Integumentary Pigmentation in Frog During Metamorphosis,with Especial Reference to Tail Skin Histolysis.

Abstract

Several types of larval skin transplantation experiments were made in an attempt to determine the local specificity of frog integument during metamorphosis when transplanted to foreign regions. The grafts involved skin from the back, belly, side and tail. Observations were made with respect to specificity of the integument for pigmentation and histolysis.

Autoplastic and homoplastic larval skin grafts showed local specificity for pigmentation upon larval transformation. All grafts invariably developed the pigment pattern during metamorphosis characteristic of the region from which they had been removed. Skin transplanted from back to side, or side to back, developed normal spotting characteristic of the region from which they had been taken. Skin transplanted from back to belly and vice versa, produced its normal spotting in the new position.

It is concluded that the integument of the frog (Rana pipiens) is specific for pigmentation and the factors responsible for the development of the normal pattern, during metamorphosis, are contained within the skin itself. Moreover, it may be concluded that certain factors within the blood stream are active or become active at a certain stage of metamorphosis and might well be conceived as being responsible for the rapid development of the latent pigmentation pattern present in the various areas of the integument.

Similar transplants involving an interchange of tail skin with skin from the back, suggested a specificity of tail skin toward histolysis. Conversely, skin transplanted from the back to the tail undergoes normal development during metamorphosis and develops the pigmentary pattern characteristic of the region from which it was taken. Instead of such grafts histolyzing and being absorbed due to their contact with atrophying tissues of the tail during metamorphosis, as might be expected, they invariably remained healthy and developed the normal pigment pattern characteristic of back skin. Moreover, the pigmentary changes of such grafts were found to take place simultaneously with the spotting of the back integument. Histological examination showed no signs of cellular histolysis, the integument having the appearance of normal back skin in every respect.