Sensitivity of winter flounder melanophores after removal of the epidermis from in vitro preparations

Winter flounder Pleuronectes americanus has a thick epidermis which was removed from scale slips by incubation in a medium including 1% ethylenediaminetetraacetic acid (EDTA) for up to 2 h. Neurally mediated responses of dermal melanophores to K+ and Na+, and to exogenous noradrenaline (10‐5 M) were 1·5 to three times faster without the epidermis–mucus barrier; α‐melanophore stimulating hormone (MSH) evoked extensive pigment dispersion only without the epidermis. Thus, cellular viability after epidermal removal is not restricted to melanophores, nerve terminals can provide an additional indicator. The sensitivity to α‐MSH in vitro, is an important observation since in vivo reports have not indicated that this hormone has a role in the physiological responsiveness of these melanophores in flatfish.