West J A, Sivak J G, Doughty M J
School of Optometry, University of Waterloo, Canada.
Exp Eye Res. 1995 Jan;60(1):19-35. doi: 10.1016/s0014-4835(05)80080-6.
The similarity between the cephalopod lens and the teleost (vertebrate) lens can be considered an optical example of convergent evolution. However, the embryology and ultrastructure of the cephalopod lens appear to be different from that of vertebrates, and perhaps unique to the animal kingdom. Using light and scanning electron microscopy, the morphogenesis of the squid (Loligo opalescens) lens is characterized. Results indicate that the posterior lens primordium appears first during development and is derived from cellular processes which extend from a middle group, group 2, of lentigenic (ectodermal) cells. The processes extend from the basal aspect of the lentigenic cells, project down into the optic vesicle during early stages of development, and fuse to form the posterior lens primordium. During later stages, the processes extend from surrounding lentigenic cells and are applied to the stalk of the lens, where they form bud-shaped protrusions. Once applied to the lens, the processes form lens elements that later fuse into plate-like elements evident in later-staged embryo and adult lenses. The anterior lens primordium is derived from an anterior group, group 1, of lentigenic cells, during later stages of development. Lentigenic processes extend from these lentigenic cells and are laid down in a circumferential fashion to form the anterior lens cap. As in the posterior lens, evidence indicates that the anterior lens elements fuse to form plate-like elements. The ultrastructure and morphogenesis of the cephalopod lens is discussed and contrasted with other strategies of lens development.
头足类动物的晶状体与硬骨鱼（脊椎动物）的晶状体之间的相似性可被视为趋同进化的一个光学实例。然而，头足类动物晶状体的胚胎学和超微结构似乎与脊椎动物不同，也许在动物界是独一无二的。利用光学显微镜和扫描电子显微镜对头足类动物（太平洋褶柔鱼）晶状体的形态发生进行了表征。结果表明，晶状体后原基在发育过程中首先出现，它源自从中间一组（第2组）成晶状体（外胚层）细胞延伸出的细胞突起。这些突起从成晶状体细胞的基部延伸，在发育早期向下伸入视泡，并融合形成晶状体后原基。在后期，这些突起从周围的成晶状体细胞延伸出来，并附着在晶状体的柄上，在那里形成芽状突起。一旦附着在晶状体上，这些突起就形成晶状体元件，这些元件后来融合成在晚期胚胎和成年晶状体中可见的板状元件。晶状体前原基在发育后期源自前一组（第1组）成晶状体细胞。成晶状体突起从这些成晶状体细胞延伸出来，并以圆周方式排列形成晶状体前帽。与晶状体后原基的情况一样，有证据表明晶状体前元件融合形成板状元件。本文对头足类动物晶状体的超微结构和形态发生进行了讨论，并与晶状体发育的其他方式进行了对比。
