Mutation speeds up sperm of zebra finches

In zebra finches, sperm velocity and morphology and hence reproductive success strongly depend on a specific mutation (an inversion) on one of the sex chromosomes, called Z. This was discovered by scientists of the Max Planck Institute for Ornithology in Seewiesen. Males always carry two copies of the Z chromosome, but those that possess two different versions of it, one regular and one inverted, benefit from an optimal sperm design. Even under the strongest selection, in which only the fastest