MECHANISM OF PIGMENT DISPLACEMENT IN UNICELLULAR CHROMATOPHORES

Abstract

Increasing hydrostatic pressure progressively inhibits the conc. of melanophore pigment, at least roughly in proportion to the magnitude of the pressure, in the range up to 7000 pounds/ square inch. At each higher pressure the capacity to contract is further reduced, not only in the case of pulsating melanophores (Spaeth method), but also in the case of steady contractions induced by various chemical agents. This action of pressure is entirely independent of the nerve supply of the melanophores, since denervation does not in any way alter the pressure responses of the pigment cells. Low temp. (6[degree]C.) reinforces the pressure inhibition of contraction, but high temp. (30[degree]C.) has a counteracting effect. Both the pressure and the temperature effects indicate that contraction depends upon the capacity of the protoplasm of the pigment cells to undergo gelation; whereas expansion involves solation. This hypothesis, which is borne out by a number of microscopic observations, brings melanophore activity into line with several other types of protoplasmic movement.