Katagiri N, Terakita A, Shichida Y, Katagiri Y
Section of Basic Science, Tokyo Women's Medical University School of Nursing, Shizuoka, Japan [corrected].
J Comp Neurol. 2001 May 7;433(3):380-9. doi: 10.1002/cne.1146.
The stalk eye of Onchidium sp. (Gastropoda, Mollusca) is the principal photoreceptor in a multiple photoreceptive system that consists of the stalk and dorsal eyes, dermal photoreceptor cells, and photosensitive neurons. To examine the localization of photopigments, the stalk eyes were immunostained with specific antibodies to rhodopsin, retinochrome, and retinal-binding protein (RALBP), which had been generated against squid retinal proteins. The retina of the stalk eye was divided into villous, pigmented, somatic, and neural layers. It was comprised mainly of two types of visual and pigmented supportive cells. The type 1 visual (VC1) cell was characterized by well-developed microvilli on its apical protrusion and photic vesicles in the cytoplasm. The photic vesicles were specifically blackened by prolonged osmification. The type 2 visual (VC2) cell had less numerous, shorter microvilli on its concave apical surface and lacked photic vesicles. The anti-squid rhodopsin antiserum was localized specifically to the villous layer that corresponded to the VC1 microvilli. With the anti-retinochrome peptide antibody, the somatic layer showed specific but patchy, positive staining that corresponded to the cytoplasm of the VC1 cells. Because the photic vesicles are known to contain retinochrome, these results indicate that this retinochrome is localized in the VC1 cytoplasm. Anti-RALBP antibody stained the supranuclear cytoplasm to the distal cytoplasm of VC1 cells. This is the first demonstration of the localization of RALBP in the Gastropoda Onchidium stalk eye. In squid retina that were immunostained as positive controls, the anti-rhodopsin antibody stained rhabdomeric microvilli, the anti-retinochrome antibody stained the inner segment and the basal region of the outer segment, and the anti-RALBP antibody stained the outer and inner segments, respectively. These results suggest that the rhodopsin-retinochrome system that has been established in cephalopod eyes is present in the Onchidium stalk eye.
石磺科（腹足纲，软体动物）的柄眼是一个多重感光系统中的主要光感受器，该系统由柄眼和背眼、真皮感光细胞以及感光神经元组成。为了检测光色素的定位，用针对鱿鱼视网膜蛋白产生的视紫红质、视黄醛色素蛋白和视网膜结合蛋白（RALBP）的特异性抗体对柄眼进行免疫染色。柄眼的视网膜分为绒毛层、色素层、体细胞层和神经层。它主要由两种类型的视觉和色素支持细胞组成。1型视觉（VC1）细胞的特征是其顶端突起上有发育良好的微绒毛，细胞质中有光小泡。通过长时间的锇酸浸染，光小泡会被特异性地染黑。2型视觉（VC2）细胞在其凹陷的顶端表面有较少且较短的微绒毛，并且没有光小泡。抗鱿鱼视紫红质抗血清特异性地定位于与VC1微绒毛相对应的绒毛层。用抗视黄醛色素蛋白肽抗体检测时，体细胞层呈现出与VC1细胞的细胞质相对应的特异性但斑驳的阳性染色。因为已知光小泡中含有视黄醛色素蛋白，这些结果表明这种视黄醛色素蛋白定位于VC1细胞质中。抗RALBP抗体对VC1细胞的核上细胞质到远端细胞质进行了染色。这是首次证明RALBP在腹足纲石磺柄眼中的定位。在作为阳性对照进行免疫染色的鱿鱼视网膜中，抗视紫红质抗体对小网膜微绒毛进行了染色，抗视黄醛色素蛋白抗体对外部段的内段和基部区域进行了染色，抗RALBP抗体分别对外部段和内部段进行了染色。这些结果表明，在头足类眼睛中建立的视紫红质 - 视黄醛色素蛋白系统也存在于石磺柄眼中。
