Molting and its hormonal control in toads

Abstract

A description is given of molting in normal toads, Bufo bufo (L.), and in toads with pars distalis of the hypophysis extirpated. Normal toads molted every seventh to eleventh day, at 20°–23°C, with no significant seasonal variation. Change of environment often suppressed molting for a few days. Extirpation of the pars distalis increased the frequency of formation and separation of new cornified layers, but suppressed shedding. In toads with extirpated pars distalis, repeated injections of extracts of pars distalis or of DCA caused more or less normal molts, at a frequency of about twice the normal. Usually the time interval between separation and shedding of the cornified layer was abnormally long. Thyroxine did not cause shedding, but shortened the time of survival of the operated toads. Repeated injections of extracts of pars distalis or of DCA into normal toads increased the frequency of molting, and often increased the time interval between separation and shedding of the cornified layer. Thyroxine likewise increased the frequency, but never caused abnormal loosening of the stratum corneum. Some reference is made to the functions of the endocrine system, in molting in vertebrates, from amphibians to mammals.