Friday Harbor Laboratories, University of Washington, Seattle, Washington, United States of America.
PLoS One. 2012;7(9):e44220. doi: 10.1371/journal.pone.0044220. Epub 2012 Sep 6.
Understanding of the echinoderm nervous system is limited due to its distinct organization in comparison to other animal phyla and by the difficulty in accessing it. The transparent and accessible, apodid sea cucumber Leptosynapta clarki provides novel opportunities for detailed characterization of echinoderm neural systems. The present study used immunohistochemistry against FMRFamide and histamine to describe the neural organization in juvenile and adult sea cucumbers. Histaminergic- and FMRFaminergic-like immunoreactivity is reported in several distinct cell types throughout the body of L. clarki. FMRFamide-like immunoreactive cell bodies were found in the buccal tentacles, esophageal region and in proximity to the radial nerve cords. Sensory-like cells in the tentacles send processes toward the circumoral nerve ring, while unipolar and bipolar cells close to the radial nerve cords display extensive processes in close association with muscle and other cells of the body wall. Histamine-like immunoreactivity was identified in neuronal somatas located in the buccal tentacles, circumoral nerve ring and in papillae distributed across the body. The tentacular cells send processes into the nerve ring, while the processes of cells in the body wall papillae extend to the surface epithelium and radial nerve cords. Pharmacological application of histamine produced a strong coordinated, peristaltic response of the body wall suggesting the role of histamine in the feeding behavior. Our immunohistochemical data provide evidence for extensive connections between the hyponeural and ectoneural nervous system in the sea cucumber, challenging previously held views on a clear functional separation of the sub-components of the nervous system. Furthermore, our data indicate a potential function of histamine in coordinated, peristaltic movements; consistent with feeding patterns in this species. This study on L. clarki illustrates how using a broader range of neurotransmitter systems can provide better insight into the anatomy, function and evolution of echinoderm nervous sytems.
棘皮动物神经系统的理解受到其与其他动物门明显不同的组织方式以及难以接近的限制。透明且易于接近的无柄海参 Leptosynapta clarki 为详细描述棘皮动物神经系统提供了新的机会。本研究使用针对 FMRFamide 和组氨酸的免疫组织化学方法描述了幼年和成年海参的神经组织。在 L. clarki 的整个身体中，报告了几种不同细胞类型的组氨酸能和 FMRF 酰胺样免疫反应性。FMRFamide 样免疫反应性细胞体位于触手、食管区域和靠近辐射神经索附近。触手中的感觉样细胞向口周神经环发送过程，而靠近辐射神经索的单极和双极细胞显示出与肌肉和体壁其他细胞密切相关的广泛过程。在位于触手、口周神经环和分布在整个身体上的乳突中的神经元体中鉴定出组氨酸样免疫反应性。触手细胞将过程发送到神经环，而体壁乳突细胞的过程延伸到表面上皮和辐射神经索。组胺的药理学应用产生了体壁的强烈协调的蠕动反应，表明组胺在摄食行为中的作用。我们的免疫组织化学数据为海参下神经和外神经之间的广泛连接提供了证据，这挑战了以前对神经系统子成分明确功能分离的观点。此外，我们的数据表明组胺在协调的蠕动运动中的潜在功能；与该物种的摄食模式一致。本研究表明，使用更广泛的神经递质系统如何能够更好地了解棘皮动物神经系统的解剖结构、功能和进化。
