Light-dependent magnetoreception in birds: interaction of at least two different receptors

Passerine migrants require light from the blue-green part of the spectrum for magnetic compass orientation; under yellow light, they are disoriented. European robins tested under a combination of yellow light and blue or green light showed a change in behavior, no longer preferring their seasonally appropriate migratory direction: in spring as well as in autumn, they preferred southerly headings under blue-and-yellow and northerly headings under green-and-yellow light. This clearly shows that yellow light is not neutral and suggests the involvement of at least two types of receptors in obtaining magnetic compass information, with the specific interaction of these receptors being rather complex.     

Magnetic compass orientation of European robins under 565 nm green light

European robins tested under monochromatic green light with a peak wavelength of 565 nm at an intensity of 2.1 mW m^-2 in the local geomagnetic field preferred their migratory direction, heading southward in autumn and northward in spring. Inverting of the vertical component of the magnetic field caused the robins to reverse their headings, indicating that the birds used a magnetic inclination compass to locate their migratory direction. The behavior recorded under green light at an intensity of 2.1 mW m^-2 is thus not different from that previously recorded under "white" light; it represents normal migratory orientation.     

Light-dependent magnetic compass in Iberian green frog tadpoles

Here, we provide evidence for a wavelength-dependent effect of light on magnetic compass orientation in Pelophylax perezi (order Anura), similar to that observed in Rana catesbeiana (order Anura) and Notophthalmus viridescens (order Urodela), and confirm for the first time in an anuran amphibian that a 90° shift in the direction of magnetic compass orientation under long-wavelength light (≥500 nm) is due to a direct effect of light on the underlying magnetoreception mechanism. Although magnetic compass orientation in other animals (e.g., birds and some insects) has been shown to be influenced by the wavelength and/or intensity of light, these two amphibian orders are the only taxa for which there is direct evidence that the magnetic compass is light-dependent. The remarkable similarities in the light-dependent magnetic compasses of anurans and urodeles, which have evolved as separate clades for at least 250 million years, suggest that the light-dependent magnetoreception mechanism is likely to have evolved in the common ancestor of the Lissamphibia (Early Permian, ~294 million years) and, possibly, much earlier. Also, we discuss a number of similarities between the functional properties of the light-dependent magnetic compass in amphibians and blue light-dependent responses to magnetic stimuli in Drosophila melanogaster, which suggest that the wavelength-dependent 90° shift in amphibians may be due to light activation of different redox forms of a cryptochrome photopigment. Finally, we relate these findings to earlier studies showing that the pineal organ of newts is the site of the light-dependent magnetic compass and recent neurophysiological evidence showing magnetic field sensitivity in the frog frontal organ (an outgrowth of the pineal).     

光照度对水华鱼腥藻细胞比重与藻丝长度的影响研究

为深入探索可获得光资源量(light availability)与水华鱼腥藻(Anabaena flos-aquae)浮沉关键因子——细胞比重、藻丝长度,以及水华鱼腥藻沉降损失的关系,开展了纯培养试验.在温度(25±1)℃,光照度分别为100,500,1000,3000,5000lx的条件下,培养时间35d,结果显示:在1~10d内鱼腥藻细胞比重随光照度增大而增大,在10d左右达到最大值,随后各光照组下鱼腥藻细胞比重较稳定且相差不大;光照越强,水华鱼腥藻的藻丝越短,其变化趋势是先增大到最大值再减小;光照越强,水华鱼腥藻的藻丝长度越快增大到最大值;实验结束时高光照度下水华鱼腥藻沉降损失比率较小,均低于10%,低光照下水华鱼腥藻沉降性能较好,最高可达到57.3%.实验结果表明:可获得光资源量下降直接影响鱼腥藻比重和藻丝长度并进一步导致鱼腥藻的沉降损失比率增大,这为持续型垂直混合导致蓝藻消亡的原因提供了新解释.     

Behavioural evidence of magnetoreception in dolphins: detection of experimental magnetic fields

Magnetoreception, meaning the perception of magnetic fields, is supposed to play an important role for orientation/navigation in some terrestrial and aquatic species. Although some spatial observations of free-ranging cetaceans’ migration routes and stranding sites led to the assumption that cetaceans may be sensitive to the geomagnetic field, experimental evidence is lacking. Here, we tested the spontaneous response of six captive bottlenose dolphins to the presentation of two magnetized and demagnetized controlled devices while they were swimming freely. Dolphins approached the device with shorter latency when it contained a strongly magnetized neodymium block compared to a control demagnetized block that was identical in form and density and therefore undistinguishable with echolocation. We conclude that dolphins are able to discriminate the two stimuli on the basis of their magnetic properties, a prerequisite for magnetoreception-based navigation.     

