盐度对新吉富罗非鱼受精卵孵化和仔稚鱼活力的影响

研究了盐度梯度对新吉富罗非鱼(Oreochromis niloticus)受精卵孵化和仔鱼活力的影响。水温(28±0.5)℃下,观察比较了8个梯度的盐度(3‰、6‰、9‰、12‰、15‰、18‰、21‰、24‰)及纯净淡水(盐度为0)条件下,新吉富罗非鱼受精卵的孵化时间、孵化周期、孵化率和畸形率。同时在不同盐度条件下对4批初孵仔鱼进行耐饥饿实验,测定其不投饵存活系数(SAI)值。结果表明,新吉富罗非鱼受精卵在盐度6‰～15‰时,孵化率较高(89.0%～92.7%);盐度低于3‰和高于18‰时,孵化率较低。仔鱼生存适宜盐度3‰～15‰,最适盐度6‰～9‰。新吉富罗非鱼仔鱼在盐度0～3‰及18‰～24‰时,仔鱼的SAI值较低,不适宜仔鱼培育;盐度为6‰～15‰时,仔鱼的活力较高。仔鱼的SAI值与受精卵的孵化率呈正相关关系。     

四指马鲅(Eleutheronema tetradactylum)受精卵和仔鱼对不同盐度的耐受性

本文观察了11个盐度梯度(5、7、9、11、13、15、20、25、28、30、35、40、45,28作为对照组)下四指马鲅(Eleutheronema tetradactylum)不同发育阶段的受精卵的沉浮性质和孵化情况以及初孵仔鱼在不投饵条件下的存活情况,并测定不投饵存活系数(survival activity index,SAI)。结果表明:第一次分裂前和原肠期两发育阶段的受精卵在盐度低于25的海水中均呈沉性,盐度为25时则悬浮在水层中部,盐度28及以上呈浮性;第一次分裂前的受精卵对盐度改变较敏感,而原肠期受精卵对盐度胁迫产生一定的耐受性;盐度的改变对初孵仔鱼的存活率和SAI值影响比较大。综合分析孵化率、仔鱼畸形率以及SAI值,推测四指马鲅受精卵孵化的适宜盐度范围为25~35,最适孵化盐度为35。     

不同盐度下条石鲷胚胎及卵黄囊仔鱼的形态变化

为了研究盐度对条石鲷(Oplegnathus fascltus)胚胎及卵黄囊仔鱼生长发育的影响,将条石鲷的受精卵置于不同盐度的水体中, 观察盐度胁迫下条石鲷胚胎的沉浮情况、卵径、油球径、孵化率、畸形率, 以及孵化后卵黄囊仔鱼的形态变化和营养物质的消耗状况。结果表明:条石鲷受精卵在盐度25(含25)以下的水体中为沉性, 在盐度30(含30)以上的海水中全部漂浮于水表层, 在对照组盐度26的水体中大部分胚胎浮在水上层;在水温22.5 ℃～24.0 ℃的条件下, 条石鲷受精卵经24～30 h可孵化成仔鱼, 盐度对孵化时间影响不显著(P＞0.05);盐度为20～50都能孵出仔鱼, 但孵化率和畸形率因盐度不同而有显著差异;综合分析表明,条石鲷受精卵孵化的适合盐度范围为25～35,理论上的最适孵化盐度范围为28.5～30.5;受精卵卵径与孵化盐度呈反比,盐度与卵黄囊被吸收程度呈正比,与全长和体高呈反比,油球径不因盐度不同而改变。     

盐度及pH对星斑裸颊鲷受精卵孵化和仔鱼耐饥饿能力的影响

比较观察了不同盐度(0、5‰0、10‰、15‰、20‰、25‰、30‰、35‰、40‰和45‰)及不同pH(5.5、6.0、6.5、7.0、7.5、8.0、8.5、9.0和9.5)条件下,星斑裸颊鲷(Lethrinus nebulosus)受精卵的孵化时间、孵出期、孵化率、畸形率及一定时间内(24h和48h)仔鱼成活率,并且在以上盐度和pH条件下对星斑裸颊鲷初孵仔鱼进行耐饥饿试验,测定其不投饵存活指数(survival activity index,SAI).结果表明,只有SAI值大于3的星斑裸颊鲷仔鱼才有可能被进一步培育成苗,低于3的将在数天内死亡;星斑裸颊鲷受精卵孵化的适宜盐度范围是10‰～45‰,最适宜盐度范围15‰～40‰,适宜pH是6.5～9.0,最适宜pH范围7.0～8.5;初孵仔鱼生存的适宜盐度范围是10‰～40‰,最适宜盐度范围20‰～25‰,适宜pH是5.5～9.5,最适宜pH范围7.0～8.5.     

