Ontogeny of the olfacto-retinalis projection in coho salmon (Oncorhynchus kisutch)

Filling of nucleus olfacto-retinalis neurons by cobaltous lysine injections into one eye of coho salmon of different ages revealed that the terminal nerve projection to the retina is established when the fish leave their freshwater environment. At this time salmons go through a metamorphosis termed "smoltification." FMRF-amide-like immunoreactive neurons in the nucleus olfacto-retinalis already exist in pre-smolts before the retino-petal projection is established. Thus, for the first time in any vertebrate, a projection of the terminal nerve is shown to develop during an advanced ontogenetic state.