Pettigrew J D, Maseko B C, Manger P R
Queensland Brain Institute, University of Queensland 4072, Upland Road, Brisbane, QLD 4072, Australia.
Neuroscience. 2008 Apr 22;153(1):226-31. doi: 10.1016/j.neuroscience.2008.02.019. Epub 2008 Feb 21.
The current study was designed to reveal the retinotectal pathway in the brain of the echolocating megabat Rousettus aegyptiacus. The retinotectal pathway of other species of megabats shows the primate-like pattern of decussation in the retina; however, it has been reported that the echolocating Rousettus did not share this feature. To test this prior result we injected fluorescent dextran tract tracers into the right (fluororuby) and left (fluoroemerald) superior colliculi of three adult Rousettus. After a 2-week survival period the animals were killed, fixed via transcardial perfusion, and the retinas whole mounted and examined under fluorescent excitation to reveal the pattern of retrograde transport. Red and green labeled retinotectal ganglion cells were found in side-by-side patches on either side of a vertical decussation line in the temporal retina of all six retinas. The Rousettus examined thus exhibited the same pattern of retinal decussation as reported previously for other megabats and primates, but unlike that seen in other mammals. The current result indicates that the prior study appears to have suffered technical problems leading to an incorrect conclusion. The results of our study indicate that, as may be expected, all megabats share the derived retinotectal pathway once thought to be the exclusive domain of primates. The current study provides additional support for the diphyletic origin of the Chiroptera and aligns the megabats phylogenetically as a sister group to primates.
本研究旨在揭示回声定位的大蝙蝠埃及果蝠大脑中的视网膜顶盖通路。其他种类大蝙蝠的视网膜顶盖通路呈现出类似灵长类动物的视网膜交叉模式；然而，据报道，回声定位的埃及果蝠并不具备这一特征。为了验证这一先前的结果，我们向三只成年埃及果蝠的右侧（氟鲁比）和左侧（氟翠玉）上丘注射了荧光葡聚糖束示踪剂。在2周的存活期后，处死动物，通过经心灌注固定，将视网膜整体固定并在荧光激发下检查，以揭示逆行运输模式。在所有六个视网膜颞侧视网膜垂直交叉线两侧的并排区域中发现了红色和绿色标记的视网膜顶盖神经节细胞。因此，所检查的埃及果蝠表现出与先前报道的其他大蝙蝠和灵长类动物相同的视网膜交叉模式，但与其他哺乳动物不同。目前的结果表明，先前的研究似乎存在技术问题，导致得出了错误的结论。我们的研究结果表明，正如预期的那样，所有大蝙蝠都共享曾经被认为是灵长类动物独有的衍生视网膜顶盖通路。本研究为翼手目的双系起源提供了额外支持，并在系统发育上将大蝙蝠定位为灵长类动物的姐妹群。
