Two decades ago, Michael Schrödl, curator of the mollusk compilation at the Bavarian State Collection of Zoology in Munich, Germany, attended a lecture on Salinella salve, a mysterious organism described as a single layer of cells, ciliated on both inner and outer surfaces and surrounding a central hollow sac open at both ends. Its body plan, which suggests a central digestive tract with a mouth and an anus, was unlike that of any known life-form. Composed of just one cell layer, Salinella seemed intermediate between single-celled organisms that perform all digestion inside the cell, and multicellular life-forms that excrete digestive juices into a central sac.
Was Salinella a missing link between protozoans and metazoans? A living relic of the transition from single-celled life to more complex forms with multiple cell layers? Schrödl was determined to find out. But there was one major problem—Salinella salve had been collected only once, by ...
