RELATION OF SURFACE AND VOLUME TO SO-CALLED PHYSIOLOGICAL GRADIENTS IN PLANARIA

The uptake and incorporation of 14C-labeled amino acids into Dugesia dorotocephala have been studied in relation to the regional surface and volume of the animal. The absolute amounts of amino acids entering and/or incorporated are predictable by a power function of the surface-to-volume ratio. The specific activities of the labeled protein fractions are consistent with an axial gradient of protein synthesis. The data do not support differential permeability as a basis for the axial metabolic gradient, but point to a physiological basis rather than a simple physical relation to the environment. © 1969.