The effect of acoustic stimuli on the testis volume and size of the interstitial cells and their nuclei was studied. Two different synthetic calls were used, both with the time pattern of the species-specific mating call: one at the natural frequencies, the other at 1,100 Hz (a major component of the territorial and release call). Exposure to 1,100 Hz resulted in diminished size of the interstitial cells and their nuclei, implying a reduction in androgen production. By contrast, presentation of the synthetic mating call maintained the function of the androgen system, so that the rate of production of androgen hormones and thus the sexual stimulation of the frog remained high. The role of the endocrine system in auditory communication among grass frogs in particular, and anurans in general, is discussed.
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