Squids old and young: Scale-free design for a simple billboard

Squids employ a large range of brightness-contrast spatial frequencies in their camouflage and signalling displays.The ‘billboard’ of coloured elements (‘spots’=chromatophore organs) in the skin is built autopoietically–probably by lateral inhibitory processes–and enlarges as much as 10,000-fold during development. The resulting two-dimensional array is a fractal-like colour/size hierarchy lying in several layers of a multilayered network. Dynamic control of the array by muscles and nerves produces patterns that recall ‘half-tone’ processing (cf. ink-jet printer). In the more sophisticated (loliginid) squids, patterns also combine ‘continuous tones’ (cf. dye-sublimation printer).Physiologists and engineers can exploit the natural colour-coding of the integument to understand nerve and muscle system dynamics, examined here at the level of the ensemble. Integrative functions of the whole (H) are analysed in terms of the power spectrum within and between ensembles and of spontaneous waves travelling through the billboard.Video material may be obtained from the author at the above address.