Structure and diversity in mammalian accessory olfactory bulb

Area of Science:

• Neuroscience
• Comparative Anatomy
• Evolutionary Biology

Background:

• The accessory olfactory bulb (AOB) serves as the primary neural center for the vomeronasal sensory system.
• Understanding the AOB's structure and evolutionary history is crucial for deciphering its role in sensory processing.

Purpose of the Study:

• To provide an overview of the vomeronasal system and the discovery of the mammalian AOB.
• To review the evolutionary trajectory of the vomeronasal system across vertebrates, with a focus on reptiles.
• To discuss the structural and phylogenetic diversity of the AOB in mammals and its functional implications.

Main Methods:

• Comparative analysis of AOB structure and occurrence across diverse vertebrate taxa.
• Review of existing literature on vomeronasal system organization, evolution, and AOB development.
• Examination of species-specific variations in AOB size, shape, and morphology.

Main Results:

• The AOB is present in terrestrial tetrapods (amphibians, reptiles, mammals) but absent in fish and birds.
• Significant variation exists in AOB presence, size, and morphology across mammalian orders, with some species lacking it in adulthood.
• The AOB develops embryonically in many species but may regress later, indicating complex regulatory mechanisms.

Conclusions:

• The accessory olfactory bulb exhibits remarkable evolutionary diversity, reflecting adaptations to various ecological niches.
• Variations in AOB structure and presence suggest potential functions beyond traditional roles in sexual and reproductive behaviors.
• Further research into the vomeronasal system's receptor diversity and projection pathways is needed to explore novel functions.