Smith D S, Brink D, del Castillo J
Proc Natl Acad Sci U S A. 1985 Mar;82(5):1555-7. doi: 10.1073/pnas.82.5.1555.
Electrical stimulation of the primary spines (greater than 10 cm long) of the tropical sea urchin Diadema antillarum elicits graded compound action potentials that are conducted at a constant speed of approximately equal to 27 cm/sec. Ion substitution experiments suggest that these are due to the summation of calcium spikes. Structural studies have revealed the presence of up to 21 regularly disposed nerves within the spine shaft, each nerve bundle including greater than 1000 neurites in the basal region, narrowing to slender groups of processes near the spine tip. The neurites in each nerve range in diameter from less than 0.1- approximately equal to 2 micron. Most appear to be distal processes of presumed sensory perikarya situated at the level of the tissue cone surrounding the spine base, or more proximally, although some neurites may arise from perikarya near the spine tip. These nerve tracts are thought to correspond to the nerve fibers described by Hamann [(1887) Jena Z. Naturwiss. 21, 114-176] almost a century ago in spines of Centrostephanus longispinus and, thus, to represent a long-neglected region of the echinoid nervous system.
对热带海胆马粪海胆（Diadema antillarum）的初级棘刺（长度大于10厘米）进行电刺激，会引发分级复合动作电位，其传导速度恒定，约为27厘米/秒。离子替代实验表明，这些电位是由钙峰的总和引起的。结构研究显示，棘刺轴内存在多达21条规则排列的神经，每个神经束在基部区域包含超过1000条神经突，在棘刺尖端附近变窄为细长的突起群。每条神经中的神经突直径范围从小于0.1微米到约2微米。大多数神经突似乎是假定的感觉神经核的远端突起，位于围绕棘刺基部的组织锥水平或更靠近近端的位置，不过有些神经突可能起源于棘刺尖端附近的神经核。这些神经束被认为与近一个世纪前哈曼[（1887年）《耶拿自然科学杂志》21卷，114 - 176页]在长棘冠海胆（Centrostephanus longispinus）的棘刺中描述的神经纤维相对应，因此代表了海胆纲神经系统中一个长期被忽视的区域。
