Emergent motility in macroscopic multicellular snowflake-yeast

The presence of flagella or cilia has long been thought to be essential for the evolution of motility in nascent multicellular systems, such as volvox, or groups of choanoflagellates. Yet, self-propulsion of aquatic organisms, in principle, can arise simply from (self-generated or ambient) fluid flows coupled with shape asymmetry of the organism. Recently we showed that "snowflake yeast", an experimental model for nascent multicellularity, can generate flows in the ambient fluid it is immersed in, via metabolically sustained buoyant plumes. Here, we report that when friction with the substrate is overcome, the snowflake yeast clusters are rendered motile, as a consequence of these fluid flows. Snowflake yeast are able to disperse themselves over multiple body lengths in metabolically active media without the presence of flagella or cilia. Further, our observations indicate a tradeoff between motility and the growth of the clusters, potentially providing a template for the emergence of a primitive life cycle and population dispersal mechanism.