Starfish embryos can organise themselves into large, oscillating crystals at the surface of water. These structures, which had never been seen before, may form because of the embryos鈥� swimming style and body shape.
at the Massachusetts Institute of Technology and her colleagues placed hundreds of starfish embryos, each around 0.1 millimetres in size, in small, salt-water tanks. The embryos then arranged themselves into honeycomb-like patterns at the water鈥檚 surface. This 鈥渓iving crystal鈥� was a pulsating hexagonal grid with the round-shaped embryos jiggling in their positions.
The researchers noticed the living crystal while they were breeding starfish embryos with the intention of studying the small water currents and vortices they create while swimming. 鈥淲e were totally not expecting this. We really were interested in how the starfish embryos swim differently as they develop and change shape,鈥� says co-author at the Max Planck Institute of Molecular Cell Biology and Genetics in Germany.
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Starfish embryos resemble round particles covered in hair-like appendages, which they use to move forward and spin around. When they form the living crystal, the embryos clump together and can still spin, but not swim away. Just as the atoms in an ordinary crystal are arranged in repeating patterns, embryos in the living crystal form repeating hexagons.
at Stanford University in California says that such a living crystal wouldn鈥檛 naturally form in the ocean as starfish embryos are normally enveloped in water and aren鈥檛 near the surface.
As the embryos mature, they get less round and more elongated, which makes them better at breaking away from water currents and swimming away from the surface. Accordingly, after a couple of days, the team observed the living crystals breaking apart.
at Clark University in Massachusetts says he is curious about what the living crystals can reveal about design principles in ecology and biology.
Some bacteria have been observed self-organising into ordered clusters, and Tan says that the team is now studying different starfish species, as well as considering some species of sea urchins, to see if they do the same.
Beyond the basic physics, the team isn鈥檛 sure why the embryos group as they do. 鈥淏iologically, why do these embryos make these very striking crystals? That鈥檚 the next big question,鈥� says Tan.
Nature
