Experimental study of enriched frozen diet on digestive enzymes and growth of juvenile cuttlefish Sepia officinalis L. (Mollusca Cephalopoda)

Hatchlings cuttlefish were reared in the laboratory from hatching until 30 days old, fed with live shrimp, frozen shrimp or fish oil-enriched frozen shrimp. Survival of cuttlefish fed with oil-enriched frozen shrimp was better than in animals receiving live shrimp. However, there was no difference with cuttlefish fed with frozen shrimp, even if survival of those receiving oil-enriched frozen shrimp was always higher all along the experiment. Lower survival in animals fed with live shrimp represented the problem of using such food and confirms the necessity to elaborate an artificial food. Utilization of artemia was detrimental to growth and induced low values of instantaneous growth rate (IGR) and conversion rate even after feeding cuttlefish with shrimp. Nevertheless, growth parameters evolutions generally corresponded to those observed by other researchers. The profile noticed at the end of the experiment is typically observed when cuttlefish acquire their adult digestive system. Main differences were observed between groups fed with live shrimp or oil-enriched frozen shrimp. Enrichment did not induce same growth as in cuttlefish receiving live prey. However, at 20 and 25 days after hatching (DAH), in cuttlefish fed with oil-enriched frozen shrimp, ration was lower for the same growth than in other groups.These data showed capacity of juvenile cuttlefish to adjust their digestive enzyme activities according to the diet and the stage of development. Indeed, chymotrypsin was strongly influenced by enrichment, while other enzymes showed difference between live and frozen preys. Trypsin exhibited regulation by diet after 20 DAH. Freezing seemed to delay development as acid phosphatases, characteristic of first stages of cuttlefish, had lower activity in cuttlefish fed with live shrimp at 10 DAH. Moreover, influence of the stage of development was strong as activities between 20 and 30 DAH were different in all groups. This was in relation with evolution of the digestive system. These data illustrated the difficulty to elaborate optimal diet as digestive system evolves.     

Intraspecific competition in tadpoles of Rana arvalis: does it matter in nature? A field experiment

Tadpole growth and development are easily affected by intraspecific competition in tank experiments, provided treatment density is sufficiently high. Is this a phenomenon also observed in nature? A pond was divided into four tadpole-proof sections. Each year for 8 years, all spawn laid by moorfrogs (Rana arvalis) in this pond was relocated to create relative spawn and tadpole densities of 1 : 4 : 1 : 4. No direct effect of the density manipulation on survival, tadpole size, and development and metamorph timing and size could be demonstrated. However, I also measured actual tadpole density during the time of development. Apart from the experimental density manipulation, this measure included effects of between-year variation in amount of spawn, natural tadpole mortality, and pond drying (which concentrated the tadpoles by decreasing the area of the pond sections). Actual density had limited but significant effects on tadpole size and development. I suggest that density regulation, acting on the tadpole stage, may be present in the population but was of less short-term importance than abiotic factors and, possibly, adult density regulation. Consequences of the findings for conservation are discussed.     

沙地柏对除叶干扰的生理和生长响应

为了研究沙地柏对模拟自然干扰的生理和生长响应,在毛乌素沙地对它进行了人为除叶为处理的模拟山羊啃食,虫害实验,结果表明,除叶干扰通过改变生理指标峰值出现的时间影响日动态,并显著影响生理指标的日平均值,除叶干扰对当年生枝生物量分配的影响不明显,但显著影响其生长特征。除叶干扰的最终效应受干扰方式和强度的双重制约,不同生理,生长指标对除叶干扰的敏感性存在差异,如净光合速率和腾速率,除干扰具有补偿效应,尤其是除老叶,因此适度剪除2年生以下枝条上的叶可促进当年生枝的生长和生物量积累。     

水面和水下长航对艇员肠道菌群影响的比较及意义探讨

比较研究和水下两种长期航行条件对航艇和核潜艇艇员肠道菌群的影响并对其意义进行初步探讨。结果显示两种长航条件均对人体肠道菌群产生显著影响,可打破肠道微生态平衡,但两者所致的肠道菌群构成变化的特点不同。提示不同长航条件可造成不同的微生态失调,需区别对待。     

培养基成分对口腔福赛类杆菌生长影响的研究

目的比较不同培养基成分对福赛类杆菌ATCC43037生长的影响,寻找一种有效促进福赛类杆菌生长的培养基.方法将福赛类杆菌ATCC430 37 接种到5种不同培养基(包括琼脂板和液体培养基)中,在厌氧培养箱内37℃厌氧培养7 d,观察平板上菌落生长情况,在λ=550 nm处每24 h测定液体培养菌液A值.细菌通过革兰染色和PCR法鉴定.结果1.生长在血平板上的福赛类杆菌ATCC43037菌落形态呈粉红色或白色小斑点状,在以BHI 为基础培养基中添加氯化血红素、维生素K3、N-乙酰胞壁酸的No2血琼脂培养基生长最好,而在无氯化血红素、维生素K3及血的No4琼脂板上不生长.2.福赛类杆菌ATCC43037在以TSB 为基础培养基中添加酵母提取物、植物蛋白胨、氯化血红素、维生素K3、N-乙酰胞壁酸和D TT的No1液体培养基生长最好,培养7 d后A值＞0.8,在缺乏N-乙酰胞壁酸的No5液体培养基中几乎不生长.3.菌落细菌革兰染色为G 梭状杆菌,PCR法鉴定为福赛类杆菌.结论福赛类杆菌在血平板和液体培养基中存在不同的生长特性,N-乙酰胞壁酸是福赛类杆菌在液体培养基中生长最重要的成分,DTT有益于细菌生长.     

