Fritzsch B
Faculty of Biology, University of Bielefeld, FRG.
Brain Behav Evol. 1988;31(6):325-48. doi: 10.1159/000116599.
The inner-ear and lateral-line afferents were studied in members of almost all urodele families and in two primitive representatives of anurans and gymnophionans by means of transganglionically transported horseradish peroxidase. The lateral-line projection patterns are, when present, identical in all urodeles and gymnophionans. This is in agreement with the presence of ampullary organs in all urodeles and gymnophionans which possess a lateral-line neuromast system. In contrast, even the most primitive anurans lack both ampullary organs and the dorsal projection of afferents from these organs. In urodeles the inner-ear afferents are found to enter the rhombencephalon via the octaval nerve and bifurcate in the neuropil lateral to the nucleus magnocellularis into a short ascending and a longer descending subpial fascicle. Fibers of the ascending fascicle reach the tip of the lateral recess and terminate in the eminentia granularis. Collaterals are confined to the ipsilateral lobulus lateralis and end presumably as mossy fibers. The descending fascicle ends at the obex level with only a few fibers reaching the second spinal segment. Besides extensive fiber supply to the cells of the ipsilateral ventral-zone column, collaterals are found to reach the reticular formation, nucleus cerebelli, nucleus fasciculus solitarius, intermediate nucleus and several motor nuclei. Differences in the octaval projection among urodele families are limited to variation in its size relative to that of the lateral-line projection. Only species that develop without free-living larvae differ markedly with respect to the absence of lateral-line projections and, presumably, the lateral-line nuclei of the alar plate that exists in larvae. Almost all urodeles that possess a lateral-line system as larvae retain a complete lateral-line system, including neuromasts and ampullary organs, after metamorphosis. Only Salamandra and Chioglossa lose most of their lateral-line afferents and presumably all lateral-line organs around metamorphosis. The octavolateralis projections in urodeles are found to be strikingly similar to those in lampreys, sharks, sturgeons, and, especially, gymnophionans. This points to a great conservatism of this pattern, at least among anamniotic vertebrates. However, even primitive anurans such as Ascaphus differ markedly from these patterns in that they show no ampullary organs or dorsal lateral-line projection but a dorsal projection of the inner ear. Outgroup comparison with other anamniotic vertebrates indicates that the pattern in anurans is derived from the more generalized lateral-line and inner-ear projection pattern as represented in many urodeles and gymno
通过跨神经节运输辣根过氧化物酶，对几乎所有有尾目家族的成员以及无尾目和蚓螈目的两个原始代表的内耳和侧线传入神经进行了研究。侧线投射模式（如果存在）在所有有尾目和蚓螈目中都是相同的。这与所有有尾目和蚓螈目都存在壶腹器官且拥有侧线神经丘系统是一致的。相比之下，即使是最原始的无尾目也既没有壶腹器官，也没有来自这些器官的传入神经的背侧投射。在有尾目中，内耳传入神经通过八叉神经进入后脑，并在大细胞外侧的神经毡中分叉，形成一个短的上升和一个较长的下降软膜下束。上升束的纤维到达外侧隐窝的尖端，并终止于颗粒隆起。侧支局限于同侧外侧小叶，可能以苔藓纤维的形式终止。下降束在闩平面结束，只有少数纤维到达第二脊髓节段。除了向同侧腹侧区柱的细胞提供广泛的纤维供应外，还发现侧支到达网状结构、小脑核、孤束核、中间核和几个运动核。有尾目家族之间八叉神经投射的差异仅限于其与侧线投射大小的相对变化。只有那些没有自由生活幼虫而发育的物种，在没有侧线投射以及可能没有幼虫中存在的翼板侧线核方面有明显差异。几乎所有幼虫期拥有侧线系统的有尾目在变态后都保留了完整的侧线系统，包括神经丘和壶腹器官。只有蝾螈属和盲螈属在变态前后失去了大部分侧线传入神经，可能还失去了所有侧线器官。有尾目的八侧线投射被发现与七鳃鳗、鲨鱼、鲟鱼，尤其是蚓螈目的八侧线投射惊人地相似。这表明这种模式具有很大的保守性，至少在无羊膜脊椎动物中是这样。然而，即使是像尾蟾这样的原始无尾目，在模式上也与这些有明显不同，因为它们没有壶腹器官或背侧侧线投射，而是有内耳的背侧投射。与其他无羊膜脊椎动物的类群比较表明，无尾目的模式是从许多有尾目和蚓螈目所代表的更普遍的侧线和内耳投射模式衍生而来的。
