Primate blood discovered in a 30-million-year-old fossil

This fossilized tick in amber contains mammalian blood.
This fossilized tick in amber contains mammalian blood. © JOURNAL OF MEDICAL ENTOMOLOGY / GEORGE POINAR

An American researcher discovered inside the body of a tick trapped in amber, blood cells belonging to a mammal, and more particularly, a primate.

The story begins as the scenario of Jurassic Park : an American researcher has discovered, trapped in amber, an arthropod filled with blood. Except that the fossilized specimen is not a mosquito but a tick (so an arachnid) and that the discovered blood is not that of a dinosaur but of a mammal. George Poinar, a researcher in the Department of Integrative Biology at Oregon State University in the United States, presented in an article published in the Journal of Medical Entomology on March 20, 2017 , which seem to be the first Blood cells of fossilized discovered mammals.

Incredibly well-preserved mammalian blood cells

After a meticulous study of the sample found in a mine in the Dominican Republic, the researcher was able to see that the tick trap, corresponding to the genus Ambylomma,  contained several mammalian blood cells (photo below).

The latter are easily recognizable thanks to their biconcave disk shape and the absence of nuclei. Their observation allowed the American scientist to discover a pathogen named Piroplasmida  within some of these cells. This organism is a eukaryotic parasite (possessing a nucleus) known to be transmitted to mammals by a tick bite.

Credit: Journal of Medical Entomology / George Poinar
Credit: Journal of Medical Entomology / George Poinar

The tick and its host lived tens of millions of years ago

Since the 1940s, scientists know that the size of blood cells can vary from one species to another. For example, ungulates, bats and rodents range in diameter from 2.7 to 6.6 micrometers, while the blood cells of lagomorphs (rabbit, etc.), canids and primates have a diameter Between 6.9 and 7.3 micrometers. The size of the discovered cells corresponds to the second category. No fossil of canidae or lagomorphs has been found on the island of Hispaniola (home to the Dominican Republic and Haiti).

However, remains of primates have already been discovered. In analyzing the composition of amber, the researcher has deduced that the tick, like its host, had lived 20 to 30 million years ago, that is to say in the middle of the Tertiary era . For the scientist, the mammal in question was probably a primate, “ a kind of Platyrhinian (also called „New World Monkeys“)  who lived in a forest on the island . But unlike dinosaurs, these animals still occupy our planet: the analogy with Jurassic Park stops there.