| dc.description.abstract |
The southern snow skink, Niveoscincus microlepidotus,exhibits an unusual biennial reproductive cycle with an extended gestationperiod of approximately 1 year. Morphological data were gathered on a monthlybasis, providing a detailed picture of the reproductive cycle. Vitellogenesisbegins in spring, immediately after parturition. Maximum follicular diameteris reached before the winter hibernation period and ovulation occurs thefollowing spring. Embryos are fully developed and reach maximum size by earlyautumn. Yolk reserves are depleted before winter. Birth of between one andfour young occurs the following spring. Plasma progesterone concentrations arelow (2.7 ± 0.9 ng mL-1) in post-partum females,begin to rise in autumn in vitellogenic females and peak (38.5 ± 7.9 ngmL-1) in pre-ovulatory females after hibernation.Concentrations are high (15.4 ± 5.9 ng mL-1) inearly pregnancy and decline to basal levels before winter and well beforebirth in spring. Plasma oestradiol concentrations peak during vitellogenesis(1.0 ± 0.3 ng mL-1) and decline to basal levelsduring pregnancy (0.2 ± 0.03 ng mL-1). A secondoestradiol peak occurs before parturition (0.7 ± 0.2 ngmL-1). Thus, functional completion ofvitellogenesis and gestation is achieved by autumn in successive years. Themechanisms that defer ovulation and parturition by a further six months areunknown.Keywords: biennial reproductive cycle, oestradiol,progesterone, snow skink, Tasmania. |
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