盐度对条石鲷胚胎发育的影响

为了确定条石鲷胚胎孵化的适宜盐度,在试验水温为23.0℃～25.2℃条件下,设置了8个盐度组进行条石鲷胚胎孵化试验,研究了盐度对条石鲷胚胎发育的影响。结果表明:低盐度和高盐度对胚胎有持续性伤害,均可造成胚胎和卵黄球在卵裂期收缩而死亡,一部分胚胎在原肠期之后收缩死亡;低盐度可造成初孵仔鱼畸形率增加,主要引起仔鱼脊柱"L"形和"C"形弯曲,而高盐度可导致胚体胚孔关闭以后尾部的畸形发育;通过分析各盐度组的孵化率、仔鱼畸形率和盐度之间的关系,得出健康仔鱼比例(PHL)和盐度(S)的关系式为PHL=-0.0018S2-0.1135S-0.8853(R2=0.948),以PHL70%为适宜孵化盐度范围,以PHL90%为最适孵化盐度范围,由此确定在23.0℃～25.2℃条件下,条石鲷的适宜孵化盐度范围为21～42(PHL70%),最适为30～33(PHL90%)。     

环境因素对缢蛏受精卵孵化率影响的研究

本文主要探讨了几种环境因素(温度、盐度、pH值、密度、化肥施用量及藻类)对缢蛏受精卵孵化率的影响。研究结果表明:受精卵孵化最佳条件为:温度20—25℃;pH值为7.0—8.5;适盐范围随亲蛏来源不同而异,来自低盐区的,最适盐度8—12‰,而来自高盐区的,15—30‰,温度可影响其适盐范围,25℃左右,其范围最广;受精卵的密度以50粒/毫升以下为宜;保持低浓度的藻类对其孵化有利;施用2ppm以下的硫酸铵和尿素,可促进藻类繁殖,对受精卵孵化的影响不大。     

盐度对裸项栉鰕虎鱼繁殖和生长的影响

目的探索裸项栉鰕虎鱼繁殖和育苗的适宜盐度。方法比较不同盐度梯度条件下裸项栉鰕虎鱼的产卵率、孵化率和生长存活情况。结果裸项栉鰕虎鱼性腺成熟、产卵和孵化的适宜盐度为10‰-20‰,过低或过高盐度该鱼产卵量少,孵化率极低;适宜的盐度有利于裸项栉鰕虎鱼的生长。结论裸项栉鰕虎鱼适盐范围广,适宜的繁殖、生长盐度较低。     

中国林蛙生长发育盐效应的研究进展

本文对中国林蛙受精卵、蝌蚪和幼蛙等不同发育阶段生长发育的盐效应进行了综述。盐度对不同发育阶段的中国林蛙均有影响。中国林蛙受精卵孵化的最适盐浓度范围为0~5 g/L,孵化率超过80%;在2~3 g/L盐浓度下孵化的中国林蛙雌性个体超过90%,孵化后中国林蛙蝌蚪的存活率没有显著变化;中国林蛙蝌蚪和变态幼蛙的安全盐度上限分别为2 g/L和1.5 g/L。这些研究结果为中国林蛙野生资源的保护和人工养殖提供了一定的理论基础。     

基于响应面法分析温度和盐度对虎斑乌贼受精卵孵化的联合影响

根据中心复合试验设计(CCD)原理,在单因素试验的基础上,采用响应曲面分析法,观察了温度(24~32℃)与盐度(25~35)对虎斑乌贼受精卵孵化率及平均孵化时间的联合影响。结果表明:温度和盐度的一次、二次及互作效应对孵化率与平均孵化时间均有显著影响(P0.05),随着温度的升高,孵化率呈先上升后下降的趋势,平均孵化时间呈减少的趋势;随着盐度的上升,孵化率呈先上升后下降的趋势,平均孵化时间呈先下降后上升的变化;所考察的因子与孵化率、平均孵化时间之间二次多项模型的决定系数分别达到0.9791和0.9774;回归方程优化结果显示,温度为27.6℃和盐度31.1时,孵化率最大值为88.11%;温度26.2℃和盐度29.6时,平均孵化时间最小值为21.8 d,两模型的可信度均高达0.985。建议虎斑乌贼受精卵在温度26~28℃,盐度29~31条件下进行孵化,以提高生产效率。     

