RESPONSES OF DEEP-SEATED MELANOPHORES IN FISHES AND AMPHIBIANS

¹ From the Zoölogical Laboratories, Radcliffe College

In frogs, the deep-seated melanophores of the fascia of the leg muscles, of the muscles of the back, of the muscles of the body wall, of the mesenteries, and of the pleura respond to white or black backgrounds, adrenalin, and pituitrin in the same manner as do those in the skin, but about six times more slowly.

In tadpoles, the deep-seated melanophores of the fascia of the bodywall muscles, of the mesenteries, of the pericardium, and of the pleura respond to white or black backgrounds, adrenalin, and pituitrin in the same manner as do those in the skin, but react about ten times more slowly to the drugs.

In killifish, the deep-seated melanophores of the parietal peritoneum and the connective tissues of the dorsal blood vessels respond to white or black backgrounds, adrenalin, and ether synchronously with those in the skin.

It is suggested that the difference in the speeds of response of the deep-seated melanophores in fishes and in amphibians is dependent upon the two methods of control which exist in the dermal melanophores of these two classes—nervous for fishes and humoral for amphibians.

In amphibians, the difference in the speed of dermal and deep-seated melanophores is believed to be due to the distribution of the blood vessels. While the skin is ramified with small blood vessels, the deep connective tissue receives a relatively scanty supply, for while many large veins and arteries pass through this tissue, they give off few branches to these parts. Also, the less extreme and more variable condition found among the deep-seated melanophores is thought to be caused by a dilution of the activating materials by the lymph.

The similarity of response in the deep-seated and dermal melanophores does not reveal what function these cells may serve.

Although the internal melanophores obviously play no part in color changes, neither does their activity interfere with the usual idea that the function of color changes in the skin is an adaptive one, because they are either so few in number that their role must be slight (fishes), or so sluggish that they seldom reflect the changes of the skin (amphibians).