The Cambrian Explosion is widely regarded as one of the most relevant episodes in the history of life on Earth, when the vast majority of animal phyla first appear in the fossil record. However, the causes of its origin have been the subject of debate for decades, and the question of what was the trigger for the single cell microorganisms to assemble and organize into multicellular organisms has remained unanswered until now.
Within a longstanding research collaboration between the Institute for Bioengineering of Catalonia and Bielefeld University together with the Friedrich-Miescher-Institute in Basel and the Marine Biological Laboratory at Woods Hole (Massachusetts), Xavier Fernàndez-Busquets (Barcelona) and Dario Anselmetti (Bielefeld) and their colleagues published online in the journal Molecular Biology and Evolution their biophysical single molecule results on the effect of calcium on the interactions of cell adhesion molecules from marine sponges. These simply organized organisms do not have specialized muscle or nerve cells and nevertheless survived the last 500 million years almost unchanged and are considered a link between the single-cell dominated Precambrian and later multicellular organisms.
The researchers succeeded to show that the massive and sudden surge in the calcium concentration of the Cambrian seawater -- that is believed to be the result of volcanically active midocean ridges -- not only initiated the buildup of calcified shells, but was also mandatory for the aggregation and stabilisation of multicellular sponge structures. This allows, on the other hand, to formulate a novel theory where the geologically induced increase of marine calcium might be the key for understanding the Cambrian Explosion of Life.
This paper constitutes the first research work where single molecule force spectroscopy studies have provided meaningful answers to such a deep evolutionary biology question as the origin of multicellular animals, and might represent a milestone for both disciplines and an example of how multidisciplinarity and collaboration are essential components of excellent contemporary science.
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