Mammals and lice evolved together

July 4. () –

The first louse to take up residence on a mammalian host likely began as a parasite of birds, according to a new study published in the journal ‘Nature Ecology & Evolution’.

That host jump tens of millions of years ago kicked off the long association between mammals and lice, laying the foundation for their co-evolution and offering more opportunities for lice to spread to other mammals.

The study compares the genomes and family trees of lice and their mammalian hosts. The effort revealed that the two trees share many branches and parallel branching. Those branch points, where a group of mammals began to diverge into new forms, were often echoed in the genomes of the lice that parasitized those mammals, the researchers report. it’s a statement.

“In this paper, we use data from genome sequencing to demonstrate that a recently recognized important group of mammalian lice, including lice of humans, originated from the common ancestor of Afrotheria, a group of mammals with a primarily African distribution. including elephants, giraffes, and elephant shrews, among others,” explains Kevin P. Johnson, principal investigator and ornithologist at the Illinois Natural History Survey, who led the study along with Jorge Doña, a Marie Curie postdoctoral researcher at the University of Illinois Urbana-Champaign (United States) and the University of Granada–. These lice went on to colonize other major groups of mammals through the process of host switching.”

Lice are divided into two groups based on their eating habits. Chewing lice feed on the skin or secretions, while sucking lice pierce the skin to consume the blood of their hosts, Johnson explains. Both types feed on mammals, but sucking lice are exclusive to mammals.

Recent genomic studies revealed that sucking lice are closely related to two groups of chewing lice that also feed on mammals, and “each of the major groups within this newly identified lineage occurs in at least one member of Afrotheria”, the researchers wrote. Afrotheria is an ancient lineage of mammals that includes elephants, elephant shrews, hurricanes, golden moles, and mites, among others.

That research suggested that members of Afrotheria were the original mammalian hosts for lice. Johnson and Doña expanded the genomic sampling of mammalian lice to include more Afrotheria-associated lice and compared the evolutionary history of mammals and their lice. Specifically, they included lice from elephant shrews and hurricanes.

Their analysis indicated that elephant lice, hyraxes, and elephant shrews were the oldest of the group of chewing and sucking lice that fed on mammals.

“This shows that these mammalian lice began in this strange group of African mammals and changed to other mammals later.Johnson notes.

Host switching from birds to mammals was very rare, he says. The team found evidence that this happened only a few times: to Madagascar lemurs, South American rodents and some marsupials, for example.

But once lice learned to feed on mammals, they were able to jump more easily from one species of mammal to another, and probably had more opportunities to do so. And when certain groups of mammals became separated, say geographically, they diverged and so did their lice.according to the analysis.

Although more work needs to be done to trace the evolutionary history of lice and their hosts, Johnson notes that lice probably date back 90 to 100 million years and probably first parasitized dinosaurs or birds.

“And then when the dinosaurs went extinct about 65 million years ago and the birds and mammals really diversified, lice also began to jump to new hosts and to diversify“, Add.