STUDIES ON THE GROWTH OF INTEGUMENTARY PIGMENT IN THE LOWER VERTEBRATES

II. THE RÔLE OF THE HYPOPHYSIS IN MELANOGENESIS IN THE COMMON CATFISH (AMEIURUS MELAS)

¹ From the Department of Anatomy, The Ohio State University

The common catfish (Ameiurus mclas) possesses naturally a white vest ventrally in which melanophores are only rarely found. In appropriate apparatus it is possible to grow melanophores abundantly over this naturally unpigmented area and increase the amount of pigment in other areas if the dorsal aspect (normally pigmented surfaces) of the fish is maintained in the dark phase. It is convenient, though not necessary, to continue the dark phase permanently by blinding the fish totally, a fact which "per se" indicates that the eyes are not necessary in active melanogenesis.

If the pituitary gland is removed, however, melanogenesis does not continue. In fact, melanophore degeneration sets in with the end result that the experimental fish is paler and less heavily melaninated than stock controls. This indicates that the melanophore-dispersing hormone of the pituitary gland so important in the normal color change physiology of the catfish is also indispensable to the development and maintenance of melanin in melanophores. Interpreted in another way, it suggests that morphological color change is not produced by physiological color change but rather that both are the result of a common underlying mechanism.

A possible way in which the melanophore-dispersing fraction of the pituitary may be involved in the production of melanin is discussed. It is suggested that the melanophore-dispersing hormone (intermedin) in the human hypophysis may be concerned in the production and maintenance of normal pigmentation in man.