Does date of birth or a capacity for facultative placentotrophy influence offspring quality in a viviparous skink, Niveoscincus microlepidotus?
Natalia Atkins A , Roy Swain A and Susan M. Jones A BA School of Zoology, University of Tasmania, Private Bag 5, Hobart, Tas. 7001, Australia.
B Corresponding author. Email: s.m.jones@utas.edu.au
Australian Journal of Zoology 54(5) 369-374 https://doi.org/10.1071/ZO06041
Submitted: 18 May 2006 Accepted: 25 September 2006 Published: 16 November 2006
Abstract
Niveoscincus microlepidotus is a viviparous lizard that exhibits biennial reproduction: births in spring optimise offspring survival in this species’ alpine habitat. Over three annual activity seasons, we investigated the hypothesis that date of birth influences offspring characteristics. In the first year of our study, there was no effect of date of birth on any offspring characteristic measured. In the second year, later-born offspring grew significantly faster. In the third year, later-born offspring were significantly longer and heavier at birth. These varying results may be attributable to differences in basking opportunities for the gestating females due to annual variations in spring weather patterns. To test the hypothesis that both lecithotrophic (yolk) and placentotrophic nutrients support embryos during their extended gestation, we determined the degree of placentotrophy for this species. The mean dry neonate : dry egg ratio of 0.755 indicates that this species is predominantly lecithotrophic. Only in the first year of the study did the data suggest a potential for facultative placentotrophy in this species. We therefore suggest that in N. microlepidotus lecithotrophic nutrition is converted into embryonic fat bodies that support the embryo in utero over winter until spring parturition.
Acknowledgments
This work was completed under University of Tasmania Animal Ethics Permit A6940. Animals were collected under permits FA 02153, FA 02223, FA 03175 and FA 04129 from the Nature Conservation Branch, Tasmania, and permits from the Wellington Park Management Trust. Funding was provided by an Australian Research Council Discovery Grant awarded to RS and SMJ. We thank A. Edwards, J. Stuart-Smith, M. Cecil, E. Wapstra, J. McCormack, M. Jahn and the Jones family for help in the field and the laboratory.
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