Ontogeny of the extraembryonic membranes of the oviparous lizard,Eumeces fasciatus (Squamata: Scincidae)

Stewart, James R.; Florian, James D.

doi:10.1002/(sici)1097-4687(200005)244:2<81::aid-jmor1>3.0.co;2-d

Cited by 55 publications

(67 citation statements)

References 34 publications

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“…Oviparous embryos exchange oxygen and carbon dioxide across the chorioallantoic membrane, a capillary-dense structure that lines most of the inner surface of the eggshell (Stewart & Thompson 1996, Stewart & Florian 2000. In viviparous species, uterine and chorioallantoic capillaries are closely apposed in the chorioallantoic placenta (Fig.…”

Section: Respiratory Gas Exchangementioning

confidence: 99%

The evolution of viviparity: molecular and genomic data from squamate reptiles advance understanding of live birth in amniotes

2014

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Squamate reptiles (lizards and snakes) are an ideal model system for testing hypotheses regarding the evolution of viviparity (live birth) in amniote vertebrates. Viviparity has evolved over 100 times in squamates, resulting in major changes in reproductive physiology. At a minimum, all viviparous squamates exhibit placentae formed by the appositions of maternal and embryonic tissues, which are homologous in origin with the tissues that form the placenta in therian mammals. These placentae facilitate adhesion of the conceptus to the uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and calcium. However, most viviparous squamates continue to rely on yolk for nearly all of their organic nutrition. In contrast, some species, which rely on the placenta for at least a portion of organic nutrition, exhibit complex placental specializations associated with the transport of amino acids and fatty acids. Some viviparous squamates also exhibit reduced immunocompetence during pregnancy, which could be the result of immunosuppression to protect developing embryos. Recent molecular studies using both candidate-gene and next-generation sequencing approaches have suggested that at least some of the genes and gene families underlying these phenomena play similar roles in the uterus and placenta of viviparous mammals and squamates. Therefore, studies of the evolution of viviparity in squamates should inform hypotheses of the evolution of viviparity in all amniotes, including mammals.Reproduction (2014) 147 R15-R26

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Section: Respiratory Gas Exchangementioning

confidence: 99%

The evolution of viviparity: molecular and genomic data from squamate reptiles advance understanding of live birth in amniotes

2014

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“…Oogonia and oocytes are restricted to the GB, and growing follicles emanate from it. The number of GBs per ovary ranges from one to six among the lizard species studied to date (Jones et al, 1982;Jones and Summers, 1984;Shanbhag and Prasad, 1993;Uribe et al, 1995;Shanbhag et al, 1998;Amey and Whittier, 2000;Stewart and Florian, 2000;Sica et al, 2001). …”

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confidence: 99%

Germinal bed condition in a polyautochronic single-clutched lizard, Bassiana duperreyi (Scincidae)

Radder¹,

Shine²

2007

Amphib Reptilia

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Abstract. In lizards, the eggs are produced within small regions of the ovary known as germinal beds (GBs); previous literature suggests that the number of GBs per ovary may be linked to life-history traits such as clutch size and breeding frequency. In the oviparous montane Australian skink Bassiana duperreyi, females produce a single clutch of 3 to 11 eggs each year. Our histological examination of ovaries of this species revealed a single GB per ovary. In combination with previous studies, our results suggest that scincid lizards may offer ideal model systems to explore the functional link between ovarian morphology and life-history traits in lizards.

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“…Previously, an understanding of fetal membranes in oviparous reptiles stemmed mainly from light microscopic studies on lizards (e.g., Stewart and Thompson, '96;Stewart and Florian, 2000;Stewart et al, 2004a,b). Corn snake eggs are laid at the pharyngula stage, about 6 weeks after mating.…”

Section: Fetal Membranes In An Oviparous Reptilementioning

confidence: 99%

Morphology, development, and evolution of fetal membranes and placentation in squamate reptiles

Blackburn

Flemming

2008

J Exp Zool Pt B

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Current studies on fetal membranes of reptiles are providing insight into three major historical transformations: evolution of the amniote egg, evolution of viviparity, and evolution of placentotrophy. Squamates (lizards and snakes) are ideal for such studies because their fetal membranes sustain embryos in oviparous species and contribute to placentas in viviparous species. Ultrastructure of the fetal membranes in oviparous corn snakes (Pituophis guttatus) shows that the chorioallantois is specialized for gas exchange and the omphalopleure, for water absorption. Transmission and scanning electron microscopic studies of viviparous thamnophine snakes (Thamnophis, Storeria) have revealed morphological specializations for gas exchange and absorption in the intra-uterine environment that represent modifications of features found in oviparous species. Thus, fetal membranes in oviparous species show morphological differentiation for distinct functions that have been recruited and enhanced under viviparous conditions. The ultimate in specialization of fetal membranes is found in viviparous skinks of South America (Mabuya) and Africa (Trachylepis, Eumecia), in which placentotrophy accounts for nearly all of the nutrients for development. Ongoing research on these lizards has revealed morphological specializations of the chorioallantoic placenta through which nutrient transfer is accomplished. In addition, African Trachylepis show an invasive form of implantation, in which uterine epithelium is replaced by invading chorionic cells. Ongoing analysis of these lizards shows how integration of multiple lines of evidence can provide insight into the evolution of developmental and reproductive specializations once thought to be confined to eutherian mammals.

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Ontogeny of the extraembryonic membranes of the oviparous lizard,Eumeces fasciatus (Squamata: Scincidae)

Cited by 55 publications

References 34 publications

The evolution of viviparity: molecular and genomic data from squamate reptiles advance understanding of live birth in amniotes

The evolution of viviparity: molecular and genomic data from squamate reptiles advance understanding of live birth in amniotes

Germinal bed condition in a polyautochronic single-clutched lizard, Bassiana duperreyi (Scincidae)

Morphology, development, and evolution of fetal membranes and placentation in squamate reptiles

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