Caceci Thomas, Hrubec Terry C
Department of Biomedical Sciences, Virginia/Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.
Department of Pathobiology, Virginia/Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.
J Morphol. 1990 Jun;204(3):265-280. doi: 10.1002/jmor.1052040305.
A light and electron microscopic (TEM and SEM) study of the gut of the black mollie (Poecilia spp.) shows that the gut is a relatively undifferentiated muscular tube lined with a simple columnar epithelium. The mucosa and underlying lamina propria are formed into folds. The apices of the folds form obtuse angles at the cranial end and more acute ones caudally. The mucosal epithelium is a simple columnar sheet with PAS-positive goblet cells interspersed throughout. The enterocytes are covered apically with uniform microvilli in most of the tract, and the plasma membrane deeply infolded basally. Mitochondria are located in the basal folds. A continuous basal lamina separates the epithelial mucosa from the underlying lamina propria. Enterocytes have a PAS-positive Golgi apparatus in the supranuclear region. The enterocytes of the cranial and middle thirds of the gut are morphologically indistinguishable, but those in the caudal third display shorter and sparser microvilli. There is no evidence of pinocytotic activity in the enterocytes of the cranial two thirds of the gut tube, but some apical pinocytotic vesicles are seen in the cells in the caudal third. The tunica muscularis consists of two layers of smooth muscle, inner circular and outer longitudinal. We observe lateral separation of enterocytes from each other deep to the junctional complexes in the caudal and midgut regions. The gut of the mollie lacks some of the specialized cell types commonly found in other fishes. It cannot create an acidic gastric environment; overall control of digestive activity, osmolarity, and ionic balance presumably rest in the structural relationships between epithelial cells and between the epithelium and its supporting tissues. Regional specialization of cells and of the gut as a whole may confer digestive function equivalent to that found in more complicated systems.
对黑摩利鱼（食蚊鱼属）肠道进行的光学显微镜和电子显微镜（透射电镜和扫描电镜）研究表明，肠道是一个相对未分化的肌性管，内衬单层柱状上皮。黏膜和其下方的固有层形成褶皱。褶皱顶端在头端形成钝角，在尾端形成更锐角。黏膜上皮是单层柱状上皮，其间散布着PAS阳性杯状细胞。在肠道大部分区域，肠细胞顶端覆盖着均匀的微绒毛，质膜在基部深陷折叠。线粒体位于基部褶皱中。连续的基膜将上皮黏膜与下方的固有层分隔开。肠细胞在核上区有一个PAS阳性的高尔基体。肠道头三分之一和中三分之一处的肠细胞在形态上无法区分，但尾三分之一处的肠细胞微绒毛更短且更稀疏。在肠道头三分之二的肠细胞中没有胞饮活性的证据，但在尾三分之一处的细胞中可见一些顶端胞饮小泡。肌层由两层平滑肌组成，内层为环行肌，外层为纵行肌。我们观察到在尾肠和中肠区域，肠细胞在连接复合体深部彼此侧向分离。摩利鱼的肠道缺乏其他鱼类中常见的一些特化细胞类型。它无法营造酸性胃环境；消化活动、渗透压和离子平衡的总体控制大概取决于上皮细胞之间以及上皮与其支持组织之间的结构关系。细胞和整个肠道的区域特化可能赋予其与更复杂系统相当的消化功能。
