12S - Extremely Interesting Animal Facts

BIOLOGY
Extremely Interesting Animal Facts
The Exciting Physiologies of Different Animals
SARA REMSEN
E
ver since I was young, I have been
collecting fun facts about animals.
By the time I was ten, I could name
more than 200 mammals off the top of
my head at the dinner table. Although
my parents raised their eyebrows at me,
they supported my voracious curiosity.
They gave me Marine Mammal Biology for
Christmas and The Illustrated Veterinary
Guide for my birthday. I absorbed all the
animal facts I could find and quoted them
back to my surprised parents, finding some
particularly interesting ones. Although
we like to think the human species is the
pinnacle of evolutionary success, I want to
share some extraordinary facts that remind
us of the many animal species whose
abilities far exceed our own.
Sea Dragons: Creatures You
Never Imagined
I like to believe that I knew about sea
dragons before anyone else. In sixth grade,
I chose to write my marine biology report
on these understudied creatures when my
classmates were writing reports on starfish
and dolphins. Relatives of sea horses and
pipefish, sea dragons are members of
the Syngnathidae family that live in the
waters off the coast of Perth, Australia.
There are two species, weedy and leafy,
named for their habitat and corresponding
camouflage.
Sea dragons have long snouts and bony
rings around their bodies, with leafy or
weedy appendages. Their small, transparent
dorsal and pectoral fins can propel them in
the water, but sea dragons spend most of
their time drifting in patches of seaweed.
Sea dragons survive on a diet of Mysid
shrimp and amphipods (6, 10). Like male
seahorses, male sea dragons are responsible
for child rearing. When a male sea dragon
is ready to mate, his tail turns bright yellow,
and the female deposits bright pink eggs
onto the brood patch on the underside of
his tail. The male carries the eggs for about
four to six weeks, at which point he releases
the fully–formed baby sea dragons.
The Wolverine Newt
Imagine you are a newt: you have the
short stubby legs of a primitive amphibian
and it is impossible to outrun a predator.
Most salamanders and newts have avoided
extinction by either hiding or advertising
their toxicity through bright warning
colors.
The Spanish ribbed newt takes an
entirely different approach to survival.
When confronted with a predator, it sticks
its pointed ribs outward through its skin,
exposing poison barbs (9). First noticed by
a natural historian in 1879, this salamander
was the subject of recent research that
revealed that the defense comes in two
parts. When the newt is threatened, it
Image courtesy of Derek Ramsey retrieved from http:/ / en.w ikipedia.org/ w iki/ File:Leafy_Seadragon_Phycodurus_eques_2500px_PLW_edit.jpg (accessed 10 M ay 2012)
Figure 1: A leafy sea dragon in the kelp forests off the coast of Perth, Australia.
26
Image courtesy of Richard Ling retrieved from http:/ / en.w ikipedia.org/ w iki/
File:Phyllopteryx_taeniolatus1.jpg (accessed 10 M ay 2012)
Figure 2: The relative of the leafy sea dragon, the
weedy sea dragon.
secretes a noxious substance on its skin
and then contorts its body to force the
sharp tips of its ribs through its skin. The
ribs become fierce, poison–tipped barbs,
deterring attackers. These spear–like ribs
must break through the newt’s body wall
every time it evokes the defense. However,
as is characteristic of many amphibians, the
Spanish ribbed newt posses rapid tissue
regeneration characteristics that allow it to
recover from its puncture wounds (9)
Antifreeze Blood
Fish are ectotherms: the external
environment determines their internal body
temperature. This form of thermoregulation
means that fish are the same temperature as
the rivers and oceans they inhabit—even
when the water is below freezing. Antarctic
Notothenoids are fish that inhabit the frigid
waters of the Antarctic, where temperatures
are constantly below 0 degrees Celsius. In
order to keep ice crystals from forming
in their blood, fish from the suborder of
Notothenioidei have unique antifreeze
proteins in their circulatory system.
Unlike commercial antifreezes, these
glycoproteins do not lower the freezing
point of water. Instead, Notothenioids’
antifreeze glycoproteins (AFGPs) bind to
ice crystals as soon as they form, blocking
other water molecules from binding and
thereby preventing the development of a
larger crystal. There are several structural
varieties of AFGPs that have convergently
evolved in several families of cold–dwelling
fish. Recent research suggests that these
DARTMOUTH UNDERGRADUATE JOURNAL OF SCIENCE
Image courtesy of Uw e kils retrieved from http:/ / en.w ikipedia.org/ w iki/ File:Icefishuk.jpg
(accessed 10 M ay 2012)
Figure 3: An icefish off the coast of Antarctica.
proteins evolved from mutations in
pancreatic trypsinogens and adapted for
survival in frigid water (5).
Eat a Bedtime Snack or You’ll
Die
Hummingbirds are one of the only
species of birds capable of hovering because
of their complex, figure eight wing patterns.
However, this agility comes at the cost of a
metabolism which demands a near constant
supply of nectar. The aerial performance
of hummingbirds’ approaches the upper
bounds of oxygen consumption and muscle
power input for all vertebrates (4). While
nectar is popularly perceived as the food of
choice for hummingbirds, insects actually
provide the primary source of nutrition.
Fasting becomes a problem at night,
when hummingbirds need to sleep. In
order to survive the night without starving
to death, hummingbirds enter a state
called torpor (8). When hummingbirds
enter torpor, their body temperature
drops and their metabolism slows. A cold
hummingbird body has lower energy
needs than a warm, flying one and burns
fewer calories. Because hummingbirds
cannot both sleep and eat at the same
time, entering torpor at night enables
hummingbirds to survive until their next
meal in the morning.
