About the Authors
Department of Zoology, University of Cambridge, Cambridge, United Kingdom
Department of Bioengineering, Imperial College London, London, United Kingdom
Division of Biology, California Institute of Technology, Pasadena, California, United States of America
The authors have declared that no competing interests exist.
SJH and HGK conceived and designed the experiments. SJH performed the experiments and analyzed the data. SJH and HGK wrote the paper.