Andrew's Squid Experiments
from a Physical Point of View
The orderly colour changes of cephalopods require an intact brain. When the brain has died, or the nerve supply to the skin has been removed, the colours become chaotic. Such autonomous behaviour highlights a general principle.
Andrew Packard  has observed wave-like excitements flowing through the spots of colour (chromatophores) of squids some days after cutting the nerve to one side of the body. These muscle-operated organs develop supersensitivity and non-nervous communication between them. The different properties can be inspected directly through the transparent surface of the animals' skin.
Squid with centimeter scale
Waves proceeding in a layered 'neural' wave space show relations within a single layer and between different layers. Black, red and yellow chromatophores act relatively independently of each other, and with different conductivities in the separate layers.
Besides straight-going waves proceeding from boundaries with innervated skin, we find circular waves radiating from a centre of irritation and spiral waves rotating around a stable core.
Water temperature influences the waves. Below 6°C they are abolished. Above 10°C, frequency, velocity and numbers of waves differentially increase.
Deletion of two colliding waves shows, that 1) the conductivity mechanism acts multidirectionally; 2) disappearance of waves behind the points of interference means that the wave space is cleaned during a chromatophore's refractory period.
In physical terms these findings have some consequences:
- we find delayed excitement of chromatophore cells,
- we find comparable time-functions (near Gausian wave) on each chromatophore cell,
- the mechanism of excitement is delayed (by whatever),
- we find wave propagation,
- we find wave-deletion,
- velocity and direction of interfering excitement can be seen as vector sum of the partial velocities,
- it is possible to force wave velocities higher then medial velocities (resulting wave vector).
- the abstraction of mechanism is called "Interference Network" (IN; flowing time-functions on nets),
- the effect of wave deletion can not be modeled using homogenuous, global, non-cellular circuits,
Thanks to Andrew Packard for lots of interesting discussions in the special field.
[AP1995] Packard, A.: Organization of cephalopod chromatophore systems: a neuromuscular image-generator. In: Abbott, N.J., Williamson, R., Maddock, L., Cephalopod Neurobiology, Oxford University Press, 1995, pp. 331-367
[AP2001] Packard, A 'neural' net that can be seen with the naked eye In : Backhaus. W. (ed) 2001 International School of Biocybernetics (Ischia): Neuronal coding of perceptual systems: pp. 397-402. World Scientific, Singapore, New Jersey, London, Hong Kong, see http://gilly.stanford.edu/APackardneuralnet.pdf
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File created Nov. 24, 1998 gh/ap; upgraded.
since aug. 17, 1999