长江口纹缟虾虎鱼胚胎发育及早期仔鱼生长与盐度的关系

研究了长江口纹缟虾虎鱼(Tridentiger trigonocephalus)胚胎发育及早期仔鱼生长与盐度的相关性。纹缟虾虎鱼胚胎发育时,盐度4与6试验组效果较好,受精率分别达(76.28±2.73)%与(74.63±5.49)%,孵化率分别达(66.95±2.99)%与(62.15±2.18)%,出膜时间分别为(228.8±5.9)h与(221.5±5.2)h,器官发育特征较明显,畸形率较低。纹缟虾虎鱼仔鱼发育时,初孵仔鱼全长(2.534±0.078)mm,卵黄囊长径(0.421±0.047)mm,短径(0.369±0.038)mm,5日龄时卵黄囊基本消失,初步形成消化器官、循环器官和运动器官等。盐度8与10水体孵育的仔鱼畸形率达5―20%,其他试验组略低。盐度4与6试验组仔鱼的器官发育速度快于其他3个试验组。盐度0―6试验组纹缟虾虎鱼仔鱼生存活力指数（SAI）为41.83―46.83,仔鱼活力较好,而盐度8―10试验组SAI值为23.43―29.13,活力较差。综合各项指标表明,在盐度0―10范围内,长江口纹缟虾虎鱼胚胎发育的适宜盐度为4―6,早期仔鱼生长的适宜盐度为2―4。     

Time dependency of molecular rate estimates and systematic overestimation of recent divergence times

Studies of molecular evolutionary rates have yielded a wide range of rate estimates for various genes and taxa. Recent studies based on population-level and pedigree data have produced remarkably high estimates of mutation rate, which strongly contrast with substitution rates inferred in phylogenetic (species-level) studies. Using Bayesian analysis with a relaxed-clock model, we estimated rates for three groups of mitochondrial data: avian protein-coding genes, primate protein-coding genes, and primate d-loop sequences. In all three cases, we found a measurable transition between the high, short-term (< 1-2 Myr) mutation rate and the low, long-term substitution rate. The relationship between the age of the calibration and the rate of change can be described by a vertically translated exponential decay curve, which may be used for correcting molecular date estimates. The phylogenetic substitution rates in mitochondria are approximately 0.5% per million years for avian protein-coding sequences and 1.5% per million years for primate protein-coding and d-loop sequences. Further analyses showed that purifying selection offers the most convincing explanation for the observed relationship between the estimated rate and the depth of the calibration. We rule out the possibility that it is a spurious result arising from sequence errors, and find it unlikely that the apparent decline in rates over time is caused by mutational saturation. Using a rate curve estimated from the d-loop data, several dates for last common ancestors were calculated: modern humans and Neandertals (354 ka; 222-705 ka), Neandertals (108 ka; 70-156 ka), and modern humans (76 ka; 47-110 ka). If the rate curve for a particular taxonomic group can be accurately estimated, it can be a useful tool for correcting divergence date estimates by taking the rate decay into account. Our results show that it is invalid to extrapolate molecular rates of change across different evolutionary timescales, which has important consequences for studies of populations, domestication, conservation genetics, and human evolution.     

Predation rate and numerical response of Aphidoletes aphidimyza feeding on different densities of Aphis craccivora

Predation rate and numerical response are basic to any investigation of predator–prey relationships and key components in the selection of predators for biological control. The density-dependent predation rate and numerical response of Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) to varying densities (5, 10, 20, 40, 60 and 80) of third-instar Aphis craccivora (Koch) (Hemiptera: Aphididae), were studied in laboratory conditions [23±1°C, 70 ± 5% relative humidity (RH), and a photoperiod of 16:8 h L:D. Predation rate data were analysed using the age-stage, two-sex consumption rate software. Net consumption rate (C₀) increased by increasing prey density. The lowest and highest net consumption rates were 20.75 and 190.8 prey nymphs at densities of 5 and 80 A. craccivora. The transformation rate from prey population to predator offspring (Q_p) increased by increasing prey density. The reproductive numerical response, in terms of eggs laid, increased curvilinearly with increasing prey density. Females laid 121.375 ± 4.301 eggs when exposed to the highest prey density (80) and 52.5 ± 1.544 eggs at lowest prey density (5). It can be concluded that different densities of A. craccivora influenced the reproductive performance of A. aphidimyza in terms of predation rate and numerical response.     

