About this Environmental Science article
Morphogenesis of placental membranes in the viviparous, placentotrophic lizard Chalcides chalcides (Squamata: Scincidae) by Daniel G. Blackburn; Ian P. Callard is a Environmental Science article available to read on EtoBox.
In the scincid lizard Chalcides chalcides, females ovulate small ova and supply most of the nutrients for development by placental means. The yolk is enveloped precocially by extraembryonic ectoderm and endoderm during the gastrula stage, establishing a simple bilaminar yolk sac placenta. The shell membrane begins to degenerate at this time, resulting in apposition of extraembryonic and maternal tissues. A true chorioplacenta has developed by the early pharyngula stage, as has a choriovitelline placenta and the first stages of an omphaloplacenta. Although the choriovitelline membrane disappears rapidly, the omphaloplacenta spreads to occupy the entire abembryonic pole. The yolk cleft is not confluent with the exocoelom, and no omphalallantoic placenta develops. By the limb-bud stage, an allantoplacenta has been established, with a mesometrial placentome composed of interdigitating ridges of chorioallantois and uterine mucosa. The discovery of five distinct placental arrangements in this species, three of which are transitory and two of which have not previously been recorded in reptiles, emphasizes the need for accounts that specify ontogenetic stages and the precise identity and c
It is typically read by researchers, students, and practitioners in Environmental Science.
- Author
- Daniel G. Blackburn; Ian P. Callard
- Publisher
- John Wiley and Sons; Wiley (John Wiley & Sons); John Wiley & Sons Inc.; Wiley (ISSN 0362-2525)
- Published
- 1997
- Language
- EN
- Field
- Environmental Science (Physical Sciences)