For deer mice, Peromyscus maniculatus , much of their lives are spent in an orgy. These North American rodents are extraordinarily promiscuous. Also, do not feel bad at all. In 2012, a team of researchers from the University of California, Berkeley, presented the results of a study where it was clear that, over time, this behavior has ended up strengthening their immune system. In contrast, their monogamous cousins of the Peromyscus polionotus species are more prone to certain infectious diseases.
Apart from this, these animals are so similar that they could even reproduce with each other. And yet another group of scientists, coordinated by the evolutionary biologist Hopi Hoekstra, of Harvard University, has found that the differences in their sexuality go far beyond their habits: deer mice, which in their encounters change their mate every few minutes , they present a gene that makes their sperm faster and more vigorous and move more efficiently through the female’s reproductive tract.
Hoekstra and his colleagues found that their sperm have small, expanded sections in the midpiece, a region below the head and neck. These contain a large number of mitochondria , cellular organelles that function as power plants and that promote the movements of the sperm.
To try to determine what is the genetic basis that explains such dissimilarity between the two mice, the researchers bred hybrid rodents and studied the length of the aforementioned expanded sections in their progeny, as well as the speed at which their sperm moved. In this way, they found that a protein that encodes the PrKar1a gene was abundantly produced in them – this also plays a role in male fertility in humans -, which suggests that it is involved in the function of these sections. In fact, they observed that this protein was not found in equal amounts in deer mice and Peromyscus polionotus .
As these scientists explain on the bioRxiv portal, males raised from laboratory rodents with only one copy of the PrKar1a gene had shorter sections. For Hoekstra and his team, this suggests that the sperm of deer mice, which given their habits have to compete with that of other individuals, has altered the activity of this gene in this species, which, in turn, has caused a sperm that moves faster.
Experts warn that this study may shed some light on the still little known genetic mechanisms involved in sperm motility , that is, in their ability to move. This can decisively affect fertility, because if it is low the chances of them reaching the ovum are reduced.
Image: 6th Happiness via Wikimedia / CC