On-station comparative analysis of reproductive and survival performance between Red Maasai,Dorper, and Merino sheep breeds

The reproductive performance of ewes and the survivability of lambs to weaning have a critical economic impact on sheep farming worldwide. Further, knowledge of major mortality causes allows an opportunity for improved flock management to evade financial losses. The maximum likelihood estimates for generalised linear mixed models and chi-square test methods were used to examine 971 mating records, 839 and 763 lambs born and weaned (singles or twins) from the Naivasha Sheep and Goats station in Kenya for the years 2011 to 2020 consisting of Dorper, Red Maasai (RedM), and Merino breeds. The RedM (P < 0.05) outperformed Dorper and Merino in weaning rate, whereas reproductive performance between the three breeds was not significantly different (P > 0.05) in litter size and multiple lambings per ewe lambing. On the one hand, Dorper significantly (P < 0.05) outperformed the other two breeds only in weaning weight per lamb born. In addition, among all the major causes of death, pneumonia appeared to be the one to which Dorper breeds were most susceptible (chi-square test, P < 0.05). According to the findings of this study, neither the Dorper nor the Merino sheep breeds were reproductively superior to the RedM in an extensive semi-arid production environment. In addition, Dorper's susceptibility to the leading causes of mortality, particularly pneumonia and sheep pox, were relatively high compared to other breeds and could be a precursor to massive economic losses for Dorper sheep producers. In contrast to the indigenous RedM breed, imported sheep breeds appeared to be more susceptible to major mortality-related under an extensive production system. Therefore, regardless of weaning weight, RedM breed production appears to be a more viable investment for small-scale farmers, particularly in semi-arid regions.     

光周期和温度对虎斑蝶卵、幼虫及蛹存活的影响

通过在人工气候箱内设定不同光周期和温度梯度单虫饲养观察个体发育史,研究了光周期和温度对虎斑蝶Danaus genutia幼期存活的影响,研究结果可为该高观赏价值蝶种的规模化养殖提供依据。结果表明,在长光照(L∶D=15∶9)条件下,17.5、20.0、22.5、25.0、27.5、30.0℃时虎斑蝶卵的孵化率分别为63.72%、71.67%、65.75%、75.00%、67.12%、59.56%,幼虫的存活率分别为85.67%、85.96%、91.19%、89.20%、80.86%、68.78%,蛹的存活率分别为82.76%、100.00%、96.00%、97.06%、100.00%、100.00%;在短光照(L∶D=9∶15)条件下,17.5、20.0、25.0、30.0℃时虎斑蝶卵的孵化率分别为86.36%、67.06%、75.00%、77.50%,幼虫的存活率分别为85.05%、84.59%、85.74%、80.78%,蛹的存活率分别为93.30%、94.12%、100.00%、100.00%。结果表明,17.5℃和30.0℃均不利于虎斑蝶幼期的存活,20.0～27.5℃是其幼期生长发育适宜的温度范围。长光照利于幼虫的存活,短光照利于卵的孵化和蛹的羽化;在17.5～30.0℃内,较高的温度利于蛹的羽化,而较低的温度利于卵的孵化和幼虫的存活;温度对虎斑蝶卵的孵化、幼虫的存活及蛹的羽化影响大于光周期;在养殖生产上,建议将幼期养殖温度控制在20.0～27.5℃,幼虫期饲养在长光照下为宜,卵和蛹期置于短光照下为宜。     

吉粳88高效再生体系的建立

以吉粳88为材料,通过对不同培养基和激素的筛选,确定最佳的再生体系。结果表明:NMB培养基为吉粳88最适的愈伤组织诱导培养基。通过L₉(3³)正交实验研究最适激素浓度配比,筛选出吉粳88愈伤组织诱导的最佳激素配比为2.0 mg/L 2,4-D+0.2 mg/L 6-BA+0.10 mg/L NAA。在添加2.0 mg/L 6-BA+0.5 mg/L NAA的NMB基本培养基条件下,吉粳88的分化率最高,成培苗率也最高。     

Optimising a clearance index based on neutral red as an indicator of physiological stress for bivalves

