That Shell isn't What it Seems
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Chelonians' shells look a little like human body armor, so one might conclude that
they're reptilian versions of the powered exoskeleton that makes Iron Man such a
fearsome superhero. But the shell, which is made up of about 50 different bones,
actually is an evolutionary modification of the rib cage and part of the vertebral
column. And contrary to what you may have seen in animated cartoons, a
chelonian can't take off its shell and crawl out of it -- just as you couldn't
dismantle your own spine and ribs, according to the University of Michigan
Museum of Zoology.
The shell itself actually has two parts: an upper section, the carapace, and a
lower portion called the pastron, which are joined by a bony bridge. Some turtles
have a moveable joint, usually in the plastron, that acts as a hinge and enables
the creature to pull the two shell sections together tightly while it retracts its body
inside. Shells have nerves embedded in them and a blood supply as well, so if a
chelonian's shell is injured, it may bleed and feel pain.
Tortoises Orbited the Moon Before Astronauts Did
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In September 1968, the Soviet Union launched the space probe Zond 5 on a
mission to orbit the moon and test conditions as a prelude to a possible lunar
mission by cosmonauts. In addition to a life-size human mannequin equipped
with radiation detectors, the spacecraft carried a number of living passengers,
including a pair of Russian tortoises that newspaper reports initially described as
"turtles." After a week in space, Zond 5 returned to Earth and, despite a failure of
crucial altitude detectors, successfully splashed down in the Indian Ocean.
Along with the other creatures, the tortoises were rescued and brought back to
the Soviet Union for study. The Soviets revealed that the tortoises had lost about
10 percent of their body weight, and showed an "excessive content" of glycogen
and iron in their liver tissue and some changes in their spleens. Otherwise,
though, the tortoises remained active and showed no loss of appetite, according
to NASA.
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One of the most fearsome Chelonians around is the alligator snapping
turtle, Macroclemys temminckii, which is the biggest freshwater turtle in North
America. It can grow to 2.5 feet long, can weigh as much as 200 pounds, and
has powerful jaws, a sharply-hooked beak, nasty bearlike claws and a muscular
tail. The alligator snapping turtle does eat some aquatic plants, but it's mostly a
carnivore that dines on a variety of smaller creatures -- fish, frogs, snakes,
worms, clams, crayfish and even other turtles.
The alligator snapping turtle catches prey by way of a fiendishly clever
evolutionary adaptation: an appendage to its tongue that, when wriggled, looks
an awful lot like a worm, according to the Saint Louis Zoo. A fish who gets fooled
by the turtle's tongue will swim right into range of the hungry predator's jaws.
They Make Sounds, Even Though They Lack Vocal Cords
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Chelonians can make sounds by swallowing or by forcing air out of their lungs,
and some species emit unique noises. The red-footed tortoise (Chelonoidis
carbonaria), a South American species, makes a series of clucks that sound like
a chicken. Male Travancore tortoises (Indotestudo forstenii) in Southeast Asia
emit a high-pitched whine that sounds like an electric motor when they're seeking
mates. The giant musk turtle (Staurotypus salvinii), which is found in Central
America, is known for yelping like a dog when it's startled or being attacked.
But the weirdest sound is made by nesting female leatherback sea turtles
(Dermochelys coriacea), who make a distinctly unladylike noise that resembles a
human belching, according to the book Turtles: An Extraordinary Natural History
245 Years in the Making.
Males Select Potential Mates By Sniffing Tails
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OK -- so humans shouldn't really talk, since we have some pretty silly mating
behavior of our own, including selecting potential partners on the basis of their
dancing ability or zodiac sign. In comparison, perhaps male chelonians' method
of sniffing under other female chelonians' tails is relatively sensible, not to
mention functional.
