Department of Anatomy, Animal Production and Clinical Veterinary Sciences, Faculty of Veterinary, University of Santiago de Compostela, Lugo, Spain.
J Anat. 2020 Nov;237(5):890-906. doi: 10.1111/joa.13254. Epub 2020 Jun 25.
The vomeronasal system (VNS) has been extensively studied within specific animal families, such as Rodentia. However, the study of the VNS in other families, such as Canidae, has long been neglected. Among canids, the vomeronasal organ (VNO) has only been studied in detail in the dog, and no studies have examined the morphofunctional or immunohistochemical characteristics of the VNS in wild canids, which is surprising, given the well-known importance of chemical senses for the dog and fox and the likelihood that the VNS plays roles in the socio-reproductive physiology and behaviours of these species. In addition, characterising the fox VNS could contribute to a better understanding of the domestication process that occurred in the dog, as the fox would represent the first wild canid to be studied in depth. Therefore, the aim of this study was to analyze the morphological and immunohistochemical characteristics of the fox VNO. Tissue dissection and microdissection techniques were employed, followed by general and specific histological staining techniques, including with immunohistochemical and lectin-histochemical labelling strategies, using antibodies against olfactory marker protein (OMP), growth-associated protein 43 (GAP-43), calbindin (CB), calretinin (CR), α-tubulin, Gαo, and Gαi2 proteins, to highlight the specific features of the VNO in the fox. This study found significant differences in the VNS between the fox and the dog, particularly concerning the expression of Gαi2 and Gαo proteins, which were associated with the expression of the type 1 vomeronasal receptors (V1R) and type 2 vomeronasal receptors (V2R), respectively, in the vomeronasal epithelium. Both are immunopositive in foxes, as opposed to the dog, which only expresses Gαi2. This finding suggests that the fox possesses a well-developed VNO and supports the hypothesis that a profound transformation in the VNS is associated with domestication in the canid family. Furthermore, the unique features identified in the fox VNO confirm the necessity of studying the VNS system in different species to better comprehend specific phylogenetic aspects of the VNS.
犁鼻器系统（VNS）在特定的动物科中，如啮齿动物，已经得到了广泛的研究。然而，在其他科中，如犬科，对 VNS 的研究长期以来一直被忽视。在犬科中，只有狗的犁鼻器官（VNO）被详细研究过，而且没有研究检查过野生犬科动物 VNS 的形态功能或免疫组织化学特征，这令人惊讶，因为众所周知，化学感觉对狗和狐狸很重要，而且 VNS 可能在这些物种的社会生殖生理学和行为中发挥作用。此外，描述狐狸的 VNS 可以帮助更好地理解狗发生的驯化过程，因为狐狸将成为第一个被深入研究的野生犬科动物。因此，本研究的目的是分析狐狸 VNO 的形态和免疫组织化学特征。采用组织解剖和微解剖技术，结合一般和特殊的组织学染色技术，包括使用针对嗅觉标记蛋白（OMP）、生长相关蛋白 43（GAP-43）、钙结合蛋白（CB）、钙调蛋白（CR）、α-微管蛋白、Gαo 和 Gαi2 蛋白的免疫组织化学和凝集素组织化学标记策略，突出了狐狸 VNO 的特异性特征。本研究发现狐狸和狗之间的 VNS 存在显著差异，特别是在 Gαi2 和 Gαo 蛋白的表达上，这与犁鼻上皮中 1 型犁鼻受体（V1R）和 2 型犁鼻受体（V2R）的表达有关，分别。在狐狸中，这两种蛋白都是免疫阳性的，而狗只表达 Gαi2。这一发现表明，狐狸拥有一个发达的 VNO，并支持这样一种假设，即 VNS 的深刻转变与犬科的驯化有关。此外，在狐狸 VNO 中发现的独特特征证实了在不同物种中研究 VNS 系统的必要性，以更好地理解 VNS 的特定系统发育方面。
