Photoperiod and the termination of embryonic diapause in the marsupial Macropus eugenii

Abstract

Tammar wallabies show obligate delayed implantation with embryonic diapause terminating at the southern hemisphere summer solstice. Groups of wallabies were placed on normal daylight photoperiod, 15 L:9 D, and 12 L:12 D at the vernal equinox. The last 2 groups were altered to 12 L:12 D and 9 L:15 D, respectively on January 19. A reduction of 3 hours in photoperiod resulted in the termination of embryonic diapause but this occurred independent of the previous light regimen. An analysis of field data suggested that the time of reactivation of development is related to the time of full moon relative to the summer solstice.