At only a few inches long and with no distinguishing external physical features to speak of, Scutisorex
somereni, better known as the Hero or Armoured Shrew, is seemingly an unremarkable creature.
That is, until you accidentally step on one.
You see, the Hero shrew can comfortably survive being stood on by a typical adult human without
any injury.
The secret to this remarkably skill lies in the shrew's skeletal system, or more specifically,
its spine.
Unlike almost every other mammal on Earth, with one notable exception which we'll get
to in a moment, the Hero shrew's spine features intricate interlocking vertebrae, a very large
number of spinal processes, and is incredibly thick relative to its size, accounting for
roughly 4% of its total body weight, or about a 6-8 times higher percentage than mammals
of comparable size.
As a final insult to other, lesser shrews, the Hero shrew's spine also contains more
than twice as many lumbar vertebrae (10-11 instead of 5) giving the little guy significantly
more flexibility than its peers, allowing the Hero shrew to turn around in much tighter
quarters than its brethren can.
What makes this adaptation even more unusual is that most of the rest of the Hero shrew's
skeleton, aside from slightly beefier ribs, doesn't follow suit and is not all that different
to that of other small mammals.
However, as alluded to previously, in some of the earliest reports of encounters with
this creature in its native habitat of the forests of certain regions of Africa, researchers,
such as German naturalist Herbert Lang, noted that
“Whenever [the Mangbetu] have a chance, they take great delight in showing to the
easily fascinated crowd its extraordinary resistance to weight and pressure.
After the usual hubbub of various invocations, a full-grown man weighing some 160 pounds
(72 kg) steps barefooted upon the shrew.
Steadily trying to balance himself upon one leg, he continues to vociferate several minutes.
The poor creature seems certainly to be doomed.
But as soon as his tormentor jumps off, the shrew, after a few shivering movements, tries
to escape, none the worse for this mad experience and apparently in no need of the wild applause
and exhortations from the throng.”
For reference, the man in this story weighed around 1,000 times more than a typical Hero
shrew.
This would be like having a Boeing 757 balanced on top of a typical adult male, if humans
could perform the same feat, scaled up.
Although the Mangbetu have known about the Hero shrew's remarkable resilience to pressure
for centuries, when British zoologist, Oldfield Thomas became the first western expert to
encounter one back in 1910, he didn't notice that there was anything unusual about it.
In fact, Oldfield described the creature as being rather uninteresting, only noting that
it was slightly larger than an average shrew and had quite dense fur.
The shrew's remarkable spine wasn't observed by academics for another seven years, when
a curator at the Natural History Museum stumbled across a preserved specimen and wrote a paper
about it called, "The skeletal characters of Scutisorex Thomas".
Since its discovery until very recently, experts were baffled about exactly why the Hero shrew
evolved in the way that it did, with there being no obvious explanation for why its spine
needs (or needed) to be as strong as it is.
There was also more or less a "missing link" between the spines of a typical shrew and
the exceptionally different spine of the Hero shrew.
This latter point was initially explained by perhaps being an example of punctuated
equilibrium, a theory that posits that under just the right circumstances, a subset of
some members of a species can evolve rapidly in response to a threat or change in environment
while the rest of the species that aren't experiencing these same environmental pressures
may stay more or less the same.
Once the rapidly evolving group adapts to the environmental pressures, it also more
or less stays the same in this new form, with the rapid scale and isolation of the event
leaving little record of the transition.
However, quite recently the potential "missing link" was found.
In 2012, William Stanley and his team, acting on behalf of the Field Museum of Natural History
in Chicago, encountered a close relative of this remarkable shrew species in a small African
village in the Democratic Republic of Congo.
Like the Hero shrew, this new species, named the Scutisorex thori, sported an unusually
thick spine consisting of interlocking vertebrae.
Unlike the Hero shrew, though, this new species had only 8 lumbar vertebrate, 3 more than
regular shrews, but 3 less than the Hero shrew.
It also had fewer and bigger spinal processes, a little more like a typical mammalian spine.
Essentially, this spine is more or less half way between a Hero shrew's and a typical shrew
in form.
After analysing the new species of shrew's DNA, the researchers found that, indeed, they
are closely related to the Hero shrew.
