Pushchin Igor I, Zyumchenko Nataliya E
1 Laboratory of Physiology A.V. Zhirmunsky Institute of Marine Biology of the Far Eastern Branch of the Russian Academy of Sciences Vladivostok, Russia.
2 Department of Cell Biology and Genetics School of Natural Sciences, Far Eastern Federal University Vladivostok, Russia.
J Integr Neurosci. 2015 Dec 1:1550028. doi: 10.1142/S0219635215500284.
The vertebrate visual system is determined by two main factors, a species' lifestyle and phylogenetic legacy. Studying the visual system in outgroup lineages may shed some light on the balance of these factors within a certain radiation. We studied the topography of retinal ganglion cells (RGCs) in the retina of the oriental fire-bellied toad Bombina orientalis. These toads belong to the ancient superfamily Discoglossoidea, a sister group to all extant Anura except for two small families. RGCs were retrogradely labeled with tetramethylrhodamine- dextran amine (TMR-DA) and examined in retinal wholemounts. RGCs occurred all over the retina except for the far periphery. Their total number was [Formula: see text] ([Formula: see text], [Formula: see text]). They comprised 73-77% of all cells in the ganglion cell layer. The spatial density of GCs increased gradually from the dorsal and ventral retinal periphery toward the equator to form a weak visual streak and a moderately pronounced area centralis. The minimum density was [Formula: see text], and the maximum, [Formula: see text]. The maximum density gradient was [Formula: see text]. The spatial resolution was minimum in the dorsal and ventral periphery ([Formula: see text] and [Formula: see text] cycles per degree in water and air, respectively). Intermediate values of spatial resolving power were found within the visual streak ([Formula: see text] and [Formula: see text] cycles per degree) and reached a peak in area centralis ([Formula: see text] and [Formula: see text] cycles per degree). This is sufficient for efficient prey location and capture. The relatively high RGC density and the presence of specialized retinal regions in oriental fire-bellied toads are consistent with their highly visual behavior. A brief review comparing the phylogeny and ecology of this with other anuran species suggests that the main factor shaping the RGC distribution in Anura is phylogenetic legacy; the environmental pressure results mainly in adjusting the maximum spatial density of RGCs (and hence the visual acuity) to meet the species' needs.
脊椎动物的视觉系统由两个主要因素决定，即物种的生活方式和系统发育遗产。研究外类群谱系中的视觉系统可能有助于揭示特定辐射范围内这些因素的平衡情况。我们研究了东方铃蟾（Bombina orientalis）视网膜中视网膜神经节细胞（RGCs）的拓扑结构。这些蟾蜍属于古老的盘舌蟾超科，是除两个小科之外所有现存无尾目动物的姐妹群。通过四甲基罗丹明-葡聚糖胺（TMR-DA）对RGCs进行逆行标记，并在视网膜整体标本中进行检查。除了最外周区域外，RGCs遍布整个视网膜。其总数为[公式：见正文]（[公式：见正文]，[公式：见正文]）。它们占神经节细胞层中所有细胞的73 - 77%。GCs的空间密度从视网膜背侧和腹侧外周向赤道逐渐增加，形成一条微弱的视觉条纹和一个中度明显的中央区。最小密度为[公式：见正文]，最大密度为[公式：见正文]。最大密度梯度为[公式：见正文]。空间分辨率在背侧和腹侧外周最小（在水中和空气中分别为每度[公式：见正文]和[公式：见正文]周/度）。在视觉条纹内发现空间分辨能力的中间值（每度[公式：见正文]和[公式：见正文]周/度），并在中央区达到峰值（每度[公式：见正文]和[公式：见正文]周/度）。这足以有效地定位和捕获猎物。东方铃蟾相对较高的RGC密度以及专门视网膜区域的存在与其高度视觉化行为一致。将其与其他无尾目物种的系统发育和生态进行比较的简要综述表明，塑造无尾目RGC分布的主要因素是系统发育遗产；环境压力主要导致调整RGCs的最大空间密度（从而调整视敏度）以满足物种需求。
