Holland N D, Grimmer J C
Cell Tissue Res. 1981;214(1):207-17. doi: 10.1007/BF00235158.
Crinoid cirri are jointed appendages that can slowly bend and straighten. The structures causing each cirrus to move have not been identified unequivocally by light microscopy; therefore, we examined them by electron microscopy. No muscle cells were found, but a probable contractile apparatus was demonstrated in the cytoplasm of epithelial cells lining the oral and aboral coeloms running the length of the cirrus. The presumed contractile apparatus is a bundle of 5 nm filaments oriented parallel to each other and to the long axis of the appendage. We have proposed that contractile shortening of the coelomic epithelia bends the cirrus in an aboral direction, since the fulcral articulations of the skeletal ossicles are oral to the contractile tissue; this active bending is presumably opposed by an elasticity of the oral ligaments, which seem to straighten the cirrus. It is possible that ligaments of the cirrus may undergo neurosecretion-mediated changes in consistency that could lock the appendage into a rigid state; however, active contraction by the ligaments appears unlikely.
海百合的触须是有关节的附属物，能够缓慢弯曲和伸直。通过光学显微镜尚未明确鉴定出导致每条触须移动的结构；因此，我们通过电子显微镜对其进行了检查。未发现肌肉细胞，但在沿着触须长度延伸的口侧和反口侧体腔的上皮细胞胞质中证实了一种可能的收缩装置。推测的收缩装置是一束5纳米的细丝，它们彼此平行且与附属物的长轴平行排列。我们提出，体腔上皮的收缩性缩短会使触须向反口方向弯曲，因为骨骼小骨的支点关节位于收缩组织的口侧；这种主动弯曲大概受到口侧韧带弹性的对抗，口侧韧带似乎能使触须伸直。触须的韧带可能会经历神经分泌介导的稠度变化，从而将附属物锁定在刚性状态；然而，韧带的主动收缩似乎不太可能。
