School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Centre for Zoo and Wild Animal Health, Copenhagen Zoo, Frederiksberg, Denmark.
J Comp Neurol. 2021 Jan;529(1):8-27. doi: 10.1002/cne.25047. Epub 2020 Oct 14.
Employing cyto-, myelo-, and chemoarchitectural staining techniques, we analyzed the structure of the hippocampal formation in the banded mongoose and domestic ferret, species belonging to the two carnivoran superfamilies, which have had independent evolutionary trajectories for the past 55 million years. Our observations indicate that, despite the time since sharing a last common ancestor, these species show extensive similarities. The four major portions of the hippocampal formation (cornu Ammonis, dentate gyrus, subicular complex, and entorhinal cortex) were readily observed, contained the same internal subdivisions, and maintained the topological relationships of these subdivisions that could be considered typically mammalian. In addition, adult hippocampal neurogenesis was observed in both species, occurring at a rate similar to that observed in other mammals. Despite the overall similarities, several differences to each other, and to other mammalian species, were observed. We could not find evidence for the presence of the CA2 and CA4 fields of the cornu Ammonis region. In the banded mongoose the dentate gyrus appears to be comprised of up to seven lamina, through the sublamination of the molecular and granule cell layers, which is not observed in the domestic ferret. In addition, numerous subtle variations in chemoarchitecture between the two species were observed. These differences may contribute to an overall variation in the functionality of the hippocampal formation between the species, and in comparison to other mammalian species. These similarities and variations are important to understanding to what extent phylogenetic affinities and constraints affect potential adaptive evolutionary plasticity of the hippocampal formation.
采用细胞、骨髓和化学构筑染色技术，我们分析了带纹獴和雪貂这两个肉食动物超科物种的海马结构。这两个物种在过去的 5500 万年中各自独立进化。我们的观察表明，尽管它们已经有共同祖先 5500 万年了，但这些物种仍表现出广泛的相似性。海马结构的四个主要部分（角状回、齿状回、下托复合体和内嗅皮质）很容易观察到，包含相同的内部细分，并且保持了这些细分的拓扑关系，可以被认为是典型的哺乳动物。此外，两种物种都观察到成年海马神经发生，其发生速度与其他哺乳动物相似。尽管存在总体相似性，但也观察到了一些与其他哺乳动物物种的差异。我们没有发现角状回区域 CA2 和 CA4 字段存在的证据。在带纹獴中，齿状回似乎由多达七个层组成，通过分子和颗粒细胞层的亚分层，而在雪貂中则没有观察到这种情况。此外，在两种物种之间还观察到了许多化学构筑的细微差异。这些差异可能导致了物种之间海马结构功能的总体差异，以及与其他哺乳动物物种的比较。这些相似性和差异对于理解种系发生亲缘关系和约束在多大程度上影响海马结构的潜在适应性进化可塑性非常重要。
