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Research Article
Placental specializations of the mountain spiny lizard Sceloporus jarrovi
Article first published online: 11 JUN 2010
DOI: 10.1002/jmor.10860
Copyright © 2010 Wiley-Liss, Inc.
Additional Information
How to Cite
Blackburn, D. G., Gavelis, G. S., Anderson, K. E., Johnson, A. R. and Dunlap, K. D. (2010), Placental specializations of the mountain spiny lizard Sceloporus jarrovi. J. Morphol., 271: 1153–1175. doi: 10.1002/jmor.10860
Publication History
- Issue published online: 9 SEP 2010
- Article first published online: 11 JUN 2010
- Manuscript Accepted: 19 OCT 2009
- Manuscript Revised: 14 OCT 2009
- Manuscript Received: 8 JUL 2009
Funded by
- Howard Hughes Medical Institute. Grant Number: 52005203
- Faculty Research Grants from Trinity College
- Thomas S. Johnson Distinguished Professorship funds
- Abstract
- Article
- References
- Cited By
Keywords:
- placenta;
- viviparity;
- fetal membranes;
- chorioallantois;
- yolk sac
Abstract
The lizard Sceloporus jarrovi (Phrynosomatidae) is one of the most widely studied viviparous reptiles of North America. Past research has assumed that placentation in this species is relatively simple and functions mainly in gas exchange. Our examination of the late stage placenta via transmission electron microscopy reveals that S. jarrovi has a unique combination of placental characteristics, with unusual specializations for secretion and absorption. In the chorioallantoic placenta, chorionic and uterine tissues are directly apposed through eggshell loss, and their epithelia are greatly attenuated, enhancing gas exchange; this placenta shows evidence of both nutrient transfer and endocrine function. Contrary to past inferences, a yolk sac placenta forms from the avascular omphalopleure and persists through the end of gestation. The uterine epithelium is enlarged and secretory, and the fetal omphalopleure shows branching absorptive channels and other specializations for uptake. Elsewhere, the omphalopleure develops elongated folds that protrude into a coagulum of degenerating shell membrane and other organic material. Uterine tissue in this region shows specializations for absorption. Placental features in S. jarrovi have unexpected functional implications, and challenge assumptions that specializations for nutrient transfer are confined to matrotrophic species. J. Morphol. 271:1153–1175, 2010. © 2010 Wiley-Liss, Inc.