An Oil-Soluble Neurohumour in the Catfish Ameiurus

Abstract

ABSTRACT The skin and fins of Ameiurus, irrespective of their original state, take on the dark coloration (dispersion of melanophore pigment) whenever they are triturated. Hence oil extracts can be made from these parts only in the dark condition. Olive oil extracts from the skin and fins of dark Ameiurus when injected under the skin of light-tinted individuals induce the formation of temporary dark splotches in an otherwise light skin. These splotches result from the dispersion of pigment in the melanophores, both epidermal and dermal, in the region of the injection. On the spontaneous disappearance of these splotches, which ordinarily occurs a few days after their formation, the melanophore pigment reassumes its concentrated state. Newly formed dark splotches in Ameiurus may be obliterated by an injection of adrenalin and will return spontaneously after the adrenalin has disappeared. From these several tests it is concluded that the nervous factor in the dispersion of the melanophore pigment of Ameiurus is an oil-soluble neurohumour of local activity. Ether extractions, hot and cold, yielded residues that were only slightly active in darkening the skin of the catfish. No effective oil extracts could be obtained from the dark skins and fins of Fundulus heteroclitus probably because of the inaccessibility of the tissues to the oil.