Phase delay of the natural photoperiod alters reproductive timing in the marsupial Antechinus stuartii

Abstract

The dasyurid marsupial Antechinus stuartii (20–40 g) has a brief, highly synchronized mating period in spring followed by complete male mortality. Analysis of breeding times in nature suggests that the rate of change of photoperiod is the main Zeitgeber for reproductive timing in this species. To test this hypothesis the natural photoperiod was phase delayed by two months, one experiment beginning in late summer, and the other in the autumn, before the spring breeding period. The reproductive cycle of males and females exposed to the delay in summer was synchronously delayed by two months, coincident with the exact duration of the delay. Animals exposed to the two month phase delay in autumn also exhibited a delay in reproductive timing, but it was less synchronized than either the control or the other experimental group. Reproduction in control animals exposed to natural photoperiod was synchronous with that of a wild population monitored simultaneously. It is therefore likely that the rate of change of photoperiod is the dominant Zeitgeber for the reproductive cycle in this species.

Daily torpor in a pregnant dunnart (Sminthopsis macroura Dasyuridae: Marsupialia)

“…We studied 12 adult, female S. macroura (body mass 24:0 AE 3:0 g) that were captivebred at the University of New England in Armidale. Individual reproductive condition was classified following McAllan et al (1991). When exhibiting oestrus, each female was paired with a male for the duration of the oestrous period.…”

Photoperiod and the timing of reproduction in Antechinus flavipes (Dasyuridae: Marsupialia)

“…Females were checked once every 1-2 weeks and during the mating season every 2-3 days, for the presence of epithelial cells, which indicate the onset of oestrus (Selwood 1982;McAllan et al 1991). Urine samples were taken when possible.…”

“…Dickman (1985) found that the laboratory conditions of his study also affected reproductive synchrony under both naturally changing and LD 12:12 photoperiod, indicating an effect of social organization. McAllan and Dickman (1986) and McAllan et al (1991) demonstrated that a discretely increasing photoperiod (rate of change of photoperiod) may synchronize reproduction in A. stuartii.…”

“…Females are monoestrous and all males die shortly after mating (Woolley 1966;Wood 1970). While the pattern of the reproductive behaviour has been extensively monitored, little work has been done to establish the mechanisms by which reproduction is controlled (Dickman 1985;Scott 1986;Woolley 1966;Wood 1970;McAllan et al 1991). Most work has focused on members of the A. stuartii/A.…”

“…Most work has focused on members of the A. stuartii/A. agilis complex with few studies exploring mechanisms of regulation of the reproductive cycle in other species (Dickman 1985;Scott 1986;Woolley 1966;Wood 1970;McAllan et al 1991). Dickman (1985), on the basis of experimental evidence, has suggested that photoperiod may cue an endogenous rhythm in three species of Antechinus.…”