We compared the uterine component of the placentae of each placental region of two species of lizards, Eulamprus tympanum and Pseudemoia entrecasteauxii, to identify potential routes and mechanisms of nutrient transport. We focused on the uterine epithelium because nutrients must pass though it to reach the embryo. At this point, we have only been able to study two species in detail, but each has a placenta of different complexity and quantitatively different placentotrophy. The uterine epithelium of the chorioallantoic placenta has a different morphology from the omphaloplacenta, and the chorioallantoic placenta of P. entrecasteauxii, the most placentotrophic of the two species, is further differentiated in placentomal and paraplacentomal regions. The chorioallantoic region of E. tympanum, and the paraplacentomal region of P. entrecasteauxii have morphologies indicative of gas exchange epithelia. The blood-uterine lumen distance in P. entrecasteauxii, however, is about one tenth that in E. tympanum, suggesting a greater diffusive capacity for gases in P. entrecasteauxii. The omphaloplacenta of both species has a similar structure, with hypertrophied cells, electron-dense granules in the apical cytoplasm and vesicles budding off into the uterine lumen. This result is particularly interesting because E. tympanum exhibits little net nutrient transfer to the embryo during pregnancy. Nutrient provision across the omphaloplacenta in both species occurs by histotrophy. The placentome of P. entrecasteauxii also has a morphology suggestive of nutrient provision, but by some non-histotrophic mechanism and may be very important in the evolution of substantial placentotrophy.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.