Development of the olfactory system in a wallaby (Macropus eugenii)

Area of Science:

• Neuroscience
• Developmental Biology
• Comparative Anatomy

Background:

• The ability of newborn marsupials to locate the nipple is crucial for survival.
• The olfactory system's role in guiding neonates to the nipple is well-established in eutherians but less understood in marsupials.

Purpose of the Study:

• To investigate the developmental maturity of olfactory pathways in newborn tammar wallabies (Macropus eugenii).
• To test the hypothesis that the olfactory system is mature at birth and aids in nipple-finding behavior.

Main Methods:

• Carbocyanine dye tracing, hematoxylin and eosin staining, and immunohistochemistry for GAP-43 were employed.
• Tritiated thymidine autoradiography was used to assess neuronal generation in the piriform cortex.

Main Results:

• Olfactory pathways, including the vomeronasal organ and olfactory bulb, are immature at birth (postnatal day 0).
• While some early olfactory projections exist, they are not sufficiently developed to guide nipple-finding.
• Piriform cortex neurons are generated postnatally, precluding their involvement in early guidance.

Conclusions:

• The hypothesis that olfactory projections guide newborn tammar wallabies to the nipple is rejected.
• The trigeminal nerve pathways, being more mature at birth, likely play a significant role in nipple-finding behavior.