By Mindy Weisberger, Senior
Writer | October 23, 2017 01:40pm ET
In creatures with backbones, skulls
get progressively bigger as the animal grows to maturity, but then tend to stay
the same size thereafter. However, something happens to the skulls of adult
red-toothed shrews that is exceedingly rare among vertebrates: The animals'
heads shrink and expand in synch with seasonal changes.
For the first time, a team of
researchers has documented the complete cycle of these dramatic changes in
living Sorex araneus shrews, describing their findings in a new study
published online today (Oct. 23) in the journal Current
Biology.
The researchers captured X-ray
images that recorded the shrunken and recovered states of the shrews' skulls
and brains, finding that the animals' heads contracted by up to 20 percent in
preparation for winter and ballooned back to their previous size over the
spring and summer. [The
World's 6 Smallest Mammals]
This shift in skull size— known
as the Dehnel effect — was previously documented in studies of the skulls
removed from deceased shrews. But this is the first evidence to track this
remarkable adaptation in living animals over time and link it to other
biological changes, the study authors reported.
For the new investigation,
scientists captured 12 wild red-toothed
shrews, so named because of a reddish tint in their front teeth caused
by iron deposits in the enamel, according to a study published in 2006 in
the Journal
of Mammalogy.
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