Tuesday, 26 April 2016

A placenta pioneer from Philadelphia

Newborn and afterbirth of six-banded armadillo
(Euphractus sexcinctus) from Chapman 1901
Some of the earliest studies of placenta in the United States were those of Henry C. Chapman published in Proceedings of the Academy of Natural Sciences of Philadelphia (available on JStor). His observations on the placenta of a six-banded armadillo (Euphractus sexcinctus) were published in 1901 and went unsurpassed for over a century. Importantly, Chapman noted that polyembryony, known from the more widely studied nine-banded armadillo (Dasypus novemcinctus), did not occur in Euphractus.

Fetal membranes of a kangaroo (Macropus giganteus).
Note the small allantois. From Chapman 1881
Chapman is notable for an early study of the fetal membranes of the Eastern grey kangaroo (Macropus giganteus). He noted that there was a large yolk sac but a relatively small allantois that did not form a placenta.

Zonary placenta of an African elephant (Loxodonta africana)
From Chapman c. 1880
Chapman got his armadillo and kangaroo specimens from the Philadelphia Zoo, but his African bush elephant (Loxodonta africana) placenta was from Cooper and Bailey’s London Circus. His was one of several early descriptions of elephant placentation, including a paper by Assheton (here), but there was then a hiatus until the classical work by Amoroso and Perry in 1964 (here). Based on the records of the elephant keeper, Chapman was able to estimate gestation to 650-655 days.

Henry Cadwalader Chapman (1845-1910)
Chapman came from a prominent Philadelphia family. His grandmother was a Biddle and her sister had married a Cadwalader, which may explain his middle name. He studied medicine then spent three years in Europe under Richard Owen in London and Alphonse Milne-Edwards in Paris.

Chapman’s work has been cited by Mossman, Amoroso, Wislocki and Enders (here), but is in danger of being forgotten. When the next paper on Euphractus appeared in 2012 (here), Chapman’s earlier contribution was not acknowledged.

Thursday, 14 April 2016

Placentation in the Tasmanian bettong

Tasmanian bettong (Bettongia gaimardi cuniculus)
By JJ Harrison (CC BY-SA 3.0) via Wikimedia Commons
Now regarded as a subspecies of Eastern bettong (the mainland subspecies is extinct), the fetal membranes of this small kangaroo were described in 1930 by Theodore Thomson Flynn.

Trilaminar omphalopleure (vascular yolk sac) of Tasmanian bettong
From Flynn Proc Linn Soc NSW 1930; 55: 506-531
The yolk sac comprises a vascular portion (trilaminar omphalopleure) and a non-vascular portion (bilaminar omphalopleure). The sketch above shows trophoblast of the vascular yolk sac (troph) absorbing secretions from a uterine gland (gl ep). It is unclear whether there is exchange between the capillaries on the maternal (m cap) and fetal (foet cap) sides.
Bilaminar omphalopleure (non-vascular yolk sac) of Tasmanian bettongFrom Flynn Proc Linn Soc NSW 1930; 55: 506-531
Trophoblast of the non-vascular yolk sac (bilaminar omphalopleure) was implicated in the uptake of cellular material (cm) and red blood cells (haem). In current terminology (here) it is heterophagous.

Theodore Thomson Flynn (right) with his son the actor Errol Flynn
Theodore Thomson Flynn was a marine biologist and professor at the University of Tasmania. He named a fish Gibbonsia erroli after his son Errol Flynn the film actor.