Proceedings of The Physiological Society

University of Manchester (2010) Proc Physiol Soc 19, PC41

Poster Communications

Coupled ensembles III: power spectrum of excitatory waves in the skin of Loligo vulgaris.

A. Packard1,2

1. Home, La Garde-Freinet, France. 2. Stazione Zoologica ?ǣAnton Dohrn?ǥ, Naples, Italy.

  • Thresholded pigment spots from two superimposed video-frames of the mantle of an adult squid (Loligo vulgaris) 7d after unilateral denervation. Grey profiles, spots during FWD propagation (see text); black, same spots at rest (fully retracted). Yellow spots not shown.

  • Ratio of expanded to resting size (E/r = responsiveness) of same spots at peak-expansion within the wave front (see Fig. 1a).

Coloured fast waves of excitation (FW) run across the skin of octopuses, squids and cuttlefish when conditions suppressing such spontaneous activity (automaticity) have been removed or reduced in some way. One of these conditions is presence of nerves. This poster uses image analysis (ImageJ) to assess relative power distribution within regular FW that develop on one side of the mantle of a squid Loligo vulgaris several days after surgical interruption of the nerve supply (anaesthetic: 1% ethyl alcohol in seawater). FW propagate differentially through the chromatophore layers probably via interstitial cells (Mackie, 2008) reminiscent of ICC (interstitial cells of Cajal). Chromatophore organs (spots), characterized by the size and colour of their pigment spots, are powered by a halo of transparent muscle fibres; when maximally extended in the viewing plane, by what seem to be synchronous single twitches of their radial muscle fibres, ratios of expanded to resting area (E/r) for red and brown classes are approximately 15:1 (separate findings). Relative power generated amongst spots of different size/colour classes during entrainment by the wave, has been approximated by dividing degree of active expansion (flattening) of individual spots at peak expansion with their size in the trough of the wave (fully retracted, spherical, state). (N.B. ideally, power [rate of doing work] is represented by the area [in pixels] under the curve of expansion and retraction of individual chromatophore organs over time). Figure 1a is from a long recording session (see movie) of regular fast waves (FW) generated from foci out of the picture. Velocities at the wave front are c. 1cm/s. Yellow waves (FWD) propagate through yellow spots, and dark waves (FWD) are mixed waves that entrain red and brown spots of several size/colour classes. FWD and FWY travel separately from each other and do not interfere; FWD from two different foci cancel each other out when they collide. (Yellow spots lie in the uppermost stratum of the chromatophore layer of the skin, red and brown spots are below them: largest [oldest] in the deepest stratum, smallest [youngest] lie near yellow spots of the upper layers). During FWD, E/r for individual spots at peak expansion within the wave is a function of resting size (Fig. 1b): smallest spots least activated, largest most. Some of the largest spots (‘nuclear oscillators’) have a life of their own; they are not entrained. These experimental data highlight gaps in our knowledge of coupled ensembles; ‘spreading depression’ in the skin of squids has an epigenetic signature.

Where applicable, experiments conform with Society ethical requirements