Evolution is not a one-way road towards complexity

There are still a lot of unanswered questions about mollusks, e.g. snails, slugs and mussels. The research group of Andreas Wanninger, Head of the Department of Integrative Zoology of the University of Vienna, took a detailed look at the development of cryptic worms. The larvae of the "wirenia argentea" hold a much more complex muscular architecture than their adults - they remodel during their metamorphosis. That's a clue that the ancestors had a highly complex muscular bodyplan. Their findings are published in the current issue of the scientific journal "Current biology". With over 200.000 species described, the Mollusca - soft-bodies animals that, among others, include snails, slugs, mussels, and cephalopods - constitutes one of the most species-rich animal phyla. What makes them particularly interesting for evolutionary studies, however, is not the sheer number of their representatives, but rather their vast variety of body morphologies they exhibit.