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Delayed ovulation and parturition in a viviparous alpine lizard (Niveoscincus microlepidotus): morphological data and plasma steroid concentrations
journal contribution
posted on 2023-05-16, 13:37 authored by Girling, JE, Susan JonesSusan Jones, Swain, RThe southern snow skink, Niveoscincus microlepidotus, exhibits an unusual biennial reproductive cycle with an extended gestation period of approximately 1 year. Morphological data were gathered on a monthly basis, providing a detailed picture of the reproductive cycle. Vitellogenesis begins in spring, immediately after parturition. Maximum follicular diameter is reached before the winter hibernation period and ovulation occurs the following spring. Embryos are fully developed and reach maximum size by early autumn. Yolk reserves are depleted before winter. Birth of between one and four young occurs the following spring. Plasma progesterone concentrations are low (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 ng mL–1) in pre-ovulatory females after hibernation. Concentrations are high (15.4 ± 5.9 ng mL–1) in early pregnancy and decline to basal levels before winter and well before birth in spring. Plasma oestradiol concentrations peak during vitellogenesis (1.0 ± 0.3 ng mL–1) and decline to basal levels during pregnancy (0.2 ± 0.03 ng mL–1). A second oestradiol peak occurs before parturition (0.7 ± 0.2 ng mL–1). Thus, functional completion of vitellogenesis and gestation is achieved by autumn in successive years. The mechanisms that defer ovulation and parturition by a further six months are unknown.
History
Publication title
Reproduction Fertility and DevelopmentVolume
14Pagination
43-53ISSN
1031-3613Department/School
School of Natural SciencesPublisher
CSIRO PublishingPlace of publication
AustraliaRepository Status
- Restricted