Light response of cultured melanophores of a teleost adult fish, <i>Oryzias latipes</i>

Abstract

Abstract Melanophores of adult fish of Oryzias latipes in culture exhibited light‐sensitivity. They responded with pigment aggregation to darkness, and with dispersion to light. These responses, which could be repeated more than several times by changing the light intensity, were not affected by α‐ or β‐adrenergic blockers. These facts suggest that melanophores of Oryzias directly respond to light with pigment displacement. The degree of melanosome translocation was changed depending on the intensity of illumination. The most effective wavelength for the induction of melanosome dispersion was near 415 nm, and light with wavelength around 550 nm was scarcely effective. Theophylline (2mM) and cyclic AMP (50 μM) inhibited dark‐induced melanosome aggregation. Such inhibition suggests that light may act as a trigger to induce changes in the intracellular levels of cyclic AMP. Seasonal variation was observed in the light‐sensitivity of melanophores in culture; dark‐induced melanosome aggregation was less significant in winter. These facts suggest that a photoreceptive substance may play a role in the light‐sensitivity of melanophores as a trigger to induce the aggregation of melanosomes.