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 [1] 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

Observations

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 6C they are abolished. Above 10C, 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.

Picture sequence

Fig.1: A black colour wave moves along the denervated side of a squid

Downloadable Movies

Experiments done May, 31st 1995:

Fig.2: Pressure induced waves moving from left (head) to right

Fig.3: Circular waves coming from center region





Experiments done October, 27th 1995:

Fig.4: Straight going waves from left (head) to right

Fig.5: Circular waves coming from center region

Fig.6: Clockwise turning spiral waves

Fig.7: Anti-clockwise turning spiral waves

Fig.8: Slower wave movement induced by cold water (8C)

Fig.9: Externally stimulated circular wave

Fig.10: Yellow and black colour waves moving independently with only weak influence on each other

Fig.11: Deleting waves produced by wave collision

Fig.12: Deleting and diverging waves produced by collision, velocity vector addition

Conclusion

• a) the effect of wave deletion can not be modeled using homogenuous, global, non-cellular circuits (used by the Interference Transformation),
• b) velocity and direction of interfering excitement is the vector sum of the partial velocities,
• c) it is possible to force wave velocities higher then medial velocities (resulting wave vector).

Acknowledgement

[1] 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

Mail to G. Heinz: heinz@gfai.de
Mail to A. Packard: andrew@packards.de

Return to Heinz' homepage: Table of contents: http://www.gfai.de/~heinz

(c) Copyrights: for the text: G. Heinz; for pictures and movies: A. Packard
File created Nov. 24, 1998 gh/ap; cont. upgraded

Access no. since aug. 17, 1999

Some additional discussions (March 2005).