An Experimental Analysis of the Function of the Pseudobranch in Teleosts

Abstract

1. The effects of removal of the pseudobranch have been studied in four species of marine fish and two species of fresh-water fish. 2. No evidence was found for any direct effect upon osmoregulation or respiratory exchange. 3. Removal of the pseudobranchs was followed by the darkening of the fish, due to chromatophore expansion, and after some weeks, by the degeneration of the choroid gland in the eye. 4. It is suggested that the pseudobranch produces, or activates, a hormone affecting the chromatophores and that the entry of this hormone into the general circulation is controlled by the choroid gland.