Developmental shifts in functional morphology of the retina in Atlantic tarpon, Megalops atlanticus (Elopomorpha: Teleostei) between four ecologically distinct life-history stages
Developmental shifts in functional morphology of the retina in Atlantic tarpon, Megalops atlanticus (Elopomorpha: Teleostei) between four ecologically distinct life-history stages
复制标题
大西洋大海鲢（Elopomorpha：Teleostei）视网膜功能形态在四个生态不同的生活史阶段之间的发育变化
作者：
Scott M. Taylor;E. Loew;M. Grace
摘要大西洋罗非鱼是一种大型食鱼性鱼类，支持墨西哥湾、加勒比海和佛罗里达大西洋沿岸重要的经济休闲渔业。大西洋巨鱼在形态上经历了发育变化，幼体在公海中孵化(长度不到1厘米)，幼体进入缺氧浑浊的红树林沼泽(长度约10厘米)，然后作为成体进入沿海水域(长度超过100厘米)。本研究分别用光学显微镜、透射电子显微镜、抗视蛋白免疫荧光和显微分光光度法研究了四个不同的生活史阶段--变态前期幼虫、安置期、幼虫和成虫的感光器分布、视蛋白分布和吸光度特性。本研究的目的是1)确定大西洋鳗视网膜在发育过程中的变化程度，2)将这些视网膜变化与不同发育阶段之间的生态变化联系起来。这里提供的新数据表明，大西洋黄鼠的视网膜在发育过程中视杆和视锥的分布和吸收特性发生了实质性的变化，并且这些变化与栖息地和行为密切相关。我们表明，大西洋分枝杆菌在幼虫阶段的视网膜以杆状为主(这在硬骨鱼幼虫中是罕见的)，随着成熟，暗视系统变得更好地发育，增加了大量的绒毛膜和高密度的小的、捆绑的和堆叠的杆状细胞。我们还表明，视锥和视杆的光谱敏感度发生了变化，光谱不同的视锥类别的多样性增加，包括随着鱼类成熟成鱼，增加了紫外线视锥。
Abstract The Atlantic tarpon, Megalops atlanticus, is a large piscivorous fish that supports economically important recreational fisheries in the Gulf of Mexico, Caribbean, and Florida Atlantic coast. Megalops atlanticus undergoes ontogenetic shifts in morphology, hatching in the open ocean as larvae (less than 1 cm in length), moving into hypoxic turbid mangrove marshes as juveniles (around 10 cm in length), and then moving into coastal oceanic waters as adults (over 100 cm in length). In this study, photoreceptor distributions, opsin distributions, and photoreceptor absorbance characteristics were studied with light microscopy, transmission electron microscopy, antiopsin immunofluorescence, and microspectrophotometry, respectively, at four ecologically distinct life-history stages—premetamorphic larva, settlement stage, juvenile, and adult. The purposes of this study were 1) to determine the extent to which the retina of M. atlanticus changes over the course of development and 2) to relate these retinal changes with ecological shifts between developmental stages. The new data presented here indicate that the M. atlanticus retina changes substantially in rod and cone distributions and absorbance characteristics over the course of development and that these changes correlate closely with those in habitat and behavior. We show that M. atlanticus has a rod-dominated retina at the larval stage (which is unusual for teleost larvae) and that the scotopic visual system becomes far better developed with maturity, adding a substantial tapetum and high densities of small, bundled, and stacked rod cells. We also show that there are shifts in cone and rod spectral sensitivities and an increase in the diversity of spectrally distinct cone classes, including the addition of ultraviolet cones as fish mature into adults.