动物磁定向行为与磁感应机制研究进展

自然界中有许多动物(昆虫、鱼类、鸟类和啮齿类等)都可以感应地磁场并利用地磁场信息进行定向导航。然而,动物在定向导航过程中是如何感应地磁场信息目前尚无定论。目前科学家们也提出了一系列的磁感应假说,尽管每种磁感应假说都有相应的理论数据和实验数据的支持,但是没有任何一种磁感应假说可以很好地回答动物在磁感应过程中的所有问题。这主要归因于物种的多样性,不同动物可能会演化出不同的磁感应机制和定向导航策略。为了加深对动物磁定向行为与磁感应机制的理解,着重阐述了目前得到普遍认可的光依赖自由基对磁感应假说和非光依赖磁铁矿颗粒磁感应假说,以及基于Cryptochrome/MagR蛋白复合体的磁感应假说和电磁诱导磁感应假说;分析了不同动物在磁定向过程中磁感应机制差异的原因,以及磁感应行为在动物迁徙、觅食、归巢等生态行为中的作用;讨论了动物在不同环境中如何切换磁感应机制来进行定向导航;提出了动物在磁定向过程中需要磁感应系统与其他感官系统(如视觉、嗅觉、听觉等)的协同作用。研究不仅增强了对动物磁定向行为及磁感应机制的理解,还提高了对动物在复杂的自然环境中如何利用地磁场信息进行定向导航的认知。此外,研究深入剖析了动物磁定向行为及磁感应机制研究领域所面临的问题与挑战,并据此提出磁感应研究应加强跨学科合作,尤其是与动物行为学、分子生物学、生物电磁学、生物物理学、神经生物学和系统生物学等多学科多领域的交叉融合,将有助于推动磁感应行为与机制研究的深入与拓展。同时,通过不断探索与创新,有望揭示更多关于动物定向导航的奥秘,并为生态保护、生物导航技术等领域的发展提供新的思路与方法。     

动物地磁导航机制研究进展

地磁场是地球重要的物理场,它不仅能保护地球生物免受太阳风及其他宇宙射线的伤害,阻挡地球生命赖以生存的大气圈和水圈被剥蚀,为地球生物提供一个温和的生存进化环境,而且其强度、偏角和倾角能为动物迁徙提供定位导航参考。目前,行为学研究已经发现许多鸟类、爬行类、两栖类、哺乳类等动物都能够利用地磁场导航。动物感知地磁场的磁感受器(magnetoreceptor)、磁信息的感知机制和信号传递通路一直是动物地磁导航研究的焦点和难点,但目前对它们的了解并不十分清楚。基于国内外学者最近的研究成果,本文首先介绍三种主要的磁感知机制及其相应的证据:电磁感应、基于光受体的磁感知及基于磁铁矿纳米颗粒的磁感知。其次,总结鸟类基于光受体和磁铁矿纳米颗粒的磁感知神经通路和相应的磁信息响应脑区:(1)眼睛视网膜上光依赖的磁感受器——隐花色素通过视觉通路与大脑联系获取准确方向信息;(2)上喙或内耳中的磁铁矿纳米颗粒磁感受器,通过三叉神经或内耳听壶传入神经将感知的磁场强度信息传至脑干前庭区域,获得\"导航图\"信息。最后,简要总结近年来哺乳动物地磁导航的研究进展,并指出动物地磁导航研究当前亟待解决的几个重要科学问题。     

Pollination of strawberry by the stingless bee,Trigona minangkabau,and the honey bee,Apis mellifera: An experimental study of fertilization efficiency

To know basic information about the stingless bee, Trigona minangkabau, and the European honey bee, Apis mellifera, as pollinator of strawberry, we set three greenhouse areas: the honey bee introduced area, the stingless bee introduced area and the control area. Foraging and pollination efficiencies of the two bee species were studied comparatively. During the experimental period (10 days), the stingless bee foraged well and the nest weight did not change, though the honey bee often foraged inefficiently and the nest weight decreased by 2 kg. The average nectar volume of a flower was lower in the honey bee area (0.02 μl) and nearly the same in the other two areas (0.1 μl). We make a numerical model to describe pollination and fertilization process. This model shows that one visit of the honey bee pollinated 11% of achenes and one visit of the stingless bee did 4.7% on average and that 11 visits of the honey bee or 30 visits of the stingless bee are required per flower to attain normal berry (fertilization rate, 87%). In this study, the rate of deformed berries in the stingless bee area (73%) was lower than that of the control area (90%), but higher than that of the honey bee area (51%). From our numerical model, we conclude the stingless bee could pollinate strawberry as well as the honey bee if we introduced 1.8 times of bees used in this experiment.     

A new species of Syntretus Foerster (Hymenoptera: Braconidae: Euphorinae), a parasitoid of the stingless bee Trigona carbonaria Smith (Hymenoptera: Apidae: Meliponinae)

A new species of euphorine braconid, Syntretus trigonaphagus sp. nov., is described and illustrated. This is the first Australian Syntretus species to be described and the first record of braconids parasitising Trigona Jurine stingless bees. Egg-laying by adults and emergence of larvae from the host Trigona carbonaria is detailed. A 12S ribosomal rRNA gene fragment was sequenced to confirm the association of larvae and adults of the wasp parasitoid.     