Daytime light intensity affects seasonal timing via changes in the nocturnal melatonin levels

Daytime light intensity can affect the photoperiodic regulation of the reproductive cycle in birds. The actual way by which light intensity information is transduced is, however, unknown. We postulate that transduction of the light intensity information is mediated by changes in the pattern of melatonin secretion. This study, therefore, investigated the effects of high and low daytime light intensities on the daily melatonin rhythm of Afro-tropical stonechats (Saxicola torquata axillaris) in which seasonal changes in daytime light intensity act as a zeitgeber of the circannual rhythms controlling annual reproduction and molt. Stonechats were subjected to light conditions simulated as closely as possible to native conditions near the equator. Photoperiod was held constant at 12.25 h of light and 11.75 h of darkness per day. At intervals of 2.5 to 3.5 weeks, daytime light intensity was changed from bright (12,000 lux at one and 2,000 lux at the other perch) to dim (1,600 lux at one and 250 lux at the other perch) and back to the original bright light. Daily plasma melatonin profiles showed that they were linked with changes in daytime light intensity: Nighttime peak and total nocturnal levels were altered when transitions between light conditions were made, and these changes were significant when light intensity was changed from dim to bright. We suggest that daytime light intensity could affect seasonal timing via changes in melatonin profiles. Professor Dr. E. Gwinner died on 07 September 2004.     

光照强度和磷浓度对寡枝刚毛藻生长的影响

在利用沉水植被对湖泊进行生态修复过程中,当营养盐有所降低,水体透明度增加有利于沉水植物生长时,丝状绿藻——刚毛藻会大量生长,从而影响生态修复效果.为了研究光照强度和磷浓度对寡枝刚毛藻(Cladophora oligoclona)生长的影响,本实验用含有不同磷浓度(0.005,0.02,0.1,0.6mg/L)的BBM培养基,在不同光照强度[10,30,50μmol/(m2·s)]下培养寡枝刚毛藻16d.结果发现,在光照强度为10μmol/(m2·s),初始P浓度0.1mg/L以上时,刚毛藻鲜重增加(约0.05g),其余处理条件下,刚毛藻鲜重均减少,其中光强为50μmol/(m2·s),初始磷浓度为0.005mg/L时,刚毛藻鲜重减少量最大(约0.49g).叶绿素荧光参数Fv/Fm值的变化表现为光强越大,Fv/Fm的值越低.在光强为10μmol/(m2·s)时,Fv/Fm值在0.75左右.光强为50μmol/(m2·s)时,Fv/Fm值仅为0.3.在相同光强下,不同磷浓度对Fv/Fm值变化无显著影响.相对于磷浓度对刚毛藻生长的影响,光强对刚毛藻的生长影响更大,且高光强不利于刚毛藻的生长.     

基于细胞尺度的光照对四尾栅藻生长的影响

以四尾栅藻（Scenedesmus quadricauda）为研究对象,采用平行平板流动腔装置,基于计算机视觉的藻细胞动态生长观察方法,从单细胞尺度研究不同光照强度对四尾栅藻藻细胞生长的影响.成功建立了四尾栅藻个体生长曲线模型,模型拟合效果良好.结果表明：在8000lux光照强度下,藻细胞的体积最大比生长速率最大,即四尾栅藻生长的最适光照强度为8000lux;适宜的光照条件可以增加藻细胞分裂时的大小,小于8000lux时,藻细胞分裂体积随着光照强度的增加而增加,大于8000lux时,藻细胞分裂时体积反而越来越小;较高的光照强度还有利于藻细胞适应新的环境,减少藻细胞复苏时间.     

低光照度对源水中铜绿微囊藻增殖的抑制作用

研究了不同光照度条件下铜绿微囊藻在源水中的增殖趋势.结果表明,以灭活源水为培养基,培养周期13d,在23℃时,当光照度≤500lx,铜绿微囊藻生长受到明显的抑制,其比增值速率(μ)为负数,呈衰亡趋势;在28℃时,当光照度≤200lx,最大藻现存量较4300lx时削减70%以上.以未灭活源水为培养基,23℃时,发现铜绿微囊藻逐渐消亡,这与微型浮游动物的大量出现有关.     

