Lectin histochemical studies on the olfactory gland and two types of gland in vomeronasal organ of the brown bear

In-depth histological, lectin-histochemical, immunohistochemical and ultrastructural description of the olfactory rosettes and olfactory bulbs of turbot (Scophthalmus maximus)

Chemical communication through olfaction is crucial for fish behaviours, mediating in socio-sexual behaviours as reproduction. Turbot, a flatfish with significant aquaculture production, possesses a well-developed olfactory system from early developmental stages. After metamorphosis, flatfish acquire their characteristic bilateral asymmetry with an ocular side facing the open water column, housing the dorsal olfactory rosette, and a blind side in contact with the sea bottom where the ventral rosette is located. This study aimed to address the existing gap in specific histological, ultrastructural, lectin-histochemical and immunohistochemical studies of the turbot olfactory rosettes and olfactory bulbs. We examined microdissected olfactory organs of adult turbots and premetamorphic larvae by using routine histological staining techniques, and a wide array of lectins and primary antibodies against G-proteins and calcium-binding proteins. We observed no discernible structural variations in the olfactory epithelium between rosettes, except for the dorsal rosette being larger in size compared to the ventral rosette. Additionally, the use of transmission electron microscopy significantly improved the characterization of the adult olfactory epithelium, exhibiting high cell density, small cell size, and a wide diversity of cell types. Moreover, specific immunopositivity in sensory and non-sensory cells provided us of essential information regarding their olfactory roles. The results obtained significantly enriched the scarce morphological and neurochemical information available on the turbot olfactory system, revealing a highly complex olfactory epithelium with distinct features compared to other teleost species, especially with regard to olfactory cell distribution and immunolabelling patterns.

The vomeronasal system of the wolf (Canis lupus signatus): The singularities of a wild canid

Wolves, akin to their fellow canids, extensively employ chemical signals for various aspects of communication, including territory maintenance, reproductive synchronisation and social hierarchy signalling. Pheromone-mediated chemical communication operates unconsciously among individuals, serving as an innate sensory modality that regulates both their physiology and behaviour. Despite its crucial role in the life of the wolf, there is a lacuna in comprehensive research on the neuroanatomical and physiological underpinnings of chemical communication within this species. This study investigates the vomeronasal system (VNS) of the Iberian wolf, simultaneously probing potential alterations brought about by dog domestication. Our findings demonstrate the presence of a fully functional VNS, vital for pheromone-mediated communication, in the Iberian wolf. While macroscopic similarities between the VNS of the wolf and the domestic dog are discernible, notable microscopic differences emerge. These distinctions include the presence of neuronal clusters associated with the sensory epithelium of the vomeronasal organ (VNO) and a heightened degree of differentiation of the accessory olfactory bulb (AOB). Immunohistochemical analyses reveal the expression of the two primary families of vomeronasal receptors (V1R and V2R) within the VNO. However, only the V1R family is expressed in the AOB. These findings not only yield profound insights into the VNS of the wolf but also hint at how domestication might have altered neural configurations that underpin species-specific behaviours. This understanding holds implications for the development of innovative strategies, such as the application of semiochemicals for wolf population management, aligning with contemporary conservation goals.

Immunohistological study of the unexplored vomeronasal organ of an endangered mammal, the dama gazelle (Nanger dama)

Dama gazelle is a threatened and rarely studied species found primarily in northern Africa. Human pressure has depleted the dama gazelle population from tens of thousands to a few hundred individuals. Since 1970, a founder population consisting of the last 17 surviving individuals in Western Sahara has been maintained in captivity, reproducing naturally. In preparation for the future implementation of assisted reproductive technology, certain aspects of dama gazelle reproductive biology have been established. However, the role played by semiochemical-mediated communications in the sexual behavior of dama gazelle remains unknown due partially to a lack of a neuroanatomical or morphofunctional characterization of the dama gazelle vomeronasal organ (VNO), which is the sensory organ responsible for pheromone processing. The present study characterized the dama gazelle VNO, which appears fully equipped to perform neurosensory functions, contributing to current understanding of interspecies VNO variability among ruminants. By employing histological, lectin-histochemical, and immunohistochemical techniques, we conducted a detailed morphofunctional evaluation of the dama gazelle VNO along its entire longitudinal axis. Our findings of significant structural and neurochemical transformation along the entire VNO suggest that future studies of the VNO should take a similar approach. The present study contributes to current understanding of dama gazelle VNO, providing a basis for future studies of semiochemical-mediated communications and reproductive management in this species. RESEARCH HIGHLIGHTS: This exhaustive immunohistological study of the vomeronasal organ (VNO) of the dama gazelle provides the first evidence of notable differences in the expression of neuronal markers along the rostrocaudal axis of the VNO. This provides a morphological basis for the implementation of pheromones in captive populations of dama gazelle.

Unique nasal septal island in dromedary camels may play a role in pain perception: microscopic studies

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The septal island in dromedaries is a distinctive anatomical structure.

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It has a curiously rostral location and innervated by the trigeminal nerve.

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It has an unusual ultrastructure and may be specialized for nociception.

The septal organs are islands or patches of sensory epithelium, located in the ventral parts of the nasal septum and innervated by the olfactory nerve. The septal island in dromedaries (Camelus dromedarius) was unusually located in the rostro-dorsal part of the nasal septum, where the ethmoidal branch of the trigeminal nerve provides innervation to the island mucosa. Therefore, the objectives of this study were to reveal the microscopic and ultrastructure of this island and to explain the probable functions. Twelve septal islands from 12 healthy male camels were used. Unlike the olfactory epithelium, which has a pseudostratified structure, the island neuroepithelium had a true neural lamination. Furthermore, in electron micrographs, the receptor, bipolar, and basal cells were connected with an orderly, organized network of cell–cell communication, which had some spine synapses. This network substituted the absence of supporting cells, maintained the shape of the tissue, and held the cells together. Moreover, the receptor cells were not similar to any of the different types of olfactory sensory neurons. Instead, they possessed the apical domain that might be specialized for the detection of chemical stimuli. Interestingly, a resident population of immune cells, namely mast cells and macrophages, was observed. The probable functions were discussed based on the cellular context and architecture. The nasal septal island in dromedaries may have a role in pain perception. The receptor cells most probably work as nociceptive cells that interact with the resident immune cells to coordinate pain signaling with immune response.

Comparative histological studies on properties of polysaccharides secreted by vomeronasal glands of eight Laurasiatheria species

Most mammalian species have a vomeronasal organ that detects specific chemical substances, such as pheromones. Mucous fluid covering the vomeronasal sensory epithelium is secreted by vomeronasal glands, and the properties of these fluids have been suggested to be involved in chemical detection. Histological studies using periodic acid-Schiff (PAS) and Alcian blue pH 2.5 (AB) stains, which respectively detect natural and acidic polysaccharides, have suggested variations in the nature of the vomeronasal glands among species. Here, we investigated the responsivity of the vomeronasal glands to PAS and AB stains in eight Laurasiatheria species. All species studied herein possessed vomeronasal glands that stained positive for PAS, like other many reported species. The vomeronasal glands of dogs and minks - like rodents, were AB-negative, whereas those of cows, goats, sika deer, musk shrews and two bat species were positive. Considering the present findings and previous reports, the vomeronasal glands in most of Laurasiatheria species appear to be fundamentally abundant in acidic polysaccharides, whereas those in carnivores essentially contains neutral polysaccharides.