The organization of the nervous system of the holothurian podia—the tentacles, papillae, and tube feet—is still poorly understood, which limits the development of functional studies. Knowledge of nitric oxide (NO) signaling in sea cucumbers is nonexistent, although it is known to play an important role in many essential biological functions, including neurotransmission, throughout the animal kingdom. The objective of this study was to characterize the holothurian podia in Holothuria arguinensis. To this end, we used classical histology, nitric oxide synthase (NOS) distribution, using NADPH‐diaphorase histochemistry and NOS immunostaining, and neuronal immunohistochemistry. Our results revealed an abundant distribution of NO in the nervous components of the holothurian podia, suggesting an important role for NO as a neuronal messenger in these structures. Nitrergic fibers were intensely labeled in the longitudinal nerve and the nerve plexus surrounding the stem, but were more weakly labeled in the mesothelium. NOS was also found in scattered cell bodies and abundant fibers in the podia terminal end (i.e., the discs in tentacles and tube feet, and the pointed conical structures in the papillae), with evident neuronal projections to the bud surface, especially in the tentacles. The podia terminal end was the most specialized area and was characterized by a specific nervous arrangement, consisting of a distinct nerve plate, rich in cells and fibers containing potential sensory cells staining positively for neuronal markers, which makes this the most likely candidate to be a chemosensory region and an important candidate for future exploration.

中文翻译：

---

一氧化氮合酶和其他神经元标记物在整oth足足中的定位和分布

对人足足神经系统的组织（触手，乳头和管脚）的了解仍然很少，这限制了功能研究的发展。尽管在整个动物界中，它在许多基本生物学功能（包括神经传递）中起着重要作用，但对海参中一氧化氮（NO）信号的了解尚不存在。这项研究的目的是表征霍罗索里亚（Hoholthuria arguinensis）的整足足。为此，我们使用经典的组织学，一氧化氮合酶（NOS）分布，NADPH-心肌黄酶的组织化学和NOS免疫染色以及神经元免疫组织化学。我们的研究结果表明，一氧化氮在全足神经的神经成分中分布丰富，这表明一氧化氮在这些结构中作为神经元信使具有重要作用。硝化纤维在纵神经和茎周围的神经丛中强烈标记，但在间皮中标记较弱。在足部末端的分散细胞体和丰富的纤维中（即触手和管脚中的椎间盘，以及乳头中的尖锥形结构）也发现了NOS，在芽表面，特别是在触手中有明显的神经元突起。 。