Scientists at the Cambridge University have discovered that freshwater algae can form stable groupings in which they dance around each other, miraculously held together only by the fluid flows they create. Their research was published today in the journal Physical Review Letters.
The researchers studied the multicellular organism Volvox, which consists of approximately 1,000 cells arranged on the surface of a spherical matrix about half a millimetre in diameter. Each of the surface cells has two hair-like appendages known as flagella, whose beating propels the colony through the fluid and simultaneously makes them spin about an axis.
The researchers found that colonies swimming near a surface can form two types of "bound states"; the "waltz", in which the two colonies orbit around each other like a planet circling the sun, and the "minuet", in which the colonies oscillate back and forth as if held by an elastic band between them.
The researchers have developed a mathematical analysis that shows these dancing patterns arise from the manner in which nearby surfaces modify the fluid flow near the colonies and induce an attraction between them. The observations constitute the first direct visualisations of the flows, which have been predicted to produce such an attraction. They have been implicated previously in the accumulation of swimming microorganisms such as bacteria and sperm cells near surfaces.
These findings also have implications for clustering of colonies at the air-water interface, where these recirculating flows can enhance the probability of fertilization during the sexual phase of their life cycle.
Professor Raymond E. Goldstein, the Schlumberger Professor of Complex Physical Systems in the Department of Applied Mathematics and Theoretical Physics (DAMTP) and lead author of the study, said: "These striking and unexpected results remind us not only of the grace and beauty of life, but also that remarkable phenomena can emerge from very simple ingredients."
Funded by the Biotechnology and Biological Sciences Research Council (BBSRC), the work is part of a larger effort to improve our knowledge of evolutionary transitions from single-cell organisms to multicellular ones. This greater understanding of the nature of self-propulsion and collective behaviour of these organisms promises to elucidate key evolutionary steps toward greater biological complexity.
Moreover, the flagella of Volvox are nearly identical to the cilia in the human body, whose coordinated action is central to many processes in embryonic development, reproduction, and the respiratory system. For this reason, the study of flagellar organisation has potentially broad implications for human health and disease.
The group was led by Professor Goldstein and included Ph.D. student Knut Drescher, postdoctoral researchers Drs. Idan Tuval and Kyriacos C. Leptos, Professor Timothy J. Pedley of DAMTP, and Prof. Takuji Ishikawa of Tohoku University, Japan.
For additional information please contact:
Genevieve Maul, Office of Communications, University of Cambridge
Tel: +44 (0) 1223 332300, +44 (0) 1223 765542
Mob: +44 (0) 7774 017464
Notes to editors:
1. The article 'Dancing Volvox : Hydrodynamic Bound States of Swimming Algae' was published today in the journal Physical Review Letters.
2. Video footage and image available upon request. Image and video credit: Please credit Professor Goldstein and Knut Drescher.
3. About BBSRC: The Biotechnology and Biological Sciences Research Council (BBSRC) is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £450 million in a wide range of research that makes a significant contribution to the quality of life for UK citizens and supports a number of important industrial stakeholders including the agriculture, food, chemical, healthcare and pharmaceutical sectors. BBSRC carries out its mission by funding internationally competitive research, providing training in the biosciences, fostering opportunities for knowledge transfer and innovation and promoting interaction with the public and other stakeholders on issues of scientific interest in universities, centres and institutes.
For more information see: http://www.bbsrc.ac.uk
4. Department of Applied Mathematics and Theoretical Physics (DAMTP) has a 50-year tradition of carrying out research of world-class excellence in a broad range of subjects across applied mathematics and theoretical physics. Members of DAMTP have made seminal theoretical advances in the development of mathematical techniques and in the application of mathematics, combined with physical reasoning, to many different areas of science. A unique strength is the G K Batchelor Laboratory, in which fundamental experimental science is also performed. Research students have always played a crucial role in DAMTP research, working on demanding research problems under the supervision of leading mathematical scientists and, in many cases, moving on to become research leaders themselves. The current aims of DAMTP are to continue this tradition, in doing so broadening the range of subject areas studied and using new mathematical and computational techniques.
*** Video available***
Waltzing Volvox: http://www.youtube.com/watch?v=V6Yg2BQy82w&NR=1
Minueting Volvox: http://www.youtube.com/watch?v=QD7HQLhy_IY&feature=channel_page
Physical Review Letters