Greenwald Lewis, Cook Clayton B, Ward Peter D
Department of Zoology, The Ohio State University, Columbus, Ohio 43210.
Department of Geology, University of California, Davis, California 95616.
J Morphol. 1982 Apr;172(1):5-22. doi: 10.1002/jmor.1051720103.
The siphuncle of the chambered nautilus (Nautilus macromphalus) is composed of a layer of columnar epithelial cells resting on a vascularized connective tissue base. The siphuncular epithelium taken from chambers that have not yet begun to be emptied of cameral liquid has a dense apical brush border. The great number of apical cell junctions (zonula adherens) compared to the number of nuclei suggests extensive interdigitation of these cells. The perinuclear cytoplasm of these preemptying cells is rich in rough endoplasmic reticulum. The siphuncular epithelium of both emptying and "old" siphuncle (which has already completed emptying its chamber) both show little rough endoplasmic reticulum but do contain extensive systems of mitochondria-lined infoldings of the basolateral plasma membranes. Active transport of NaCl into the extracellular space of this tubular system probably entrains the water transport involved in the chamber-emptying process. Both emptying and old siphuncular epithelium also show large basal infoldings (canaliculi) continuous with the hemocoel, which appear to be filled with hemocyanin. The apical cell junctions of emptying and old siphuncular epithelium contain septate desmosomes that may help to prevent back-flow of cameral liquid into the chambers.
鹦鹉螺（大脐鹦鹉螺）的体管由一层柱状上皮细胞组成，这些细胞位于血管化的结缔组织基部。取自尚未开始排空腔内液体的腔室的体管上皮具有密集的顶端刷状缘。与细胞核数量相比，大量的顶端细胞连接（黏着小带）表明这些细胞有广泛的相互交错。这些先占细胞的核周细胞质富含粗面内质网。正在排空的体管和“旧”体管（已经完成腔室排空）的体管上皮都几乎没有粗面内质网，但确实含有广泛的线粒体排列的基底外侧质膜内褶系统。氯化钠主动运输到这个管状系统的细胞外空间可能带动了腔室排空过程中涉及的水运输。正在排空的体管上皮和旧体管上皮还显示出与血腔连续的大的基底内褶（小管），这些内褶似乎充满了血蓝蛋白。正在排空的体管上皮和旧体管上皮的顶端细胞连接含有分隔桥粒，这可能有助于防止腔内液体回流到腔室中。
