Beetz M Jerome, El Jundi Basil, Heinze Stanley, Homberg Uwe
Fachbereich Biologie, Tierphysiologie, Philipps-Universität Marburg, D-35032, Marburg, Germany.
J Comp Neurol. 2015 Aug 1;523(11):1589-607. doi: 10.1002/cne.23736. Epub 2015 Feb 23.
Migrating desert locusts, Schistocerca gregaria, are able to use the skylight polarization pattern for navigation. They detect polarized light with a specialized dorsal rim area in their compound eye. After multistage processing, polarization signals are transferred to the central complex, a midline-spanning brain area involved in locomotor control. Polarization-sensitive tangential neurons (TB-neurons) of the protocerebral bridge, a part of the central complex, give rise to a topographic arrangement of preferred polarization angles in the bridge, suggesting that the central complex acts as an internal sky compass. TB-neurons connect the protocerebral bridge with two adjacent brain areas, the posterior optic tubercles. To analyze the polarotopic organization of the central complex further, we investigated the number and morphologies of TB-neurons and the presence and colocalization of three neuroactive substances in these neurons. Triple immunostaining with antisera against Diploptera punctata allatostatin (Dip-AST), Manduca sexta allatotropin (Mas-AT), and serotonin (5HT) raised in the same host species revealed three spatially distinct TB-neuron clusters, each consisting of 10 neurons per hemisphere: cluster 1 and 3 showed Dip-AST/5HT immunostaining, whereas cluster 2 showed Dip-AST/Mas-AT immunostaining. Five subtypes of TB-neuron could be distinguished based on ramification patterns. Corresponding to ramification domains in the protocerebral bridge, the neurons invaded distinct but overlapping layers within the posterior optic tubercle. Similarly, neurons interconnecting the tubercles of the two hemispheres also targeted distinct layers of these neuropils. From these data we propose a neuronal circuit that may be suited to stabilize the internal sky compass in the central complex of the locust.
迁徙的沙漠蝗虫,即群居飞蝗(Schistocerca gregaria),能够利用天空光偏振模式进行导航。它们通过复眼中专门的背缘区检测偏振光。经过多阶段处理后,偏振信号被传递到中央复合体,这是一个跨越中线的脑区,参与运动控制。中央复合体一部分的原脑桥中对偏振敏感的切向神经元(TB神经元)在桥中产生了优先偏振角的拓扑排列,这表明中央复合体起着内部天空罗盘的作用。TB神经元将原脑桥与两个相邻的脑区——后视结节相连。为了进一步分析中央复合体的偏振拓扑组织,我们研究了TB神经元的数量和形态,以及这些神经元中三种神经活性物质的存在和共定位情况。用针对在同一宿主物种中产生的双点大蠊咽侧体抑制素(Dip-AST)、烟草天蛾促咽侧体素(Mas-AT)和血清素(5HT)的抗血清进行三重免疫染色,揭示了三个空间上不同的TB神经元簇,每个半球各由10个神经元组成:簇1和簇3显示Dip-AST/5HT免疫染色,而簇2显示Dip-AST/Mas-AT免疫染色。根据分支模式可以区分出五种TB神经元亚型。与原脑桥中的分支区域相对应,这些神经元侵入后视结节内不同但重叠的层。同样,连接两个半球结节的神经元也靶向这些神经纤维网的不同层。根据这些数据,我们提出了一个神经元回路,它可能适合于稳定蝗虫中央复合体中的内部天空罗盘。