Antifreeze glycoprotein, discovered by
Arthur L. DeVries in the 1960's, is also an example of
convergent evolution. Scientists have determined that the
arctic cod and the antarctic
icefish (notothenioids) have nearly identical AFGP. This originally led them to believe the fish might have a
common ancestor, but further analysis revealed that the
gene expression in the two was completely different.
In the icefish, the gene expression for AFGP is nearly identical with its gene expression for the digestive enzyme trypsinogen; the arctic cod's AFGP gene does not resemble its gene for trypsinogen, nor does it resemble the icefish's gene for AFGP. The only reasonable conclusion then is that they developed AFGP independently - or convergently.
The antarctic icefish are notable for more than AFGP; they are also the only vertebrates lacking red blood cells.