Dickinson Amanda J G, Croll Roger P
Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, B3H 4H7 Nova Scotia, Canada.
J Comp Neurol. 2003 Nov 10;466(2):197-218. doi: 10.1002/cne.10863.
Gastropods have been well studied in terms of early cell cleavage patterns and the neural basis of adult behaviors; however, much less is known about neural development in this taxon. Here we reveal a relatively sophisticated larval nervous system in a well-studied gastropod, Ilyanassa obsoleta. The present study employed immunocytochemical and histofluorescent techniques combined with confocal microscopy to examine the development of cells containing monoamines (serotonin and catecholamine), neuropeptides (FMRFamide and leu-enkephalin related peptides), and a substance(s) reactive to antibodies raised against dopamine beta-hydroxylase. Neurons were first observed in the apical organ and posterior regions during the embryonic trochophore stage. During later embryonic development neurons appeared in peripheral regions such as the foot, velum, and mantle and in the developing ganglia destined to become the adult central nervous system. In subsequent free-swimming veliger stages the larval nervous system became increasingly elaborate and by late larval stages there existed approximately 26-28 apical cells, 80-100 neurons in the central ganglia, and 200-300 peripherally located neurons. During metamorphosis some populations of neurons in the apical organ and in the periphery disappeared, while others were incorporated into the juvenile nervous system. Comparisons of neural elements in other molluscan larvae reveal several similarities such as comparable arrangements of cells in the apical organ and patterns of peripheral cells. This investigation reveals the most extensive larval nervous system described in any mollusc to date and information from this study will be useful for future experimental studies determining the role of larval neurons and investigations of the cellular and molecular mechanisms governing neural development in this taxon.
腹足纲动物在早期细胞分裂模式和成年行为的神经基础方面已经得到了充分研究；然而，对于这个分类群的神经发育了解得却少得多。在这里，我们揭示了一种经过充分研究的腹足纲动物——过时岩螺（Ilyanassa obsoleta）中相对复杂的幼虫神经系统。本研究采用免疫细胞化学和组织荧光技术，并结合共聚焦显微镜，来检查含有单胺（血清素和儿茶酚胺）、神经肽（FMRF酰胺和亮脑啡肽相关肽）以及对针对多巴胺β-羟化酶产生的抗体有反应的物质的细胞的发育情况。在胚胎担轮幼虫阶段，神经元首先在顶器和后部区域被观察到。在胚胎后期发育过程中，神经元出现在足部、膜和外套膜等周边区域以及注定会成为成年中枢神经系统的发育中的神经节中。在随后的自由游动面盘幼虫阶段，幼虫神经系统变得越来越复杂，到幼虫后期，大约有26 - 28个顶细胞、中枢神经节中有80 - 100个神经元以及周边有200 - 300个神经元。在变态过程中，顶器和周边的一些神经元群体消失了，而其他的则被纳入幼体神经系统。对其他软体动物幼虫神经元件的比较揭示了一些相似之处，例如顶器中细胞的可比排列和周边细胞的模式。这项研究揭示了迄今为止在任何软体动物中描述的最广泛的幼虫神经系统，并且这项研究的信息将有助于未来确定幼虫神经元作用的实验研究以及对控制这个分类群神经发育的细胞和分子机制的研究。
