Responses of metamorphosing Taricha torosa to x rays

Abstract

A single dose of 1000 rads of x rays administered to metamorphosing Taricha torosa larvae interferes selectively with some elements of the metamorphosing process without, apparently, affecting any major triggering mechanism. Though the predominant result is a failure to complete metamorphosis, metamorphosed irradiates showing larval pigmentation, vestigial gills, and non-protuberant eyes have been observed. Arrest of the normal thickening of the epidermis during metamorphosis and of the associated development of the epidermal melanophores is followed by regression of the pigment pattern to the larval form. This 1000-rad dose appears to kill half of a sample population in 30 days. A single dose of 200 rads, while allowing completion of metamorphosis, is fatal within some 3 months. The metamorphosed animals show predominantly adult characteristics.