By Mark Brown, Wired UK

Feathered dinosaurs may have been the first animals bedeviled by lice. That’s the finding of Illinois ornithologist Kevin Johnson, after tracing the evolutionary line of the critters back millions of years.

Johnson and his team worked out a partial family tree of lice by comparing the DNA sequences of genes from 69 present-day louse lineages. Changes in the gene sequence give a reliable measure of how far apart these species have evolved. Because the alterations accumulate over millions of years, they can give a rough timeline of the evolution of organisms.

The lice family tree indicates that the blood-sucking parasites lived long before the dinosaurs were killed off, 65 million years ago. In the paper, published in the journal Biology Letters, Johnson says the humble louse could be as old as the early- to mid-Cretaceous period: 115 to 130 million years ago. They probably latched on to feathered theropod dinosaurs (like the fluffy Sinornithosaurus found in China, which lived around 125 million years ago), making our extinct lizard chums the first animals to be tormented by the itchy critters.

But the research has also shed new light on the theory that birds and mammals only started diversifying — to the owls, ducks and parrots of today — after the dinosaurs were wiped out. This hypothesis, supported by evidence that the only fossils resembling modern animals come from earlier than 65 million years ago, might be proven wrong by Johnson’s lice.

Because lice undergo intense specialization to match their hosts — evolving elongated bodies to bury themselves between the barbs of a bird’s feather or gaining grooves on their head to clasp onto a strand of gopher hair — they find it difficult to leap between different animals.

This means lice generally evolve in step with their hosts, and become impromptu markers to lay out the evolutionary history of the birds and mammals they infest. “Lice are like living fossils,” said colleague and Natural History Museum researcher Vincent Smith said in a press release. “The record of our past is written in these parasites.”

“Our analysis suggests that both bird and mammal lice began to diversify before the mass extinction of dinosaurs,” Johnson said in the release. Where there’s diversified bird and mammal lice, there’s probably diversified birds and mammals.

The ornithologist also speculates that perhaps today’s birds, thought to be descendants of feathered dinosaurs, maybe just “inherited their lice from dinosaurs.”

Image: Left: A fossilized louse that may have preyed on dinosaurs. Right: Modern louse. (Vincent S. Smith/University of Illinois)

Source: Wired.co.uk

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