10.6084/m9.figshare.4588471.v2
Dos Santos S.E.
Dos Santos
S.E.
Porfirio J.
Porfirio
J.
da Cunha F.B.
da Cunha F.B.
Manger P.R.
Manger
P.R.
Tavares W.
Tavares
W.
Pessoa L.
Pessoa
L.
Raghanti M.A.
Raghanti
M.A.
Sherwood C.C.
Sherwood
C.C.
Herculano-Houzel S.
Herculano-Houzel
S.
Supplementary Material for: Cellular Scaling Rules for the Brains of Marsupials: Not as “Primitive” as Expected
Karger Publishers
2017
Evolution
Allometry
Marsupials
Brain size
Numbers of neurons
Glia/neuron ratio
Cortical expansion
2017-07-25 14:55:32
Journal contribution
https://karger.figshare.com/articles/journal_contribution/Supplementary_Material_for_Cellular_Scaling_Rules_for_the_Brains_of_Marsupials_Not_as_Primitive_as_Expected/4588471
<p>In the effort to understand the evolution of mammalian brains, we
have found that common relationships between brain structure mass and
numbers of nonneuronal (glial and vascular) cells apply across eutherian
mammals, but brain structure mass scales differently with numbers of
neurons across structures and across primate and nonprimate clades. This
suggests that the ancestral scaling rules for mammalian brains are
those shared by extant nonprimate eutherians - but do these scaling
relationships apply to marsupials, a sister group to eutherians that
diverged early in mammalian evolution? Here we examine the cellular
composition of the brains of 10 species of marsupials. We show that
brain structure mass scales with numbers of nonneuronal cells, and
numbers of cerebellar neurons scale with numbers of cerebral cortical
neurons, comparable to what we have found in eutherians. These shared
scaling relationships are therefore indicative of mechanisms that have
been conserved since the first therians. In contrast, while marsupials
share with nonprimate eutherians the scaling of cerebral cortex mass
with number of neurons, their cerebella have more neurons than
nonprimate eutherian cerebella of a similar mass, and their rest of
brain has fewer neurons than eutherian structures of a similar mass.
Moreover, Australasian marsupials exhibit ratios of neurons in the
cerebral cortex and cerebellum over the rest of the brain, comparable to
artiodactyls and primates. Our results suggest that Australasian
marsupials have diverged from the ancestral Theria neuronal scaling
rules, and support the suggestion that the scaling of average neuronal
cell size with increasing numbers of neurons varies in evolution
independently of the allocation of neurons across structures.</p>