基于细胞尺度的光照对四尾栅藻生长的影响

以四尾栅藻（Scenedesmus quadricauda）为研究对象,采用平行平板流动腔装置,基于计算机视觉的藻细胞动态生长观察方法,从单细胞尺度研究不同光照强度对四尾栅藻藻细胞生长的影响.成功建立了四尾栅藻个体生长曲线模型,模型拟合效果良好.结果表明：在8000lux光照强度下,藻细胞的体积最大比生长速率最大,即四尾栅藻生长的最适光照强度为8000lux;适宜的光照条件可以增加藻细胞分裂时的大小,小于8000lux时,藻细胞分裂体积随着光照强度的增加而增加,大于8000lux时,藻细胞分裂时体积反而越来越小;较高的光照强度还有利于藻细胞适应新的环境,减少藻细胞复苏时间.     

上海市绿地植被的吸热降温效益评估

城市绿地夏季高温时具有明显降温作用。但现有研究侧重降温效应观测及其影响因子解析,而对绿地降温效益与人居环境需求的空间一致性鲜有研究。以上海市为例,基于高分卫星影像与样地观测数据,采用植被蒸腾吸热经验模型评估了城市绿地夏季降温效益,并利用GIS空间分析技术量化了绿地降温效益与空气温度及人口分布的空间耦合程度。结果表明:2017年上海城市绿地面积为10.45万hm ²,夏季（6-9月）绿地植被吸热量可达8.49×10 ¹⁵ J,相当于节约夏季空调降温的经济价值为14.57亿元,其中46%和33%的绿地降温效益来自阔叶林与混交林;浦东新区、崇明区和奉贤区的绿地植被合计贡献了67%的降温效益,但虹口、黄浦、徐汇等中心城区绿地的单位面积降温效益较高。更需关注的是,绿地植被降温效益与人居环境需求表现出局部地区的空间不一致,其中28.62%的地区植被降温效益与空气温度处于低耦合状态,7.31%的地区植被降温效益与人口密度为低耦合水平,且均集中分布在中心城区。因此,重点提升中心城区绿地植被降温功能,并规划建设周边绿地降温效益的空间辐射通道,是上海城市生态空间优化的重要方向。     

环境规制视角下制造业绿色转型对能源强度的影响

基于Super-SBM及动态面板门槛模型,系统分析中国制造业行业绿色转型异质性结构,并从环境规制视角探析制造业绿色转型对于其行业能源强度的影响效应.研究发现：中国制造业绿色转型并没有实现（平均值为-0.1637）,且行业间差异显著,其转型过程呈现明显波动特征.有趣的是,中国制造业绿色转型对于能源强度的作用存在显著的环境规制异质门槛效应：较低程度的环境规制并不利于促使制造业绿色转型降低能源强度.而随着环境规制强度的提高并突破“临界点”,在一定程度上有效增强了制造业绿色转型的影响作用,进而推动能源强度的降低.     

中国省域碳排放强度的集聚效应和辐射效应研究

估算了中国1997—2013年30个省(市、自治区)的碳排放强度数据,并利用全局Moran's Ⅰ指数、局域Moran's Ⅰ指数以及莫兰散点图从集聚效应和辐射效应两个角度考察了我国区域碳排放强度空间分布特征.结果显示:1集聚效应:我国省域碳排放强度具有明显的空间集聚特征,碳排放强度水平相似区域倾向于相邻分布;另外,碳排放强度空间分布呈现不断优化的趋势,即"低-低"集聚不断增加,"高-高"集聚逐渐减少.2辐射效应:内蒙古、宁夏和山西等省对周边地区的碳排放强度具有明显的正向辐射效应,广东、福建和浙江等省对周边地区碳排放强度具有明显的负向辐射效应.最后,据此提出政策建议.     

A novel concept of Fe-mineral-based magnetoreception: histological and physicochemical data from the upper beak of homing pigeons

