Abolition of seasonal embryonic diapause in a wallaby by pineal denervation

Abstract

Embryonic diapause is a widespread phenomenon in mammals and may be controlled either by lactation or by seasonal environmental factors1. A few species, such as the tammar wallaby, Macropus eugenii, use both mechanisms, depending on the time of year. On Kangaroo Island, South Australia (latitude 36° S), female tammars give birth to a single young in late January or early February2. Mating occurs on the day after birth and the resulting conceptus grows to a 100-cell blastocyst before entering a state of embryonic diapause. This arrest of embryonic growth is due to a suppression of the corpus luteum by prolactin induced by the young in the pouch sucking the teat (lactational diapause)3,4. If t..