The evolutionary trajectories of the individual amygdala nuclei in the common shrew, guinea pig, rabbit, fox and pig: A consequence of embryological fate and mosaic-like evolution

Functional Role of the Incisive Duct in Neonatal Dogs

INTRODUCTION

The detection of chemical signals by the vomeronasal organ (VNO) is critical for mammals from an early age, influencing behaviors such as suckling and recognition of the mother. Located at the base of the nasal cavity, the VNO features a duct covered with a sensory epithelium. A critical aspect of VNO functionality is the efficient access of stimuli from the nasal and oral cavities to the receptors. In adult dogs, it has been demonstrated how the vomeronasal duct (VD) communicates to the environment through the incisive duct (ID). In newborn puppies, the existence of functional communication between the ID and the VD has not been confirmed to date, raising doubts about the potential physiological obliteration of the ID. Determining this aspect is necessary to evaluate the role played by chemocommunication in the survival and socialization of puppies.

METHODS

This study employs serial histological staining to examine the presence and functionality of the ID in neonatal dogs. Additionally, a histochemical study was conducted using periodic acid-Schiff and Alcian Blue staining, along with labeling with six lectins to characterize the expression of glycoconjugates in the incisive papilla and in the area between the ID and the VD.

RESULTS

The histological study has confirmed both the existence of functional communication between both ducts in perinatal puppies and the dual functional communication of the ID with the oral and nasal cavities. Lectin labeling has allowed for the characterization of the glycoconjugate expression profile in the papilla and ID, showing significant differences between lectins.

CONCLUSION

The ID is associated with a sophisticated cartilaginous complex that prevents its collapse, as well as erectile tissue that acts as a cushion, facilitating its action under pressure induced by sampling behaviors such as tonguing. This investigation demonstrates the communicative capabilities of the VNO during the perinatal stage in dogs.

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.

Human Amygdala Volumetric Patterns Convergently Evolved in Cooperatively Breeding and Domesticated Species

The amygdala is a hub in brain networks that supports social life and fear processing. Compared with other apes, humans have a relatively larger lateral nucleus of the amygdala, which is consistent with both the self-domestication and the cooperative breeding hypotheses of human evolution. Here, we take a comparative approach to the evolutionary origin of the relatively larger lateral amygdala nucleus in humans. We carry out phylogenetic analysis on a sample of 17 mammalian species for which we acquired single amygdala nuclei volumetric data. Our results indicate that there has been convergent evolution toward larger lateral amygdala nuclei in both domesticated and cooperatively breeding mammals. These results suggest that changes in processing fearful stimuli to reduce fear-induced aggression, which are necessary for domesticated and cooperatively breeding species alike, tap into the same neurobiological proximate mechanism. However, humans show changes not only in processing fearful stimuli but also in proactive prosociality. Since cooperative breeding, but not domestication, is also associated with increased proactive prosociality, a prominent role of the former during human evolution is more parsimonious, whereas self-domestication may have been involved as an additional stepping stone.

The brain of the silver fox (Vulpes vulpes): a neuroanatomical reference of cell-stained histological and MRI images

Although the silver fox (Vulpes vulpes) has been largely overlooked by neuroscientists, it has the potential to serve as a powerful model for the investigation of brain-behavior relationships. The silver fox is a melanistic variant of the red fox. Within this species, the long-running Russian farm-fox experiment has resulted in different strains bred to show divergent behavior. Strains bred for tameness, aggression, or without selection on behavior present an excellent opportunity to investigate neuroanatomical changes underlying behavioral characteristics. Here, we present a histological and MRI neuroanatomical reference of a fox from the conventional strain, which is bred without behavioral selection. This can provide an anatomical basis for future studies of the brains of foxes from this particular experiment, as well as contribute to an understanding of fox brains in general. In addition, this can serve as a resource for comparative neuroscience and investigations into neuroanatomical variation among the family Canidae, the order Carnivora, and mammals more broadly.