As to the question of why such an evolution would have taken place, during his time in
the Congo, Stanley was told by locals that the best place to find Hero shrews was in
swampy palm forests, where beetle larvae and other such creatures can often be found under
dead palm leaves, branches, and the like.
After watching the natives pry up such things to expose large grubs for harvesting, he logically
hypothesized that the reason this new shrew, and by extension its sister species, had evolved
such strong backs and spinal muscles (as well as thicker ribs) was because it allowed them
to pry up branches and other such objects enough to expose the grubs the shrew like
to eat, all without risking injury.
This gives these shrews a significant biological advantage over other shrews in certain regions.
However, according to Stanley "no one has seen the shrew actually do this", so it remains
just a very reasonable sounding theory without hard evidence to back it up.
Bonus Fact: If you thought the Hero shrew was impressive,
let us now introduce you to a creature able to survive being boiled in water, frozen to
just 1 degree above absolute zero, survive atmospheric pressure equivalent to about six
times the pressure at the deepest part of the ocean, or on the flipside a complete lack
of atmospheric pressure in space.
They can also survive near total dehydration, and exposure to massive amounts of ionizing
radiation.
On top of that, they can also go dormant and live for as much as a century in this state,
just waiting for a drop of water to rejuvenated them.
What mighty creature is this?
It turns out one that would make Ant-man look giant, as the “water bear” or more aptly
“tardigrades” (from the Latin "tardigradus" meaning ‘slow walker’) are only about
the size of a grain of sand.
There are over 1000 known species of Water Bears (called such because when they walk,
their gait loosely resembles plump little bears ambling along on eight legs), these
creatures thrive in the most extreme environments on every corner of the Earth- from the Equator
to the Polar regions- forests, swamps, deserts, tundras, mountains, glaciers, hot springs-
from the highest point on Earth along the Himalayan mountain range, to the deepest parts
of the sea, tardigrades are there.
Less excitingly, they can also be found in your backyard where you can usually find them
in common moss, lichens and ferns, feeding on natural detritus in the undergrowth.
In fact, if you own a microscope, you can observe tardigrade behavior up close and personal
via just finding a piece of moss and soaking it in some spring water in a petri dish and
then taking a look.
Although the scientific community has long known about tardigrades (since 1773), it is
still somewhat of a mystery how they manage the amazing feat of cryptobiosis, that is,
the ability to almost completely halt their metabolic processes, losing up to 97%-99%
of their total moisture.
When they then encounter water again, they reanimate, with the current record being 120
years to reanimation (though that particular creature simply moved a little and then died
when reanimated.
But when we go to spans such as a decade or two, most tardigrades are able to fully reanimate
with no problem.)
For reference, the natural life span of the tardigrade is just about a year, unless they
are dehydrated.
One of the keys to this hardy creature’s success seems to be the presence of a cellular
sugar called trehalose which preserves the membranes that form their bodies.
Although hardly the answer to human suspended animation, scientists are looking at trehalose
as a viable way to preserve human eggs during freezing for later fertilization.
In any event, when tardigrades dry up, they become “tuns”, little capsules that are
easily transported and dispersed over the Earth via the wind, the oceans, or in an animal’s
gut.
(Yes, they can sometimes survive there too.)
Not remarkable enough for you?
Tardigrades can also survive as high as 5,000 grays or 500,000 rads of ionizing radiation,
though above 100,000 rads does seem to make them sterile.
For reference, humans die around a "mere" 1,000-2,000 rads and will suffer significant
damage with much less.
In order to test some of the tardigrade's amazing abilities, in 2007, the European Space
Agency launched the FOTON-M3 spacecraft hurtling a capsule full of science experiments into
the heavens.
Its subjects included live tardigrades, who returned from space after orbiting Earth for
12 days, all the while being subjected to the near vacuum of space and the full spectra
of deadly solar and cosmic radiation.
How did the Water Bears hold up?
No problem for a large percentage of them.
About 68% of them were just fine and kept on amblin’ once back on Earth.
For reference, besides surviving the near vacuum of space, some species of tardigrade
can also withstand up to 6,000 times atmospheric pressure at sea level.
As noted at the beginning of this Bonus Fact, this is about 6 times more pressure than at
the deepest point in the ocean.
I, for one, welcome our new tardigrade overlords.