The January tetra (Hemigrammus hyanuary Durbin) exhibits two eye color phenotypes. These have a silver iris, which is characteristic of the species, and a green color variant. Segregation patterns observed in the progenies from 12 different crosses support an hypothesis for the monogenic inheritance of iris coloration in this species.
Frankel, Jack, "Monogenic control of iris coloration in the January tetra (Hemigrammus hyanuary Characidae)" (1999). Department of Biology Faculty Publications. 137.