Embryologists meet 1913 in Rio de Janeiro

From left: J. P. Hill, E. Bresslau and G. S. Sansom 1913

Instituto Oswaldo Cruz

J. P. Hill had made his name studying placentation in Australian marsupials. He returned to England in 1907 as Professor of Zoology at University College London. In October 1913, accompanied by G. S. Sansom he went to Brazil to obtain material from South American marsupials in particular the Brazilian common opossum (Didelphys aurita) (see biography here).

Whilst in Rio de Janeiro he met up with the eminent German zoologist Ernst Bresslau who was there from 1913 until the outbreak of war in the following year (see biography here). Bresslau was interested in the evolutionary origins of the mammary gland. Thus like Hill his research spanned monotremes, marsupials and eutherians. 

Bresslau was then at the University of Strasbourg. Later he was recruited to Cologne where he built up the zoology department. He was dismissed from this post by the Nazi regime in 1934 but went to start up zoology at the newly established University of Sao Paulo. Sadly he died there in the following year.

G. S. Sansom did interesting work on germ layer inversion in the water vole (Arvicola amphibius) and later with Hill on the guinea pig (Cavia porcellus). Sansom was a renowned climber. During World War I he served in the Royal Flying Corps and RAF and was awarded the Military Cross and Distinguished Flying Cross. 

Note on the photo: I have identified Hill and Bresslau by comparison with other photos. The printed text reads, "Prof. Ernest Bresslau - Strasborgo; Prof. J. P. Hill - Londres; Mr G. S. Sansom - Londres"

Aye-aye captain of its own raft

An aye-aye (Daubentonia madagascariensis) foraging
Joseph Wolf c. 1863 Wikipedia Commons (public domain)

We are used to molecular data shaping our view of evolution, so it is all the more delightful when a morphological study shakes the mammalian tree.  The pleasure is no less for it involving that strange Malagasy primate the aye-aye (Daubentonia madagascariensis).

It is widely accepted that Madagascar was colonized by mammals rafting across the Mozambique Strait (see previous post). The lemurs (Lemuriformes) and the aye-aye (within its own Infraorder Chiromyiformes) have hitherto been thought to be descended from a single founder.

New tree for strepsirrhine primates from Gunnel et al. 
Nature Communications 2018 (here) CC

Now a study in Nature Communications paves the way to a new scenario. The historical background is interesting. George Gaylord Simpson (a proponent of the rafting hypothesis) once proposed a new fossil species of strepsirrhine primate Propotto leakeyi from the early Miocene of Kenya. Subsequently this was reinterpreted as a fruit bat. Now Gunnell and co-authors have unearthed the specimens from the National Museums of Kenya and compared the morphology (especially the dentition) both to the aye-aye and to Plesiopithecus teras from a late Eocene site in Egypt.

Firstly, they show Simpson was right about Propotto. Secondly, they construct a tree (combining morphological and molecular data) showing the split between Lemuriformes and Chiromyiformes occurred in the Eocene. Thirdly, it is most parsimonious to assume two separate rafting events with the ancestor of the aye-aye drifting to Madagascar on its own raft. Finally, both rafting events are likely to have occurred in the Miocene, which explains the lack of fossils of earlier date.

Placentation in the aye-aye

Allantochorion of the aye-aye. From Hill & Burne 1922 (here)

Milne-Edwards briefly described the placenta of the aye-aye (C R Acad Sci 1884), but the first complete account is by Hill and Burne (here). They described the villous nature of the allantochorion and the presence of chorionic vesicles. This contributed to Hill's later characterisation of the "lemuroid stage" of placentation where the placenta is diffuse, non-deciduate and epitheliochorial (reviewed here).

Treasure houses under threat

The Field Museum Chicago
by Juanfibarra Wikimedia Commons CC BY 2.5

Museums house vast collections of specimens. For major museums of Natural History, these can be numbered in tens of millions. The specimens of greatest interest to embryologists will be in the wet collection and preserved as a rule in alcohol. Curating these specimens is an expensive business. When Chicago's Field Museum built a new Collections Resource Center the bill ran to $65 million and so stretched the budget that it resulted in cuts to museum staff (here).

Cross section through placental disc of a web-footed tenrec
(Limnogale mergulus) from Enders et al. (here). FMNH 165440

Now museum collections in the US are under further threat as the National Science Foundation has suspended its funding for the maintenance of biological research Collections (here). This is a matter of great concern.

Thanks to the Field Museum were able to describe the placenta from a rare specimen of an aquatic tenrec (above). We also used Field Museum specimens when reviewing the reproductive organs of bats (here).

Gravid uterus of a chimpanzee (Pan troglodytes) from the Hill Collection
currently housed at Museum für Naturkunde Berlin

Some museums house dedicated collections of embryological material. The J. P. Hill Collection is a good example and we have used it for several projects, including the first description of deep trophoblast invasion in a non-human primate (here).

The history of this collection is instructive. After Hill's death in 1954 it was stored in the attic of Dixon Boyd's house in Cambridge. It subsequently found what seemed to be a permanent home at the Hubrecht Laboratory in Utrecht. Together with the Hubrecht Collection it was eventually kept in a purpose built facility of a new building. With a change of director this space was seen as more suitable for -70 freezers and the future of the collection remained uncertain until it was removed to Berlin. The director subsequently became President of the Royal Netherlands Academy of Arts and Sciences!