Neutral red is a weakly cationic dye that is soluble in water, has a low toxicity for almost all classes of organisms, and has been used as a histological and vital stain since the early twentieth century. Estimating the volume of water cleared of indicator material by suspension feeding bivalves (clearance or filtration rate) was one of the earliest applications of neutral red; however, less than thirty studies have applied this methodology since it was first described in 1954. The feeding/clearance rate is used as a sensitive indicator of physiological stress and is therefore an early-warning tool that is suitable for monitoring the ecological status of water bodies. The aim of our study was to optimise a clearance index based on neutral red solution by addressing the effect of i) the acidifying pH; ii) the holding temperature before spectrophotometric reading; and the time iii) before and iv) after the acidification of solutions of neutral red used to carry out clearance assays. Furthermore, as a case study we fine-tuned the clearance assay for the edible estuarine bivalve, Cerastoderma edule. The results showed that there were no statistical differences as regards the absorbance of neutral red solutions holding at 4 or 20 °C or a solution acidified between the ranges of pH 4–5. However, the absorbance significantly decreased as the pH increased to pH 6. The time before acidification had no significant effect on absorbance. Once the neutral red solution is acidified, the absorbance decreases over time, signifying that the absorbance should be read in the first 24 h. The concentration of neutral red used in the experiences should be sufficient to allow final concentrations of over 0.5 mg/L after the clearance period, since we observed that the sensitivity of this protocol decreased at low concentrations. In the case of C. edule, the optimum clearance conditions per individual were found to be 100 ml of 4 mg/L of neutral red dye during a 30 min period in dark conditions. A bioassay using a clearance index of C. edule based on this simple colorimetric technique would appear to be a potential tool for implementation in environmental monitoring programmes for water quality assessment in accordance with European directives. We trust that the new harmonised protocol will become a widely used and cost-effective means to monitor the clearance index as an indicator of physiological stress for bivalves.     

On the interpretation of some planktonology equations

Summary The concept of the mean value of a function is used to interpret some population-dynamics equations. The well-known formula for the per capita growth rate r gives a precise mean value for any (not only exponentially growing) populations. This result is used to derive the birth and death rate equations of Paloheimo (1974) with minimal initial limitations.Abbreviations t time - N number of animals - E number of eggs - r specific (i.e. per capita) population growth rate - b specific birth rate - d specific death rate - D duration of embryonic development     

转基因鱼构建模式的研究II.构建转基因鱼的几个影响因素(英文)

ＳｔｕｄｉｅｓｏｎＰａｔｅｒｎｏｆＰｒｏｄｕｃｉｎｇＴｒａｎｓｇｅｎｉｃＦｉｓｈＩ．ＳｅｖｅｒａｌＥｌｅｍｅｎｔｓＲｅｌａｔｅｄｔｏｔｈｅＥｓｔａｂｌｉｓｈｍｅｎｔｏｆＴｒａｎｓｇｅｎｉｃＦｉｓｈＬＩＵＣｈｕｎｑｉａｏ,ＺＨＡＮＧＹｏｎｇｚｈｏｎ...     

光合单位的周转率与叶片光合速率的关系

利用闪光技术,测得若干高等植物叶片的光合单位为 1450～2050 Chl/CO_2。在含O_2 2％及CO_2浓度和光通量密度都饱和的条件下,测得叶片的连续光合速率为25～70μmol CO_2 m~(-2) s~(-1)。从上述数据及叶片叶绿素含量计算,得叶片光合单位的周转率已达80～160次/s。这样的周转速率与Emerson当初用改变闪光间暗间隔而测到的光合单位周转时间相似(即<10 ms/次,或>100次/s),从而证实了光合单位的周转与光合速率直接有关。这样的速率可称之为叶片光合的理论速率。     

沙埋对两种一年生藜科植物存活及光合生理的影响

为了解沙埋对沙生植物存活的影响及其光合生理响应特征,比较不同藜科沙生植物耐沙埋能力及其光合响应,在内蒙古科尔沁沙地研究了沙米(Agriophyllum squarrosum)和大果虫实(Corispermum marocarpum)在不同沙埋深度下第5、10、15天的净光合速率、气孔导度、蒸腾速率、水分利用效率的变化,并于植物生长末期对存活率进行了测定。结果表明:沙米较大果虫实具有较强的耐沙埋能力,其中沙米幼苗最大耐沙埋深度超过苗高10 cm,大果虫实在埋深等于其苗高时全部死亡;随沙埋深度增加,沙米和大果虫实的存活率均显著下降,但沙米的下降幅度明显小于大果虫实;沙埋后,2种植物的气孔关闭或开放程度减小,通过降低蒸腾速率和提高水分利用效率来适应沙埋胁迫;随着沙埋胁迫的加剧,2种植物的净光合速率下降,表明沙埋胁迫对植物的光合作用破坏较大;相比于大果虫实,沙米对于沙埋胁迫有着更好的光合适应,随着胁迫的时间增加,其净光合速率有所恢复。