Polymorphism is a general concept in biology where more than one version of a trait is present in a population.
Trichomycterus davisi, for example, is an extreme case where the polymorphism was present within a single chimeric individual.
[1] It has also been studied in alfalfa,[2] shrews,[3] Brazilian rodents,[4] and an enormous variety of other animals and plants.
[6] Another process resulting in differing chromosomal counts is polyploidy.
This results in cells which contain multiple copies of complete chromosome sets.