Image courtesy of Derek Ramsey retrieved from http:/ / en.w ikipedia.org/ w iki/ File:Leafy_
Seadragon_Phycodurus_eques_2500px_PLW_edit.jpg (accessed 10 M ay 2012)
Figure 6: Hummingbirds must constantly forage
for nectar and insects throughout the day to
maintain their high metabolism.
SPRING 2012
Image courtesy of Peter Halasz retrieved from http:/ / en.w ikipedia.org/ w iki/ File:Pleorodeles_w altl_crop.jpg (accessed 10 M ay 2012)
Figure 4: The Spanish ribbed newt possesses sharp ribs that can puncture through its skin as a defense
mechanism, exposing poisonous barbs to predators.
Mammals vs. Reptiles:
Locomotion and Respiration
Reptiles and amphibians still retain
the ancient form of locomotion practiced
by our fishy ancestors: lateral undulation.
Reptiles swing opposite pairs of their legs
forward, with their legs scrunching at their
side as they move. Unfortunately for these
reptiles, the muscles that control their legs
also control their lungs (3). As reptiles flex
sideways, they compress a lung shunting
air between their two lungs, rather than
expelling old air and inhaling fresh air.
As a result, lizards must always travel in a
run-stop-run pattern.
Mammals, unlike reptiles, have
diaphragms. The diaphragm is a muscle
that contracts to create a vacuum inside
the chest cavity thereby causing the lungs
to expand. Because the diaphragm is
independent of the muscles that power
locomotion in mammals, we are able to
breathe and run at the same time. High
breathing rates enable a greater oxygen
intake and stronger, more frequent muscle
contractions. Perhaps the diaphragm
is a strong component of mammals’
evolutionary success; if migration was
quick and easy, our rodent-like, primitive
ancestors could travel more easily to find
new resources.
Colors We Can’t See:
In our eyes, we have two types of
cells called rods and cones that send light
information to our brain. Rods are the most
sensitive to stimulation than cones and
are found mostly at the edge of the retina,
where they contribute to the motion–
sensitivity of our peripheral vision. Cones
give our world color. There are different
types of cones, with each type containing
a pigment that is sensitive to a particular
wavelength of light. In humans, there are
three types of cones: red, green, and blue.
These are the same RGB colors of the
LEDs in lampposts, stoplights, and streets
signs that mix to produce the spectrum
of colors we are familiar with. Humans are
Image courtesy of Bjorn Christian Torrissen retrieved from http:/ / en.w ikipedia.org/ w iki/
File:Reindeer-on-the-rocks.jpg (accessed 10 M ay 2012)
Figure 5: Caribou can migrate huge distances
between patches of forage on the tundra, in part
because it is so easy for them to breathe and move
at the same time.
27
References
Image courtesy of Paul Hirst retrieved from http:/ / en.w ikipedia.org/ w iki/ File:Anole_Lizard_Hilo_Haw aii_edit.jpg (accessed 10 M ay 2012)
Figure 7: An anole perches on a branch to catch its breath.
thus classified as trichromads (7). When
one of these cones is non-functioning, it
causes vision distortions, such as red–green
colorblindness.
Birds are tetrachromads: they have
an extra type of cone and can see into the
ultraviolet (UV) spectrum (7, 1). Most
dinosaurs had four cones, but mammals
lost two of these cones when they became
nocturnal and had little use for color
vision. When mammals diversified in their
later evolution, some regained a different
third cone to see into green wavelengths to
complete our RGB set (7). Others did not
and remained dichromads. Birds, however,
being phylogenetically close to dinosaurs
retained their four cones which are sensitive
to UV wavelengths.
Birds have another jump on mammals:
specialized oil droplets in birds’ cones
28
narrow the spectral sensitivity of the
pigments, enabling birds to distinguish
more colors than with pigments alone (7).
Recent studies suggest that bird plumage is
even more colorful than we can imagine (1,
2).
The more I learn about animal
adaptations and evolution, the more
the complexity of the world amazes me.
Although I envy the naturalists of the 1800s
who stepped on a new species in their
backyard and went on to publish hundreds
of papers about their findings, I know
science is far from complete and much has
yet to be discovered.
1. A. T. D. Bennett, I. C. Cuthill, Vision Res. 34(11),
1471-8 (1994).
2. D. Burkhardt, E. Finger, Naturwissenschaften 78(6),
279-80 (1991).
3. D. R. Carrier, Paleobiology 13: 326–341 (1987).
4. P. Chai, R. Dudley, Nature 377, 722-25 (1995).
5. L. Chen, A. L. DeVries, C. C. Cheng, PNAS 94(8),
3811-3816 (1997).
6. R. M. Connolly, A. J. Melville, J. K. Keesing, Marine
and Freshwater Research 53, 777–780 (2002).
7. T. A. Goldsmith, M. C. Stoddard, R. O. Prum,
Scientific American 68-75. (2006).
8. O. P. Pearson, The Condor, 52(4),145-152 (1950).
9. M. Walker, Bizarre newt uses ribs as weapons (21
August 2009). BBC News (16 March 2011).
10. N. G. Wilson, G. W. Rouse, Zool. Scr. 39(6), 551-8
(2010).
CONTACT SARA REMSEN AT 3!2!%2%-3%. $!24-/54(%$5
DARTMOUTH UNDERGRADUATE JOURNAL OF SCIENCE