Simple (dorsal light reflex) and complex (predator-prey interactions)
visually mediated behaviors were used concurrently with morphological
examination to assess restoration of visual function following optic nerve
crush in bluegill (Lepomis macrochirus) × pumpkinseed
(Lepomis gibbosus) hybrid sunfish. Regenerating optic nerve axons
projected into the stratum opticum-stratum fibrosum et griseum
superficiale by week 2, the stratum griseum centrale by week
4, and stratum album centrale by week 6. Initial projections into
the laminae were diffuse and less stratified compared to controls. By week
12, the projection pattern of regenerating nerve fibers closely resembled
the innervation of normal tecta. Visual improvements were correlated with
increasing projections into the tectum. The dorsal light reflex improved
from a 45° vertical deviation following nerve crush to 4.5° by
week 16. Initial predator-prey interactions were exclusively mediated by
the control eye. As regeneration progressed, there was a gradual expansion
of the visual field. The reaction distance and attack angles within the
visual field of the experimental eye were initially less than controls,
however, these differences disappeared by week 10. Improvements in visual
function were closely correlated with an increase of regenerating ganglion
cell axons into the optic tectum indicating sufficient synaptogenesis to
mediate both simple and complex visual behavior.