Blackburn, D.G.
(1993). Histology of the
late-stage placentae of the
matrotrophic skink Chalcides chalcides (Lacertilia:
Scincidae). Journal of
Morphology 216: 179-195.
Abstract:
Examination of late-stage placental material of the lizard Chalcides
chalcides from the Hubrecht Laboratorium (Utrecht, Netherlands) reveals
several cytological and histological specializations that appear to have been
superimposed over a morphological pattern that is typical for squamates. The chorioallantoic placenta is highly
vascularized and consists of a single mesometrial placentome and a generalized
para-placentomal region, both of which are epitheliochorial. The placentome is deciduate, and contains
deeply - interdigitating folds of
hypertrophied uterine and chorioallantoic tissue. Chorionic epithelium lining the placentome comprises enlarged,
microvilliated cells, a small proportion of which are diplokaryocytes. The placentomal uterine epithelium is not
syncytial, and consists of enlarged cells bearing microvilli.
The yolk-sac placenta is a true omphaloplacenta (sensu stricto),
being formed by juxtaposition of uterine tissues to an avascular, bilaminar
omphalopleure. Epithelium of the
omphalopleure is stratified, and is hypertrophied into papillae that project
into detritus of the uterine lumen. The
omphalopleure is separated from the yolk sac proper by a yolk cleft that is not
confluent with the exocoelom and not invaded by the allantois. Neither an omphalallantoic placenta nor a
true choriovitelline placenta are present in late gestation.
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.
Reprints: daniel.blackburn@mail.trincoll.edu