The structure-function relationships of a natural nanoscale photonic device in cuttlefish chromatophores.
Cuttlefish, Sepia officinalis, possess neurally controlled, pigmented chromatophore organs that allow rapid changes in skin patterning and coloration in response to visual cues. This process of adaptive coloration is enabled by the 500% change in chromatophore surface area during actuation. We report two adaptations that help to explain how colour intensity is maintained in a fully expanded chromatophore when the pigment granules are distributed maximally: (i) pigment layers as thin as three granules that maintain optical effectiveness and (ii) the presence of high-refractive-index proteins-reflectin and crystallin-in granules. The latter discovery, combined with our finding that isolated chromatophore pigment granules fluoresce between 650 and 720 nm, refutes the prevailing hypothesis that cephalopod chromatophores are exclusively pigmentary organs composed solely of ommochromes. Perturbations to granular architecture alter optical properties, illustrating a role for nanostructure in the agile, optical responses of chromatophores. Our results suggest that cephalopod chromatophore pigment granules are more complex than homogeneous clusters of chromogenic pigments. They are luminescent protein nanostructures that facilitate the rapid and sophisticated changes exhibited in dermal pigmentation.
Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, , Cambridge, MA 02138, USA.
Leila F
LF
Deravi
Andrew P
AP
Magyar
Sean P
SP
Sheehy
George R R
GR
Bell
Lydia M
LM
Mäthger
Stephen L
SL
Senft
Trevor J
TJ
Wardill
William S
WS
Lane
Alan M
AM
Kuzirian
Roger T
RT
Hanlon
Evelyn L
EL
Hu
Kevin Kit
KK
Parker
D000818:Animals; D002856:Chromatophores / Q000166:cytology / Q000378:metabolism; D049832:Decapodiformes / Q000033:anatomy & histology / Q000502:physiology; D010860:Pigments, Biological / Q000378:metabolism*; D012880:Skin Pigmentation / Q000502:physiology*
D010860:Pigments, Biological
camouflage; cephalopod; chromatophores; photonics; reflectin