Invasive implantation and intimate placental associations in a placentotrophic african lizard, Trachylepis ivensi (scincidae)

  title={Invasive implantation and intimate placental associations in a placentotrophic african lizard, Trachylepis ivensi (scincidae)},
  author={Daniel G. Blackburn and Alexander F. Flemming},
  journal={Journal of Morphology},
In the viviparous lizard Trachylepis ivensi (Scincidae) of central Africa, reproducing females ovulate tiny ∼1 mm eggs and supply the nutrients for development by placental means. Histological study shows that this species has evolved an extraordinary placental pattern long thought to be confined to mammals, in which fetal tissues invade the uterine lining to contact maternal blood vessels. The vestigial shell membrane disappears very early in development, allowing the egg to absorb uterine… 

Prenatal regression of the trophotaenial placenta in a viviparous fish, Xenotoca eiseni

Analysis of the trophotaeniae using the goodeid fish species Xenotoca eiseni suggests that the troPHotaenia is rapidly resorbed by apoptosis in the last phase of the pregnancy and that its circulatory pathway is maintained.

Novel placental structure in the Mexican gerrhonotine lizard, Mesaspis viridiflava (Lacertilia; Anguidae)

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The chorioallantoic placenta is anatomically specialized for maternal–fetal gas exchange, and its expansion during development reflects the growing needs of the fetus for gas exchange.

Mother-to-embryo vitellogenin transport in a viviparous teleost Xenotoca eiseni

The data suggest that the yolk protein is one of the matrotrophic factors supplied from the mother to the intraovarian embryo during gestation in X. eiseni, and levels are elevated during oogenesis.

Placentation in watersnakes II: Placental ultrastructure in Nerodia erythrogaster (Colubridae: Natricinae)

Ultrastructure of the placental tissues from redbelly watersnakes was analyzed during late pregnancy to provide insight into placental development and function and indicates that placental features of this species are consistent with those of other thamnophines, and are evolutionarily convergent on snakes of other viviparous clades.

Fetal Membrane Ultrastructure and Development in the Oviparous Milksnake Lampropeltis triangulum (Colubridae) with Reference to Function and Evolution in Snakes.

A comparison of the fetal membranes of oviparous reptiles to those of other squamate species reveals characteristics that are probably ancestral for snakes, some of which are plesiomorphic for Squamata.

Uterine and eggshell modifications associated with the evolution of viviparity in South American water snakes (Helicops spp.)

The hypothesis that eggshell thinning is associated with the evolution of viviparity and that such thinning result from a reduction in gland size in vivIParous taxa is supported.

Development of yolk sac and chorioallantoic membranes in the Lord Howe Island skink, Oligosoma lichenigerum

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Evolution of mammalian pregnancy and the origin of the decidual stromal cell.

Support for the hypothesis that the decidual cell is a distinct cell type rather than a modulation of endometrial fibroblasts is provided is the origin of derived transcription factor interactions that are necessary for the regulation ofdecidual gene expression, in particular the interactions between HOXA11 and CEBPB with FOXO1A.



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The discovery of five distinct placental arrangements in this species, three of which are transitory and two of which have not been recorded in reptiles, emphasizes the need for accounts that specify ontogenetic stages and the precise identity and composition of squamate placental membranes.

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The chorioallantoic placenta of M. heathi and its relatives warrants recognition as a new morphotype for reptiles, defined here as the “Type IV” placente, the first new type of chorio allantois to be defined formally for reptiles in over half a century.

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The structural features of the uterine epithelium of the chorioallantoic placenta and omphalloplacenta in the viviparous Australian skink, Pseudemoia entrecasteauxii, were investigated using SEM and

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The presence of cytoplasmic vesicles, ribosomal ER, and mitochondria in the chorionic and uterine epithelial cells are consistent with the possibility of additional forms of placental exchange.

Chorioallantoic placentation in squamate reptiles: Structure, function, development, and evolution

Phylogenetic analyses suggest that placental organs have originated on more than 100 occasions among squamate reptiles, and indicate that three separate lineages have converged on substantial placentotrophy through the evolution of specialized histotrophic placentae.

Placental specializations of the mountain spiny lizard Sceloporus jarrovi

The 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.

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Morphologically, the mature placentae of C. chalcides are among the most specialized to have been described in reptiles, reflecting the substantial maternal‐fetal nutrient transfer that occurs in this species.