Tetragonisca guard bees interpret expanding and contracting patterns as unintended displacement in space

Guard bees of the stingless bee Tetragonisca angustula (Apidae: Meliponinae) hover in stable positions in front of the nest to protect the flight corridor leading to the nest entrance against insect intruders. To unravel the visual control of station keeping, we exposed these hovering guards to expanding and contracting patterns at the nest front. The bees fly away from an expanding pattern and towards the centre of a contracting pattern along a line connecting their initial position and the centre of expansion regardless of where in the visual field they view the pattern. The response of bees to a spinning radial pattern is different: they fly parallel to the pattern, up and down or forward and backward depending on whether they initially hover to the side, above or below the centre of rotation. The bees respond to horizontal and to vertical expansion and contraction. They also adjust their distance relative to a rotating spiral which produces a realistic flow field and thus allowed us to test to what extent the bees minimize image motion speed. We find that guard bees indeed move in the appropriate direction to minimize the image motion speed they experience. A comparison of bees hovering at different distances from the nestfront at the onset of pattern motion and experiencing very different image velocities shows that the dynamics of the reaction is quite uniform. At the pattern velocities tested, we did not find evidence that guard bees use image motion to control their flight speed. The bees' response rather suggests that the underlying mechanism might be insensitive to the size of motion vectors. Accepted: 2 April 1997     

Stingless Bee Antennae: A Magnetic Sensory Organ?

Magnetic material in the body parts of the stingless bee Schwarziana quadripunctata, heads, pairs of antennae, thorax and abdomens, were investigated by SQUID magnetometry and Ferromagnetic Resonance (FMR). The saturation, J_s and remanent, J_r, magnetizations and coercive field H_c are determined from the hysteresis curves. From H_c and J_r/J_s the magnetic particle sizes are estimated. The J_s and the FMR spectral absorption areas yield 23±3%, 45±5%, 15±2% and 19±4% magnetic material contributions of head, pair of antennae, thorax and abdomen, respectively, similar to those observed in the migratory ant Pachycondyla marginata. This result is discussed in light of the hypothesis of antennae as a magnetosensor structure.     

无刺蜂的研究概况与展望

无刺蜂是重要的资源昆虫,在授粉、药用、工业原料等方面有着利用价值。目前,国内外对无刺蜂的研究的领域和方向主要有种类分布、生物学特征、经济价值、饲养管理技术、分子研究等方面。为了更好地对无刺蜂展开研究,充分利用无刺蜂的各种价值,笔者综述了国内外关于无刺蜂的研究进展,分析了国内无刺蜂的研究现状和不足,并对今后的发展趋势进行了展望。     

Induction of Multinuclear Cells in the Apical Meristems of Allium cepa by Geomagnetic Field Outrages

This paper is a result of a long-term study of the apical meristems of the Allium cepa L. seedlings against a background of naturally changing geomagnetic field. Multinuclear cells, large cells with large nuclei, and giant cells with giant nuclei were detected. Changes in cellular structures were revealed, and the time-course of this process was followed. Changes in the cellular structure of meristems were correlated with the fluctuations of magnetic field of the Earth. The experiments conducted with in vitro culture of apical meristems showed that the observed changes were regulated on the local level.     

Exposure of Postnatal Rats to a Static Magnetic Field of 0.14 T Influences Functional Laterality of the Hippocampal High-Affinity Choline Uptake System in Adulthood; <Emphasis Type="Italic">In vitro</Emphasis> Test with Magnetic Nanoparticles

Our previous experiments indicated an age- and sex-dependent functional lateralization of a high-affinity choline uptake system in hippocampi of Wistar rats. The system is connected with acetylcholine synthesis and also plays a role in spatial navigation. The current study demonstrates that a single in vivo exposure of 7- or 14-day-old males to a static magnetic field of 0.14 T for 60–120 min evokes asymmetric alterations in the activity of carriers in adulthood. Namely, the negative field (antiparallel orientation with a vertical component of the geomagnetic field) mediated a more marked decrease in the right hippocampus. The positive field (parallel orientation) was ineffective. Moreover, differences between the carriers from the right and the left hippocampi were observed on synaptosomes pretreated with superparamagnetic nanoparticles and exposed for 30 min in vitro. The positive field enhanced more markedly the activity of carriers from the right hippocampus, the negative that from the left hippocampus, on the contrary. Our results demonstrate functionally teratogenic risks of the alterations in the orientation of the strong static magnetic field for postnatal brain development and suggest functional specialization of both hippocampi in rats. Choline carriers could be involved as secondary receptors in magnetoreception through direct effects of geomagnetic field on intracellular magnetite crystals and nanoparticles applied in vivo should be a useful tool to evaluate magnetoreception in future research.     

Detection of diploid males in a natural colony of the cleptobiotic bee Lestrimelitta sp (Hymenoptera, Apidae)

When working at quantifying the genome size of stingless bees, it was observed that males of Lestrimelitta sp possessed the same amount of nuclear DNA as the females. Thus, we used flow cytometry (FCM) and cytogenetic analysis to confirm the ploidy of these individuals. The males analyzed proved to be diploid, since, through cytometric analysis, it was demonstrated that the mean genome size of both males and females was the same (C = 0.463 pg), and, furthermore, cytogenetic analysis demonstrated that both had 2n = 28 chromosomes.     

Electric-field ion cyclotron resonance

We consider the possibility that DC magnetic fields can interact in a resonant manner with endogenous AC electric fields in biological systems. Intrinsic electric-field ion cyclotron resonance (ICR) interactions would be more physically credible than models based on external AC magnetic fields and might be expected as an evolutionary response to the long-term constancy of the geomagnetic field. Bioelectromagnetics 17:85–87, 1997. © 1997 Wiley-Liss, Inc.