Comparative Studies of Brain Development

Acomys cahirinus (the "spiny mouse")

newborn rat and acomys pup

Acomys (a mouse indigenous to the Sinai desert) is in the same evolutionary group as the lab rat or mouse (Muridae). The more common lab animals are born in a very immature state (they are "altricial", see the rat pup at left above) while Acomys is born with its ears and eyes open and easily moves about within hours of birth. It is rare when two closely related animals have such divergent developments. In a series of studies (listed below) we compared patterns of brain growth between these species. Since every evolutionary change occurs as a result of a modification in development, the work addressed both issues.

Monodelphis domestica (gray, short-tailed opposum)

Monodelphis domestica

Monodelphis (a Brazilian opossum), like most marsupials, gives birth after a very short gestation (13 days) to very immature pups (the neural tube closes in the telencephalic regions about 24 hours before birth). Unlike other marsupials Monodelphis has no pouch: pups simply find a nipple on the mother's ventrum and firmly attach-- litters hang like grapes off of the the mother. As a result, they allow easy examination of very early stages of brain development. We took advantage of these features in the studies listed below.

Monodelphis pups



Fish are the most abundant and diverse of the vertebrates. In two sets of studies we examined several aspects of the development of their olfactory systems, including the ability of their olfactory nerves to regenerate after being cut and the early expression of the genes used to code olfactory receptors.