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Chromosphaera perkinsii is a single-celled organism that was identified in 2017 in marine sediments near Hawaii. Evidence suggests it has existed on Earth for over a billion years, predating the first animals. Researchers from the University of Geneva (UNIGE) discovered that this organism forms multicellular structures that remarkably resemble animal embryos. These findings imply that the genetic mechanisms needed for embryonic development were present long before animals evolved or that C. perkinsii developed similar mechanisms separately. Thus, nature may have had the genetic capabilities to “create eggs” well before it “invented chickens.” This research has been published in the journal Nature.
The earliest life forms on Earth were single-celled organisms, such as yeast and bacteria. Later on, multicellular organisms like animals emerged, developing from a single cell (the egg) into complex life forms. This embryonic development follows specific stages that show striking similarities across animal species, which may trace back to times long before animals even existed. However, the transition from single-celled to multicellular organisms remains poorly understood.
Omaya Dudin, recently appointed as an assistant professor in the Department of Biochemistry at UNIGE, and previously an SNSF Ambizione researcher at EPFL, has been studying Chromosphaera perkinsii, an ancient protist species. This organism diverged from the animal lineage over a billion years ago, providing important insights into the processes that might have led to the evolution of multicellularity.
While examining C. perkinsii, researchers found that these cells, after reaching full size, divide without further growth, forming multicellular colonies that echo the initial stages of animal embryonic development. Uniquely, these colonies can last for about a third of their lifespan and include at least two different types of cells, a surprising trait for a single-celled organism.
”Despite being unicellular, C. perkinsii illustrates that processes of multicellular coordination and differentiation were already in place in this species, well before the first animals emerged”, states Omaya Dudin, who led the study.
Even more remarkably, the manner in which these cells divide and the three-dimensional shapes they take closely resemble the early stages of animal embryonic development. In collaboration with Dr. John Burns from the Bigelow Laboratory for Ocean Sciences, researchers analyzed the gene activity in these colonies and found intriguing parallels to that found in animal embryos, indicating that the genetic frameworks for complex multicellular development existed over a billion years ago.
Marine Olivetta, a lab technician at UNIGE and the principal author of the study, comments: “It’s amazing that a species discovered so recently allows us to look back over a billion years.” The research suggests either embryonic development principles were in place prior to animals or that mechanisms for multicellular development evolved independently in C. perkinsii.
This discovery could provide new perspectives on a longstanding scientific debate surrounding fossils that are around 600 million years old, which resemble embryos, and could question some traditional ideas about the nature of multicellularity.
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