3种林下灌木竹种地上竞争的可塑性响应

林下灌草层物种种群内竞争是森林生态系统发育和演替研究的重要组成部分。通过模拟去除边缘效应, 对3种赤竹属灌木竹种——铺地竹(Sasa argenteastriatus)、菲黄竹(S. auricoma)、菲白竹(S. fortunei)3种植物对地上竞争的可塑性响应研究。研究发现: (1)3种赤竹属竹种的垂直结构和器官(根、茎和叶)表征了在进化尺度上3种植物内源的相似性和表型可塑性差异; (2)根冠比表明在高密度条件下菲黄竹投入到地上部生物量大于低密度条件, 菲白竹类似, 铺地竹则相反, 3物种在向最大生长速率进化的过程中, 遇到生理(光合)和分配之间的交换关系而产生的矛盾选择; (3)菲黄竹与菲白竹较慢的光合速率, 表明在生理上已经对高密度处理产生可塑性变化, 并且这种可塑性是以缩短叶寿命为代价的。     

Influence of Environmental Factors on the Chemotaxis of Bradyrhizobium japonicum

Dependence of motility and chemotaxis was studied in two strains of Bradyrhizobium japonicum upon several environmental factors. In both strains, chemotaxis was found to increase with an increasing concentration of the attractant (glucose) to 5.5 × 10^–2 M. Both motility and chemotaxis reached their maximum in the two- to three-day cultures at neutral pH. The maximum motility of these bacteria occurred at 40°C. The maximum values of chemotaxis in these microorganisms were, however, observed at 20–25°C. Chemotaxis in acidic or alkaline media and at low temperatures was found to be markedly weaker. Nonoptimal values of these parameters in soil may be a limiting factor for the interaction of the given bacteria with soybean roots.     

Isolation and identification of a light-induced growth inhibitor in diffusates from blue light-illuminated oat (Avena sativa L.) coleoptile tips

The amounts of two growth inhibitors in diffusates from illuminatedhalves of phototropically stimulated oat (Avena sativa L.)coleoptile tips were larger than those from shaded halves. The less polarinhibitor was isolated from diffusates from oat coleoptile tips illuminatedwithblue light, and identified as uridine from ¹H NMR spectrum. Thedistribution of endogenous uridine in diffusates from the illuminated andshadedsides of coleoptile tips unilaterally exposed to blue light for 3, causing a first positive phototropic curvature, and fromdark-control tips, was determined using a physicochemical assay. The uridineconcentration was significantly higher in the diffusates from the illuminatedside than in those from the shaded side and the dark-control. Uridine inhibitedthe growth of etiolated oat coleoptile tips at concentrations of 30 and above. These results suggest that uridine plays a role inthe phototropism of oat coleoptiles.     

蓝尾石龙子的生长、两性异形及雌性繁殖

报道蓝尾石龙子（Eumeces elegans)的生长、两性异形和雌性繁殖,性成熟个体体色的两性差异显著,成年雄性体长、头长和头宽显著大于成年雌性,幼体体长生长率无显著的两性差异。成年雄体体长生长率显著大于成年雌体,因此,个体大小的两性异形是性成熟后发生的,体长小于50mm的幼体,头长和头宽无性差异;当体长大于50mm。雄性头长和头宽随体长的生长率显著大于雌性。并导致头部大小的两性异形,并随个体发育变得越来越显著,蓝尾石龙子产卵雌体的最小体长为69.3mm,大于此体长的雌体均年产单窝卵。窝卵数、窝卵重和平均卵重均与雌体体长呈正相关,平均值分别为6.4、2.783和0.554g。窝卵数与雌体产后状态无关,蓝尾石龙子雌体主要通过增加窝卵数和卵大小来增加繁殖输出。     

Dark Dune Spots: Possible Biomarkers on Mars?

Dark Dune Spots (DDSs) are transitional geomorphologic formations in the frost-covered polar regions of Mars. Our analysis of the transformations and arrangements of subsequent stages of DDSs into time sequence revealed their: (i) hole-like characteristics,(ii) development and formation from the bottom of the frosted layer till the disapperance of the latter, (iii) repeated (seasonal and annual) appearance in a pattern of multiple DDSs on the surface, and (iv) probable origin. We focused our studies on a model in which DDSs were interpreted as objects triggered by biological activity involvedin the frosting and melting processes. We discuss two competing interpretations of DDSs: development by defrosting alone, and by defrosting and melting enhanced by the activity of Martian Surface Organisms (MSOs). MSOs are hypothetical Martian photosynthetic surface organisms thought to absorb sunlight. As a result they warm up by late winter and melt the ice around them, whereby their growth and reproduction become possible. The ice cover above the liquid water lens harbouring the MSOs provides excellent heat and UV insulation, preventsfast evaporation, and sustains basic living conditions until the ice cover exists. When the frost cover disappears MSOs go to a dormant, desiccated state. We propose further studies to be carried out by orbiters and landers travelling to Mars and by analysis of partial analogues on earth.