23 August 2001

Biophysics: Dual-function biomaterial in focus

Certain brittlestars are extremely light-sensitive, able to detect shadows from a distance and thereby escape from predators by seeking shelter. One explanation for this capability is now found in their arm ossicles, which are single calcite crystals serving not only as skeletal armour, but also as arrays of microlenses. The lenses act in concert with photoreceptors and chromatophores and form aberration-free, photochromic compound-eye units. This remarkable biomaterial gives scientists developing multifunctional 'smart' materials something to aim for. On the cover such a brittlestar is shown against an arm ossicle with the array of microlenses.

Calcitic microlenses as part of the photoreceptor system in brittlestars
JOANNA AIZENBERG, ALEXEI TKACHENKO, STEVE WEINER, LIA ADDADI & GORDON HENDLER
Nature 412, 819-822 (23 August 2001)
| First Paragraph | Full Text | PDF (432 K) |

Optics: Armed for light sensing
ROY SAMBLES
A remarkable array of microlenses formed from calcite has been found on a species of brittlestar. These lenses appear to be responsible for the brittlestar's sensitivity to light.
Nature 412, 783 (23 August 2001)
| Full Text | PDF (63 K) |

Eyes in their stars

23 August 2001 table of contents