![]() "There is a lot of evidence that the sponge epithelial cells and the muscle cells of all the other animals are going back to a common contractile cellular predecessor." In future, scientists hope to test this hypothesis using genome and gene expression-related data. ![]() "But surely there must have been evolutionary predecessor systems, that have been unknown until now." The sponge epithelial cells are now moving to the forefront in the evolutionary biologists' continuing research in this field. According to current scientific knowledge, muscle cells seem to have surfaced from nowhere," Nickel says. "The early evolution of muscles has not been fully understood so far. These findings offer new approaches to understanding the evolutionary development of musculature. But now, the Jena scientists have been able to identify the true initiator of the contractions. Until recently, spindle-shaped cells in the tissue of sponges as well as epithelial cells were thought to be possible candidates. Ultimately, the Jena scientists believe they have also settled a hundred-year-old debate about the cause of cellular contractions. Nickel's team was able to show that the inner and outer surfaces - and therefore the epithelial cells, so-called pinacozytes - cause the strong body contractions of the sponges. "Although the 3-D volumetric analysis is widely known and used in the technical sciences, it has rarely been used in zoology - in spite of its enormous information potential." "A key feature of our approach is the use of 3-D data for measuring the volume and surface of our sponges," says Nickel. Using this technique, the Jena scientists, in co-operation with the Helmholtz-Zentrum Gesthacht at the Deutsches Elektronen Synchrotron Hamburg, were able to compare and visualize the 3-D structure of contracted and expanded sponges. Strange Sex When you never move, reproduction can be a tad tricky. As sessile organisms, once they have established themselves, they anchor to whatever substrate they have landed on. ![]() However, the fact that the ciliated larvae of sponges swim faster than the other phyla caught our. The amount of data collected by the authors is impressive and the outcomes of this dataset are also noteworthy. In their paper, the researchers described how they generated three-dimensional (3-D) images, with the help of synchrotron radiation-based X-ray microtomography. Sessile Once they have found a suitable home, sponges plant themselves in place and do not move. trophic larvae of sessile organisms (especially sponges) swim faster than those of non-sessile animals (polychaetes and echinoderms). In a new study published in the Journal of Experimental Biology, the evolutionary biologists are offering new answers to this question. The scientists from the Institute of Systematic Zoology and Evolutionary Biology are especially interested in the question of which evolutionary forerunners did muscle cells derive from. Michael Nickel of Friedrich Schiller University Jena (Germany) is looking into movement without muscles. A group of scientists headed by associate professor Dr.
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