Hamilton K A, Linberg K A, Case J F
C.V. Whitney Laboratory, University of Florida, St. Augustine, Florida.
Department of Biological Sciences and Marine Science Institute, University of California, Santa Barbara, California.
J Morphol. 1985 Sep;185(3):349-366. doi: 10.1002/jmor.1051850307.
In the kelp crab, Pugettia producta, flat plate setae cover all but the ventral surfaces of the walking leg dactyls. Dendrites enter the setal shaft located inside the plate superstructure, and extend to a region of the setal tip that contains a system of minute pores resembling the pore systems found in chemosensory sensilla of insects. Presumably, much of the chemosensitivity of the dactyls in the kelp crab is mediated by the plate setae. In the interior of the dactyl, supporting cells and the neurons innervating plate setae, other types of setae, and other presumptive sensilla form scolopidia. Large scolopidia, containing as many as 12 dendrites, appear to innervate some of the plate setae and also large ventral rodlike setae that might be chemosensory. Two of the dendrites of large scolopidia usually have more densely packed microtubules, longer ciliary axonemes, slightly larger rootlets, and dark A fibers with arms, characteristics indicative of mechanosensory function. Some dactyl setae, therefore, could be both mechanosensory and chemosensory. Small scolopidia containing two or three dendrites that exhibit mechanosensory characteristics appear to innervate small, rodlike setae, which presumably are strictly mechanosensory. The two types of structures located on the epicuticular cap, elliptical structures resembling campaniform sensilla and small cones in pits resembling CAP organs, appear to be dually innervated and presumably are mechanosensory, although other functions are possible. The internal positions of the scolopidia, together with the support afforded by an extracellular dendritic sheath, by the scolopale, and by desmosomelike and septate junctions, may serve to protect internal portions of setal dendrites, some of which appear to remain functional in nonmolting adults that have abraded setae.
在海带蟹（Pugettia producta）中，平板刚毛覆盖了步足指节除腹面之外的所有表面。树突进入位于平板上层结构内部的刚毛轴，并延伸至刚毛尖端的一个区域，该区域包含一个微小孔隙系统，类似于在昆虫化学感受感器中发现的孔隙系统。据推测，海带蟹指节的大部分化学敏感性是由平板刚毛介导的。在指节内部，支持细胞以及支配平板刚毛、其他类型刚毛和其他假定感器的神经元形成了弦音器。大型弦音器含有多达12个树突，似乎支配着一些平板刚毛以及一些可能具有化学感受功能的大型腹侧棒状刚毛。大型弦音器的两个树突通常具有更密集排列的微管、更长的纤毛轴丝、稍大的小根以及带有臂的深色A纤维，这些特征表明其具有机械感受功能。因此，一些指节刚毛可能兼具机械感受和化学感受功能。含有两到三个表现出机械感受特征树突的小型弦音器似乎支配着小型棒状刚毛，这些刚毛大概严格来说是机械感受性的。位于表皮帽上的两种结构，类似于钟形感器的椭圆形结构和类似于CAP器官的凹坑中的小锥体，似乎接受双重神经支配，大概是机械感受性的，尽管也可能有其他功能。弦音器的内部位置，连同细胞外树突鞘、弦音管以及桥粒样和分隔连接提供的支撑，可能有助于保护刚毛树突的内部部分，其中一些在刚毛磨损的非蜕皮成体中似乎仍保持功能。
