Tang Qing-Bo, Zhan Huan, Cao Huan, Berg Bente G, Yan Feng-Ming, Zhao Xin-Cheng
Department of Entomology, College of Plant Protection, Henan Agricultural University, Zhengzhou, Henan, China.
Department of Psychology, Neuroscience Unit, Norwegian University of Science and Technology, Trondheim, Norway.
PLoS One. 2014 Apr 16;9(4):e95401. doi: 10.1371/journal.pone.0095401. eCollection 2014.
Food selection behavior of lepidopteran larvae is predominantly governed by the activation of taste neurons present in two sensilla styloconica located on the galea of the maxilla. In this study, we present the ultrastructure of the sensilla styloconica and the central projection pattern of their associated receptor neurons in larvae of the heliothine moth, Helicoverpa armigera. By means of light microscopy and scanning electron microscopy, the previous findings of two morphologically fairly similar sensilla comprising a socketed conic tip inserted into a large peg were confirmed. However, the peg size of the medial sensillum was found to be significantly bigger than that of the lateral sensillum. The sensory neurons derived from each sensillum styloconicum were mapped separately using anterograde staining experiments combined with confocal laser-scanning microscopy. For determining the afferents' target regions relative to each other, we reconstructed the labeled axons and placed them into a common reference framework. The sensory axons from both sensilla projected via the ipsilateral maxillary nerve to the suboesophageal ganglion and further through the ipsilateral circumoesophageal connective to the brain. In the suboesophageal ganglion, the sensory projections targeted two areas of the ipsilateral maxillary neuropil, one located in the ventrolateral neuromere and the other adjacent to the neuromere midline. In the brain, the axon terminals targeted the dorso-anterior area of the ipsilateral tritocerebrum. As confirmed by the three-dimensional reconstructions, the target regions of the neural projections originating from each of the two sensilla styloconica were identical.
鳞翅目幼虫的食物选择行为主要由位于上颚外颚叶上的两个栓锥感器中的味觉神经元激活所控制。在本研究中，我们展示了棉铃虫（Helicoverpa armigera）幼虫栓锥感器的超微结构及其相关受体神经元的中枢投射模式。通过光学显微镜和扫描电子显微镜，证实了先前的发现，即两个形态相当相似的感器，由一个插入大栓体的带窝圆锥尖端组成。然而，发现内侧感器的栓体尺寸明显大于外侧感器。使用顺行染色实验结合共聚焦激光扫描显微镜分别绘制了源自每个栓锥感器的感觉神经元。为了确定传入神经相对于彼此的目标区域，我们重建了标记的轴突并将它们放入一个共同的参考框架中。来自两个感器的感觉轴突通过同侧上颚神经投射到咽下神经节，并进一步通过同侧围食管神经连接到脑。在咽下神经节中，感觉投射靶向同侧上颚神经纤维网的两个区域，一个位于腹外侧神经节段，另一个与神经节段中线相邻。在脑中，轴突终末靶向同侧后脑的背前部区域。通过三维重建证实，源自两个栓锥感器中每个感器的神经投射的目标区域是相同的。
