Ultrastructure of the circumoral nerve ring and the radial nerve cords in holothurians (Echinodermata)
Ultrastructure of the circumoral nerve ring and the radial nerve cords in holothurians (Echinodermata)
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DOI：
10.1007/s00435-005-0010-9
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发表时间：
2006-03-01
期刊：
影响因子：
1
通讯作者：
Dolmatov, IY
中科院分区：
文献类型：
--
作者：
Mashanov, VS;Zueva, OR;Dolmatov, IY
本文报道了海参类神经组织的一个实例-黄刺真水蚤（Eupentacta fraudatrix）和光滑伪水蚤（Pseudocnus lubricus）的口周神经环和桡神经索。RNC由外神经层和内神经下层组成，它们通过短神经桥相互连接。口周神经环是纯外神经环。外神经和下神经成分都是上皮管，一侧有厚的神经上皮。薄的纤毛非神经元上皮补充神经上皮形成管，从而包围神经外膜和神经下管。整个外神经和下神经子系统通过连续的基底层与周围组织分离。桡神经的神经环、神经外段和神经下段都是由支持细胞和神经元组成的神经上皮。支持细胞被解释为神经胶质细胞。根据超微结构特征，可以区分三种类型的神经元：（1）假定的初级感觉神经元，其纤毛突出到神经外膜或神经下管;（2）非纤毛神经元，具有肿胀的粗面内质网池;（3）单纤毛神经元，嵌入神经纤维的主干。不同类型的突触发生在神经堆区域。它们符合经典化学突触的所有形态学标准。神经上皮细胞中存在着嗜酸性细胞。fraudatrix，但在P. lubricus缺席;他们的功能是未知的。假设覆盖外神经管和下神经管的非神经元上皮细胞与神经上皮的支持细胞属于相同的细胞类型。
The circumoral nerve ring and the radial nerve cords (RNCs) of Eupentacta fraudatrix and Pseudocnus lubricus (Holothuroidea) were examined as an example of holothurian nervous tissue. The RNC is composed of outer ectoneural and inner hyponeural layers, which are interconnected with one another via short neural bridges. The circumoral nerve ring is purely ectoneural. Both ectoneural and hyponeural components are epithelial tubes with a thick neuroepithelium at one side. A thin ciliated non-neuronal epithelium complements the neuroepithelium to form a tube, thereby enclosing the epineural and hyponeural canals. The whole of the ectoneural and hyponeural subsystems is separated from the surrounding tissue by a continuous basal lamina. The nerve ring and the ectoneural and hyponeural parts of the radial nerves are all neuroepithelia composed of supporting cells and neurons. Supporting cells are interpreted as being glial cells. Based on ultrastructural characters, three types of neurons can be distinguished: (1) putative primary sensory neurons, whose cilium protrudes into the epineural or hyponeural canal; (2) non-ciliated neurons with swollen rough endoplasmic reticulum cisternae; (3) monociliated neurons that are embedded in the trunk of nerve fibers. Different types of synapses occur in the neuropile area. They meet all morphological criteria of classical chemical synapses. Vacuolated cells occur in the neuroepithelium of E. fraudatrix, but are absent in P. lubricus; their function is unknown. The cells of the non-neuronal epithelia that overlie the ectoneural and hyponeural canals are hypothesized to belong to the same cell type as the supporting cells of the neuroepithelium.