Life on Earth may have developed the ability to form embryos before the first animals appeared. A single-celled organism that lives buried in mud in shallow waters bears a striking resemblance to animal embryos in the process of reproduction, according to a group of scientists led by biochemist Marin Olivetta of the University of Geneva. The pattern of division is similar to the process of embryonic cell division.
The organism in question is the ichthyospore microbe Chromosphaera perkinsii, and since it has existed for more than a billion years, long before the first animals, its existence suggests that life evolved a program for eggs before egg cells appeared.
“Although C. perkinsii is a single-celled species, this behavior suggests that multicellular coordination and differentiation processes were already present in this species long before the appearance of the first animals,” biochemist Omaya Dudin from the Swiss Federal Institute of Technology explains. Soil.”
Multicellular animal organisms begin their lives in the same way. The two zygotes fuse and fuse, triggering the process of cell division and growth. The first stages of cell division are called fission; At this stage rapid division occurs without growth; This process is known as palintomy. The end product of this process is a cluster of cells with a hollow center, similar to a raspberry fruit. This is called blastula.
This process is seen as a means of reproduction in animals and single-celled organisms. The organism divides into several daughter cells, which separate and become independent. And in fact, scientists have drawn parallels between these two processes before. A paper published earlier this year suggested that ichthyospores could be an excellent model for understanding the origins of animals.
This is because ichthyospores are a class of single-celled organisms that diverged from the lineage that gave rise to animals a billion years ago. They are not animals, but they are closely related to them, and any similarities between animals and ichthyospores may have been inherited from a common ancestor before the lineages diverged. Earlier this year, a group of scientists, including Olivetti, published a paper describing palintomic reproduction in C. perkinsii, similar to animal mitosis.
Dudin and colleagues examined C. perkinsii, one of the few non-parasitic ichthyospores, compared to several other members of the class to see whether there were more similarities between palintomic reproduction and fission in animal embryos.
They found that after palinotomy, C. perkinsii formed a blastula-like cluster of cells. And there are at least two different types of cells in this colony. The mass of cells then remains in this blastula-like colony for most of its life cycle, before the cells eventually disperse and go about their own business.
It is surprisingly similar to the development of an animal embryo. This suggests that development may be related between animals and ichthyospores, and that genetic programming of embryonic development occurs even before embryos appear.
But nature is also very good at copying things that work. Sometimes traits or processes arise independently in very different organisms; this process is known as convergent evolution. Colony development and aggregation of C. perkinsii appear unusual; this was not observed in other ichthyospores.
In fact, except for some scattered partial observations, no animal embryos or other animal relatives such as C. perkinsii develop. This suggests that convergent evolution may be the answer; but we also cannot rule out a common ancestor.
In any case, many interesting things await us. On the one hand, C. perkinsii may open new opportunities for understanding the evolutionary origins of all animals. On the other hand, it suggests that the genetic toolkit available for early life is much more versatile than we thought.
“Future studies will be important to clarify how spatial cell differentiation occurs in C. perkinsii,” the researchers write in their paper. “However, our study shows that C. perkinsii represents a transitional form between temporal and spatial cell differentiation, providing insight into the evolutionary mechanisms that led to the emergence of multicellularity in animals.” The results of the research were published at: Nature.
Source: Port Altele
