The influence of photoperiod on the reproductive activity of female Honey possums, Tarsipes rostratus (Marsupialia: Tarsipedidae): assessed by faecal progestagens and oestradiol-17beta.
Six female Honey possums were kept on a 15L:9D light regime to simulate a long daylength over summer. After seven weeks, three females (Group 2) were changed to a shorter daylength of 10L:14D, while the other three females (Group 1) were maintained on the long daylength. Faecal oestradiol-17beta and progestagen levels were measured during the experiment to detect any changes in reproductive rhythm, such as resumption of blastocyst development. Group 2 females were found to have very large and greatly expanded blastocysts with significantly higher levels of progestagens after the change to short photoperiod (p<0.05). In contrast, the Group 1 females had very small diapausing blastocysts and progestagen levels did not change throughout the study. Overall oestradiol levels also increased significantly in Group 2 females (p<0.05) but not in Group 1 females. These results demonstrate that a change from long to short days stimulates increased progestagen output (and oestradiol-17beta to a lesser extent) that supports the growth and expansion of the blastocysts. Photoperiod, in particular its change to a shortening daylength, appears to be a stimulus for terminating diapause in the Honey possum during its first reproduction of the year. However, as subsequent breeding later in the year occurs when daylength is increasing, a similar role for photoperiod cannot be attributed and females may be entrained to other factors such as food resources.
Oates
J E
JE
School of Animal Biology and Centre for Native Animal Research, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia. joates@cyllene.uwa.edu.au
Bradshaw
F J
FJ
Bradshaw
S D
SD
D000818:Animals; D001755:Blastocyst; D004032:Diet; D004958:Estradiol / Q000032:analysis*; D005243:Feces / Q000737:chemistry; D005260:Female; D008394:Marsupialia / Q000502:physiology*; D017440:Photoperiod; D011372:Progestins / Q000032:analysis*; D012098:Reproduction / Q000502:physiology*; D012621:Seasons
D011372:Progestins; D004958:Estradiol