Pablo Sanchez-Quinteiro

The organization of the olfactory systems remains poorly understood in mustelids, particularly in lutrines adapted to semiaquatic environments. This study provides the first detailed anatomical, histological, lectin-histochemical, and immunohistochemical characterization of the main (MOB) and accessory (AOB) olfactory bulbs of the Asian small-clawed otter ( Aonyx cinereus ). Serial transverse and sagittal sections were examined using Nissl and Tolivia staining, a panel of lectins, and neuronal and olfactory immunohistochemical markers. Macroscopically, the olfactory bulbs were prominent and elongated, although no distinct AOB could be identified. Histologically, the MOB displayed a well-developed laminar organization, abundant mitral and tufted cells, and a clearly defined lateral olfactory tract. By contrast, the AOB was small, located dorsocaudally within the olfactory peduncle, and lacked the canonical lamination observed in many other mammals. Its identification was supported by the selective binding of Ulex europaeus agglutinin and strong Gαi2 immunoreactivity in glomerular-like structures, whereas Gαo labeling was weak. LEA and STA labeled the superficial layers of both bulbs, while VVA and SBA recognized only scattered MOB glomeruli. Neuronal markers, including NCAM, NSE, NeuN, PGP 9.5, and β-tubulin III, confirmed the neuronal nature of the AOB, while calretinin strongly labeled its glomerular structures and projection neurons. These findings reveal a marked contrast between a highly developed MOB and a small, poorly laminated but neurochemically differentiated AOB. This organization indicates that the vomeronasal pathway is retained in A. cinereus, although in a structurally reduced form, and provides a comparative basis for investigating chemosensory evolution in semiaquatic carnivorans.

The olfactory system plays a crucial role in mediating fish behaviour, including reproduction. Senegalese sole (Solea senegalensis) is an important aquaculture flatfish species in Europe, in which reproductive dysfunction in captive males has been linked to potential alterations in chemical communication. Despite the expanded repertoire of olfactory receptor genes described for this species, detailed information on the cellular organization of its olfactory organs remains limited. This study provides a comprehensive histological, immunohistochemical, lectin-histochemical, and ultrastructural characterization of the olfactory rosettes of S. senegalensis across multiple life stages, including premetamorphic larvae, fry, juveniles and adults. Although the olfactory organs undergo substantial structural changes following metamorphosis, differentiated and functionally active olfactory sensory neurons (OSNs) are already present in premetamorphic larvae. Subsequently, two epithelial regions were distinguished along the olfactory lamellae: a sensory epithelium containing abundant OSNs and supporting cells, and a nonsensory epithelium dominated by goblet and other secretory cells. Ciliated and microvillous OSNs were distinguished from 60 dph onward based on morphological and ultrastructural features and supported by immunoreactivity with CR, CB, Gγ8 and PGP. Crypt cells showed immunolabelling with S100, NSE and CYK8. Furthermore, lectin histochemistry revealed ontogenetic changes in epithelial glycoconjugates, with early diffuse binding patterns evolving into stratified and region-specific distributions. Overall, these results demonstrate the structural and functional complexity of the olfactory epithelium in S. senegalensis, significantly enriching the limited available morphological and neurochemical information on the species.

The olfactory system plays a crucial role in mediating fish behavior, including reproduction. Senegalese sole (Solea senegalensis) is an important aquaculture flatfish species in Europe in which reproductive dysfunction in captive males has been linked to potential alterations in chemical communication. Despite the expanded repertoire of olfactory receptor genes described for this species, detailed information on the cellular organization of its olfactory organs remains limited. This study provides a comprehensive histological, immunohistochemical, lectin-histochemical, and ultrastructural characterization of the olfactory rosettes of S. senegalensis across multiple life stages, including premetamorphic larvae, fry, juveniles and adults. Although the olfactory organs undergo substantial structural changes following metamorphosis, differentiated and functionally active olfactory sensory neurons (OSNs) are already present in premetamorphic larvae. Subsequently, two epithelial regions were distinguished along the olfactory lamellae: a sensory epithelium containing abundant OSNs and supporting cells, and a nonsensory epithelium dominated by goblet and other secretory cells. Ciliated and microvillous OSNs were distinguished from 60 dph onward based on morphological and ultrastructural features and confirmed through immunoreactivity with CR, CB, Gγ8 and PGP. Crypt cells showed immunolabelling with S100, NSE and CYK8. Furthermore, lectin histochemistry revealed ontogenetic changes in epithelial glycoconjugates, with early diffuse binding patterns evolving into stratified and region-specific distributions. Overall, these results demonstrate the structural and functional complexity of the olfactory epithelium in S. senegalensis, significantly enriching the limited available morphological and neurochemical information on the species.

Shin T, et al. J Vet Sci. 2026 Jan;27:e13. https://doi.org/10.4142/jvs.25244

Pheromones are defined as substances released by an individual that have a specific influence on physiology, behaviour or development with another individual of the same species. Currently, the term pheromone is used in various disciplines, from psychology to electrophysiology, or to describe various chemosensory stimuli. The present literature review describes the main pheromone receptors and sources in rabbits, including the vomeronasal organ and the olfactory bulb; the main pheromone-producing glands are also described, such as the chin, anal, Harderian, mammary and the brown inguinal, as well as the urine as the major source for pheromonal communication. This review also provides a comprehensive examination of the role of pheromones in rabbit behaviour, integrating perspectives from physiology, behaviour and practical applications in rabbit farming. It delves into the mechanisms of pheromone action by discussing the main receptors and production sites, categorising pheromones in an orderly manner according to their functional roles in rabbits. Additionally, the review synthesises current research on pheromone influence, while highlighting both ecological implications and welfare improvements. By addressing these topics with scientific depth and practical relevance, this work offers an insightful understanding of rabbit pheromones and their diverse roles.

