Reed Christopher G, Ninos John M, Woollacott Robert M
Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755.
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138.
J Morphol. 1988 Aug;197(2):127-145. doi: 10.1002/jmor.1051970202.
The ultrastructure of ciliated sensory and effector organs has been examined by light microscopy and by scanning and transmission electron microscopy in larvae of the cellularioid cheilostome, Bugula stolonifera. The larval surface is formed by a mosaic of ciliary fields, each distinctive in organization and function. The most extensive ciliary field consists of the motile cilia of the corona, which collectively constitute the primary larval locomotory organ and form most of the larval surface. The corona is innervated basally by a nerve ring that circumscribes the larval equator. A circular field of immotile shorter cilia at the aboral pole arise from bands of radial cells in the apical disc. The radial ciliated cells form chemical synapses with underlying nerves of the paired aboral nerve cords, which extend to an equatorial nerve plexus on the median anterior side of the larva, beneath the pyriform organ. The pyriform organ is a complex of ciliated and glandular regions aligned along the anterior midline of the larva. It consists of, in aboral to oral sequence: the superior glandular field, the vibratile plume, the inferior glandular field, and the ciliated cleft. The vibratile plume is distinctive from the surrounding ciliation by its length and pattern of beating. It consists of four bundles of cilia approximately 64 μm long that beat rhythmically in synchrony into the ciliated cleft. Each bundle of cilia arises from a single cell which is further distinguished by apical pits of stout microvilli. The glandular fields and the vibratile plume are bordered by a variety of previously undescribed ciliated cells, longitudinal myoepithelial cells, and a pair of antero-medial eyespots. Another type of ciliated sensory cell is located between cornal cells. These intercoronal cells form synapses directly with the adjacent coronal cells. On the basis of these ultrastructural observations, the radial ciliated cells of the apical disc and the intercoronal cells are classified as primary sensory cells with different motor pathways. The radial ciliated cells are associated with the various effector organs of the larva via the nervous system. The intercoronal cells may combine sensory and motor functions by synapsing directly with the larval locomotory organ.
利用光学显微镜、扫描电子显微镜和透射电子显微镜，对类细胞唇口目苔藓虫Bugula stolonifera幼虫的纤毛感觉器官和效应器器官的超微结构进行了研究。幼虫体表由纤毛区域镶嵌而成，每个区域在组织结构和功能上都各具特色。最广泛的纤毛区域由触手冠的运动纤毛组成，这些纤毛共同构成了幼虫的主要运动器官，并覆盖了大部分幼虫体表。触手冠基部由环绕幼虫赤道的神经环支配。在反口极，一个由顶端盘上的放射状细胞带产生的不动的较短纤毛的圆形区域。放射状纤毛细胞与成对反口神经索下方的神经形成化学突触，这些神经索延伸至幼虫前侧中部赤道处的神经丛，位于梨形器官下方。梨形器官是沿着幼虫前中线排列的纤毛和腺区的复合体。它由从反口到口的顺序依次为：上腺区、摆动羽、下腺区和纤毛裂。摆动羽因其长度和摆动模式与周围的纤毛不同。它由四束约64μm长的纤毛组成，这些纤毛有节奏地同步摆动进入纤毛裂。每束纤毛都来自单个细胞，该细胞还具有粗壮微绒毛的顶端凹陷。腺区和摆动羽由各种先前未描述的纤毛细胞、纵向肌上皮细胞和一对前内侧眼点界定。另一种类型的纤毛感觉细胞位于触手冠细胞之间。这些触手冠间细胞直接与相邻的触手冠细胞形成突触。基于这些超微结构观察，顶端盘的放射状纤毛细胞和触手冠间细胞被归类为具有不同运动途径的初级感觉细胞。放射状纤毛细胞通过神经系统与幼虫的各种效应器器官相连。触手冠间细胞可能通过直接与幼虫运动器官形成突触来结合感觉和运动功能。
