Effects of surgical deafening and exposure to continuous darkness on cloacal gland size in scotorefractory Japanese quail

Abstract

Adult male quail were transferred to short days (SD) and exposed simultaneously to conspecific vocalizations of males on long days (CVMLD). Cloacal glands did not regress in some males while in others their glands regressed then spontaneously recrudesced. Of the birds that exhibited cloacal gland regression, 80% recrudesced by 8 weeks and all birds recrudesced by 25 weeks on SD. Three experiments are reported. The first experiment analyzed the effects of transfer to SD. The remaining two experiments examined the role of auditory stimuli. In Experiment 2, deafening males whose cloacal glands had not regressed after 17 days exposure to SD and CVMLD produced a significant decrease in cloacal gland size. In Experiment 3, quail whose cloacal glands had regressed and recrudesced while exposed to SD and CVMLD were deafened and/or transferred to complete darkness (DD). Cloacal gland size was significantly smaller in deafened males kept on SD or kept in DD than in sham controls retained on SD. Surprisingly, the cloacal glands of sham controls in DD were similar to those of intact birds which remained on SD. These results suggest that scotorefractoriness which has been attributed to an insensitivity to short photoperiods may be due to a sensitivity to vocalizations of birds on LD. Perhaps there is a hierarchy of physical and social cues so that a decrease in the photoperiod unmasks the effects of auditory stimuli. Furthermore, an interval timer mechanism or some alternative to the external coincidence model of time keeping seems to account for the refractoriness to SD.