Brain Cytoarchitecture in a Large Grazing Marsupial, Rufous Wallaby Thylogale billardieri.

1
Brain Cytoarchitecture in a Large Grazing
Marsupial, Rufous Wallaby Thylogale
billardieri. Cindy D. Knaff, under the direction
of Dr. John I. Johnson, Radiology
OLFACTORY SYSTEM
Results Visible lamination in cell groups within
the brain is one indicator of relatively well
developed systems. Sections from both species
show several visibly laminated brain regions
subserving olfaction, vision, and audition, as
well as a large extent of laminated cerebral
isocortex.
RUFOUS WALLABY Thylogale billardieri
DOMESTIC SHEEP Ovis aries
turs
The OLFACTORY BULBS in both species are large and
show a high degree of visible lamination.
From http//brainmuseum.org/Specimens/marsupalia/r
ufwallaby/index.html
Original photograph, John I. Johnson
ABOVE Coronal view of the olfactory bulb and
stalk..
ABOVE Coronal view of the olfactory bulb and
stalk.
The VISUAL SUPERIOR COLLICULI are larger than the
AUDITORY INFERIOR COLLICULI in both species, and
show visible lamination. This is typical of
herbivorous prey species who must keep a watch
for predators while still far away.
VISUAL AND AUDITORY SYSTEMS

The VISUAL LATERAL GENICULATE NUCLEUS shows
visible lamination in both species. Sheep have
three distinct laminae in each lateral geniculate
nucleus (Clarke, et al., 1988), while Rufous
Wallabies have 7 or 8 laminae (Sanderson et al.,
1984, 1987), some of which are visible here.
ABOVE Sagittal view of the superior and inferior
colliculi.
ABOVE Sagittal view of the superior and inferior
colliculi.
VISUAL SYSTEM
kog

ABOVE Six standard views of the intact brains.
From http//brainmuseum.org/Specimens/marsupalia/r
ufwallaby/index.html
From http//brainmuseum.org/Specimens/artiodactyla
/sheep/index.html
The AUDITORY DORSAL COCHLEAR NUCLEUS shows
distinct lamination in both species. This nucleus
has recently been shown to have a cerebellum-like
function (Oertel Young, 2004).
Introduction Brain evolution can be seen through
comparative neurology. Wallabies, large grazing
marsupials, provide opportunities to study
evolutionary convergences with brains of
independently evolved brains of large grazing
placental mammals, from a separate branch of
mammalian radiation. We have analyzed the
internal structure of the brains of Rufous
Wallabies Thylogale billardieri, in direct
comparison with their counterpart structures in
Domestic Sheep Ovis aries.
ABOVE Sagittal view of the lateral geniculate
nucleus and optic tract.
ABOVE Sagittal view of the lateral geniculate
nucleus and optic tract


AUDITORY SYSTEM

Conclusions These particular parallel
hyperdevelopments in maximally distant related
species appear to be related to environmental
adaptations rather than to phylogenetic
relationships.
Procedures Sections of brains from museum
collections were examined for evidence of
specializations related to herbivorous grazing
behavior. These wallaby and sheep brains were
dehydrated, embedded in nitrocellulose
(celloidin), sectioned at 35 um intervals and
were stained with thionine, a standard Nissl
staining procedure, to show distributions of
neuronal cell bodies..
REFERENCES
Clark PG, Martin KA, Rao Vm, Whitteridge D. The
dorsal lateral geniculate nucleus of the sheep
and its retinal connections. Q J Exp Physiol.
1988 May73(3)295-304. Oertel D. Young ED,
Whats a cerebellar circuit doing in the auditory
system? Trends Neurosci. 2004 Feb27(2)104-10. S
anderson KJ, Haight JR, Pettigrew JD. The dorsal
lateral geniculate nucleus of macropodid
marsupials cytoarchitecture and retinal
projections. J Comp Neurol. 1984 Mar
20224(1)85-106. Sanderson KJ, Nelson JE,
Crewther DP, Crewther SG, Hammond VE.
Retinogeniculate patterns in diprotodont
marsupials. Brain Behav Evol. 198730(1-2)22-42
ABOVE Horizontal view of the dorsal and ventral
cochlear nuclei.
ABOVE Horizontal view of the dorsal and ventral
cochlear nuclei.
See the atlases of the brains of dolphins, sheep,
humans and axolotls at http//www.brains.rad.msu.e
du, http//brainmuseum.org or http//www.
user/brains/atlases msu.edu A similar atlas of
the brains of rufous wallabies is in preparation
for these sites.
Supported by The Division of Integrative Biology
and Neuroscience of THE NATIONAL SCIENCE
FOUNDATION grants IBN 0131267, 0131028, 0131826.
Poster design, adviser and printer Gearl Diggs,
Radiology Dept. Michigan State University