Thanks to the marine worm Platynereis dumerilii, an animal whose genes have evolved very slowly, a team of scientists have shown that while haemoglobin appeared independently in several species, it in fact descends from a unmarried gene transmitted to all by their final common ancestor.
The findings of the study by scientists from CNRS, Universite de Paris and Sorbonne Universite, in organization with others at the University of Saint Petersburg and the University of Rio de Janeiro, were published in the publication BMC Evolutionary Biology.
Having red blood isn’t unusual to humans or mammals. This colour comes from haemoglobin, a complex protein specialized in transporting the oxygen found in the circulatory system of vertebrates, but also in annelids (a worm circle of relatives whose most famed members are earthworms), molluscs (particularly pond snails) and crustaceans (such as daphnia or ‘water fleas’). It was once thought that for haemoglobin to have appeared in such diverse species, it should have been ‘invented’ several times all the way through evolution. But recent research has shown that every one of these haemoglobins born ‘independently’ in fact derive from a unmarried ancestral gene.
Researchers from the Institut Jacques Monod (CNRS/Universite de Paris), the Laboratoire Matiere et Systemes Complexes (CNRS/Universite de Paris), the Station Biologique de Roscoff (CNRS/Sorbonne Universite), the Universities of Saint Petersburg (Russia) and Rio de Janeiro (Brazil), conducted this research on Platynereis dumerilii, a small marine worm with red blood.
It is thought of as to be an animal that evolved slowly, because its genetic characteristics are near to those of the marine ancestor of most animals, Urbilateria(1). Studying these worms by comparing them with other species with red blood has helped in tracing back to the origins of haemoglobins.
The research focused on the broad circle of relatives to which haemoglobins belong: globins, proteins present in nearly all living beings that ‘store’ gases like oxygen and nitric oxide. But globins generally act within the cells because they don’t circulate in the blood like haemoglobin.
This work shows that in all species with red blood, it’s the same gene that makes a globin called ‘cytoglobin’ that independently evolved to turn into a haemoglobin-encoding gene. This new circulating molecule made oxygen transport more efficient in their ancestors, who became larger and more active.
Scientists now need to change scale and continue this work by studying when and how the different specialized cells of bilaterian vascular systems emerged.
(1)Urbilateria is the final common ancestor of bilaterians, i.e. animals with bilateral (left-right) symmetry and complex organs, aside from species with simpler association such as sponges and jellyfish.
(This story has been published from a wire agency feed without modifications to the text.)
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