The transparency allows us to study the regeneration of neurons in the intact animal. See this link to watch Joe talk about this work. We have collaborated with the Schaffer/Nishimura lab to do similar imaging in living mice.
A damaged neuron can be induced to regrow by application of the drug cyclic AMP. Top shows the Mauthner cell in the brain of the fish. The axon of the cell extends into spinal cord. After damage, the axon dones not regrow on its own (middle panel). But, by squirting cyclic AMP on it, it can regrow as in the bottom panel.
The transparency of the fish allows us to watch the regrowth in the intact animal. Images in the movie were taken every hour for 36 hours as the severed axon (left) grew toward the tail (right).
Imaging of fluorescently labeled axons (green) and myelin in living mice done in collaboration with the Schaffer/Nishimura lab.