DYE-COUPLING IN THE MUSCLES CONTROLLING SQUID CHROMATOPHORE EXPANSION

Dye coupling between the cone-shaped radial muscle fibres, which contr ol the expansion and closing of a squid chromatophore organ, was inves tigated in the squid Loligo vulgaris. Particular attention was paid to the role of the myomuscular junctions located between the muscle fibr es. Lucifer Yellow was injected ionophoretically into single muscle fi bres under normal artificial sea water (ASW) and under various concent rations of calcium in ASW, Under ASW, 44% of muscle fibres examined we re dye-coupled, 82% were coupled under calcium-free sea water and 67% were coupled under sea water containing high concentrations of calcium . Dye transfer was blocked by octanol, Muscle fibres were never seen t o link adjacent chromatophore organs, Results are discussed in terms o f the role of the myomuscular junctions in the regulation of chromatop hore expansion in the living animal.