ABSTRACT
Melanophores of winter flounder (Pseudopleuronectes americanus) subjected to repeated transfers between black and white backgrounds display pronounced enhancement of the rates of melanosome aggregation and dispersion. Melano-some aggregation in response to repeated injection of noradrenaline displays a similar enhancement. In vitro preparations of microscopic skin samples on scales removed during successive cycles of background changes also display increasing melanophore response rates to K+ stimulation. It is concluded that a physiological ‘priming’ mechanism is involved peripherally at the melanophore level and it is proposed that this represents a form of facilitation. Also, it is deduced from these experiments that a modulation of the microtubular channels associated with melanosome translocation is probably the basis of the facilitation process.