Animals make use of the Earth’s magnetic field for navigation and regulation of vegetative functions; however, the anatomical and physiological basis for the magnetic sense has not been elucidated yet. Our recent results from histology and X-ray analyses support the hypothesis that delicate iron-containing structures in the skin of the upper beak of homing pigeons might serve as a biological magnetometer. Histology has revealed various iron sites within dendrites of the trigeminal nerve, their arrangement along strands of axons, the existence of three dendritic fields in each side of the beak with specific 3D-orientations, and the bilateral symmetry of the whole system. Element mapping by micro-synchrotron X-ray fluorescence analysis has shown the distribution of iron and its quantities. Micro-synchrotron X-ray absorption near-edge-structure spectroscopy has allowed us to unambiguously identify maghemite as the predominating iron mineral (90 vs 10% magnetite). In this paper, we show that iron-based magnetoreception needs the presence of both of these iron minerals, their specific dimensions, shapes, and arrangements in three different subcellular compartments. We suggest that an inherent magnetic enhancement process via an iron-crusted vesicle and the attached chains of iron platelets might be sufficient to account for the sensitivity and specificity required by such a magnetoreceptor. The appropriate alignment between the Earth’s magnetic field and the maghemite bands would induce a multiple attraction of the magnetite bullets perpendicular to the membrane, thus, triggering strain-sensitive membrane channels and a primary receptor potential. Due to its 3D architecture and physicochemical nature, the dendritic system should be able to separately sense the three vector components of the Earth’s local field, simultaneously—allowing birds to detect their geographic position by the magnetic vector, i.e., amplitude and direction of the local magnetic field, irrespective of the animal’s posture or movement and photoreception.     

Eutrophication and algal blooms in channel type reservoirs: A novel enclosure experiment by changing light intensity

To explore eutrophication and algal bloom mechanisms in channel type reservoirs, a novel enclosure experiment was conducted by changing light intensity (LI) in the Daning River of the Three Gorges Reservoir (TGR). Square enclosures (side 5.0 m) were covered on the surface with shading materials of different thickness, and with their bases open to the river. Changes and characteristics of the main eutrophication factors under the same water quality and hydrodynamic conditions but different LI were evaluated. All experimental water samples were neutral and alkalescent, with high nitrogen and phosphate concentrations, low potassium permanganate index, stable water quality, and different LI. At the same water depth, LI decreased with increasing shade material, while dissolved oxygen and water temperature were both stable. The growth peak of phytoplankton was with light of 345-4390 lux underwater or 558-7450 lux above the water surface, and water temperature of 25.6-26.5℃. Algae were observed in all water samples, accounting for 6 phylum and 57 species, with algal density changing frequently. The results showed that significantly strong or weak light was unfavorable for phytoplankton growth and the function together with suitable temperature and LI and ample sunshine encouraged algal blooms under the same water quality and hydrodynamic conditions. Correlation analysis indicated that algae reduced gradually lengthwise along water depth in the same enclosure while pH became high. The power exponent relationship between chlorophyll a (Chl-a) and LI was found by curve fitting, that is Chl-a = K(LI)ⁿ.     

氮素形态与光强对苗期黄瓜吸收累积菲的影响研究

采用营养液培养的方法研究了不同形态氮素(NH4 -N、NO3 -N)和光强对菲胁迫条件下黄瓜幼苗生长及光合特性的影响.结果表明:①与供NO3- -N营养相比,供NH4 -N营养可同时增强黄瓜幼苗的抗菲胁迫及耐弱光的能力;②以NH4 -N为营养的黄瓜吸收的菲不仅运输至叶片的比例相对较低,而且运输至新生叶片的比例也相对较少,相对降低了新生叶中的菲累积,因而使得以NH4 -N为营养的黄瓜新生叶片维持了相对较大的光合面积和较高的光合速率.由此可见,与NO3- -N营养相比,NH4 -N营养能改善黄瓜在菲胁迫环境中的生长状况,尤其在弱光条件下,这种现象更加明显.     

The relationship between light intensity and nutrient uptake kinetics in six freshwater diatoms

In order to find effective measures to control diatom blooms, a better understanding of the physiological characteristics of nutrient uptake in diatoms is needed. A study of P and Si-uptake kinetics for diatom species from two light regimes was conducted at low (LL), moderate (ML) and high light intensities (HL) (2, 25 and 80 μmol photons/(m²·sec)), respectively. The results showed that P uptake of diatoms was heavily influenced by historic light regimes. P affinity changed with growth and photosynthetic activity. The lowest half saturation constant for P uptake (K_m(P)) was under HL for high-light adapted diatoms while the lowest half-saturation constant for low-light adapted diatoms was observed under LL. The Si half-saturation constant (K_m(Si)) increased with increasing light intensities for pennate diatoms but decreased for centric diatoms. Diatom volumes were correlated with the maximum Si uptake rates (V_m(Si)) at HL and K_m(Si) at ML and HL for six diatom species. Our results imply that when we assess the development of diatom blooms we should consider light intensity and cell volume in addition to ambient Si or P concentration. The relationship between light intensity and P-uptake suggests that we can find suitable methods to control diatom blooms on the basis of reducing phytoplankton activity of P-uptake and photosynthesis simultaneously.