3, producing a high amount of exopolysaccharide, in 3 mg/ml bile concentration. Cholesterol removal by resting and dead cells was investigated and it was found to be 4%–14% and 3%–10%, respectively. Cholesterol removal by immobilized and free cells of the B3 strain was studied and it was determined that immobilized cells are more effective. Influence of cholesterol on exopolysaccharide production has also been tested and it was found that cholesterol increased the production of EPS. The results indicated that: (i) there is a correlation between cholesterol removal and EPS production; and (ii) L. delbrueckii subsp. bulgaricus B3 is regarded as a suitable candidate probiotic and adjunct culture.