The vomeronasal system (VNS) is critical for detecting pheromonal cues that modulate sociosexual behaviors. Despite its central role in chemical communication, our understanding of its anatomical and functional variability across mammals remains incomplete. This study provides the first detailed characterization of the VNS in the Iberian mole ( Talpa occidentalis ), a fossorial species endemic to the Iberian Peninsula. We performed a morphofunctional and neurochemical analysis of the vomeronasal organ (VNO) and the accessory olfactory bulb (AOB) using histology, immunohistochemistry, and lectin histochemistry. The VNO in T. occidentalis exhibited an unusual circular lumen lined by a uniform sensory epithelium, lacking the dual epithelial organization seen in most species. The vomeronasal cartilage was limited in extent and did not form the typical J-shaped structure. Importantly, no evidence of a vomeronasal pump was found, suggesting alternative mechanisms for semiochemical entry, likely facilitated by the organ’s anatomical position and continuous receptor distribution. Immunohistochemical analysis revealed strong expression of Gαi2 and Gϒ8 in sensory neurons, with weaker Gα0 expression, suggesting predominance of V1R-type signal transduction. The AOB, though small, exhibited clear lamination and specific marker localization (Gαi2, OMP, CR, MAP2), indicating robust functional organization. Lectin binding revealed specific glycosylation patterns in the glomerular layer, with STL and LEA marking synaptic regions. These findings uncover unprecedented anatomical and molecular features in the VNS of T. occidentalis , positioning this species as a valuable model for studying vomeronasal diversity and evolution among Laurasiatherian mammals.

The vomeronasal system (VNS) plays a central role in mammalian chemical communication, mediating critical social and reproductive behaviors. In the wapiti ( Cervus canadensis ), a cervid species with complex social structures and pronounced chemical signaling during the rut, the VNS had not been previously characterized. This study provides the first comprehensive anatomical and neurochemical analysis of the VNS in wapiti using histological, lectin-histochemical, and immunohistochemical techniques. The vomeronasal organ (VNO) exhibited clear rostrocaudal differentiation, with distinct sensory and respiratory epithelia, a complex glandular distribution, and region-specific expression of neural markers. Lectin binding patterns confirmed functional compartmentalization along the epithelium, and immunoreactivity for markers such as OMP, PGP9.5, CR, and G-protein subunits (Gαi2, Gγ8, and Gα0) revealed detailed molecular organization. Notably, Gα0-positive neurons in the epithelium did not project to the accessory olfactory bulb (AOB), suggesting alternative targets, possibly within transitional zones. The AOB showed all canonical layers, including well-defined glomeruli and expression of markers such as calbindin, CR, GFAP, and LEA lectin. Novel findings include the presence of large white matter tracts and region-specific lectin distribution. Confocal double immunofluorescence and autofluorescence imaging were also employed, allowing high-resolution visualization of neuroepithelial architecture and glomerular domains. Altogether, our results demonstrate that the vomeronasal system in wapiti is highly developed and functionally specialized. These findings contribute to a better understanding of chemosensory communication in wild ungulates and provide a comparative framework for future studies in cervid behavior, reproduction, and conservation.

Background/Objectives: This study explores the ocular anatomy and glandular components of domestic dogs compared to their ancestor, the wolf, with the aim of identifying evolutionary changes due to domestication and their implications for ocular pathologies. Methods: Utilizing histological and histochemical techniques, including hematoxylin–eosin, Periodic Acid–Schiff, Alcian Blue, and lectins, this research conducts a detailed analysis of the canine and wolf ocular systems, focusing on the eyelids, tarsal glands, and conjunctival tissues. Results: There are marked histological differences between the two species, particularly in the thickness and secretion levels of the conjunctival epithelia and the structure of the tarsal glands. Dogs exhibit a thicker epithelium with greater Periodic Acid–Schiff and Alcian Blue positive secretion, suggesting enhanced ocular protection and lubrication adapted to domestic environments. Conversely, wolves display more concentrated glandular secretions and a predominance of acidic mucopolysaccharides, aligning with their adaptation to natural habitats. Conclusions: Although this study is constrained by the limited number of samples, the use of mixed dog breeds, and the focus on the Iberian wolf, it nonetheless suggests histological and evolutionary differences between domestic dogs and wolves, particularly in structures related to ocular surface protection and lubrication. These differences likely reflect adaptive responses to domestication in dogs and environmental demands in wolves. Importantly, the findings emphasize the clinical and translational potential of using dogs as comparative models for human ocular surface disorders, given their anatomical proximity to humans.

Inflammation of the vomeronasal organ (VNO) was evaluated in the context of experimental autoimmune encephalomyelitis (EAE). The VNO was sampled in mice with myelin oligodendrocyte glycoprotein-induced EAE, and processed for paraffin embedding. The sections were immunohistochemically evaluated for various markers, including ionized calcium binding adaptor molecule 1 (Iba1), myeloperoxidase (MPO), and olfactory marker protein (OMP). Inflammatory cell infiltration was detected in the connective tissues. Both Iba1-positive macrophages and MPO-positive neutrophils infiltrated the VNO of EAE, with increased secretion of mucus into the lumen. The intensity of the OMP-positive immunoreaction was decreased in the vomeronasal sensory epithelium of EAE-induced mice. We postulate that the inflammatory response of the VNO in EAE is associated with dysfunction of the accessory olfactory system.