Since both males and females' sexual organs are hidden inside their cloaca, a
cavity used for both reproduction and eliminating waste, humans have trouble
telling by sight which shelled creature is female and which is male. Turtles and
tortoises, however, possess an extremely keen sense of smell. According
to Turtles: An Extraordinary Natural History 245 Years in the Making, males
apparently can detect the scent of pheromones, a type of identifying chemical,
that is secreted inside a female's cloaca. Chelonians rely on scent so heavily that
a male red-footed tortoise once was observed trying to mount a head of lettuce
that a female had just climbed over, according to the book Behavior of Exotic
Pets.
They Don't Have Ears, But Can Perceive Low-Pitched Sounds
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You may have heard that turtles and tortoises, which lack an ear opening, are
deaf, but that's not completely accurate. It's true that chelonians can't hear
anywhere near as well as humans and many other species can. But they can
detect certain types of sounds. Scientists who've used light microscopes to study
the ear structure of marine turtles, for example, have found that their middle ears
have a very thick eardrum-like membrane, which limits the frequency range they
can perceive. But that adaptation is extremely efficient for bone conduction
hearing at low frequencies, according to Behavior of Exotic Pets.
According to reptile expert Melissa Kaplan, Chelonians generally can perceive
sounds in the 50 to 1,500 Hz range, compared to the typical human hearing
range of 20 to 20,000 Hz. Our hard-shelled friends also can't differentiate
loudness as well as we can. The spotted turtle (Clemmys guttata), for example,
has a peak sensitivity of just 4 dB, compared to 120 dB in humans. The upshot is
that while turtles and tortoises may not be able to appreciate, say, the nuances of
Mahler's "Symphony No. 2," their sense of hearing is good enough to detect the
presence of predators.
Turtles Are Nearly As Old As The Dinosaurs
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Chelonians and dinosaurs emerged and developed at pretty much the same
time, in natural history terms. The oldest known fossil turtle, Odontochylys
semitstacea, dates back 220 million years, which means it showed up 23 million
years after the earliest known dinosaur relative, Asilisaurus kongwe. That longextinct ancient turtle had a partial shell covering its belly, but it didn't extend to
completely protect its back, like the ones that modern chelonians have, according
to National Geographic.
Amazingly, some turtles that existed in the age of the dinosaurs are still around.
Pelomedusidae, a family of freshwater turtles native to eastern and southern
Africa, first appeared about 120 million years ago. The first tortoises emerged on
land at the start of the Tertiary Period 65 million years ago, shortly after the
dinosaurs died out in a mass extinction. In the ocean, the oldest surviving
species of sea turtles, the Cheloniidae, date back 55 million years, according to
the book Turtles of the World.
Turtles Breathe Without A Diaphragm
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Most air-breathing vertebrates draw air in and out of their lungs using a
diaphragm, which is a muscle that contracts and relaxes with each breath to
expand the ribs. It's pretty easy to tell when one's breathing because its body
moves. But turtles don't have a diaphragm, which is all well and good, since the
rigidity of their shells would prevent their ribs, which are connected to them, from
expanding. Instead, turtles must move their limbs or neck, and utilize other
muscles connected to the pleural cavity (the area around the lungs), to help them
breathe.
Some turtles also have special muscles situated between their limbs and lungs to
aid in breathing, or they have an additional breathing-related trick that allows
them to remain underwater for longer periods. According to the book Turtles: An
Extraordinary Natural History 245 Years in the Making, some turtles use
buccopharyngeal breathing, in which they take water into their mouths and then
pass it out of their nostrils. Along the way, the oxygenated water passes along
the capillary-rich tissue inside their necks, allowing additional oxygen to enter
directly into the bloodstream.
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Like us, our shell-wearing reptilians are visually oriented creatures. They rely on
sight to identify other members of the same species, food, and potential danger,
such as predators. Sea turtles, for example, are so dependent on sight that when
researchers blindfolded some of them, the animals were unable to find their way
back into the water.
Research also shows that turtles not only can perceive colors, but that certain
colors -- red, orange and yellow -- seem to be the most appetizing to them. When
they see an object in one of those shades, they display "investigative behavior,"
which suggests that they're checking it out to see if they want to eat it, according
to Turtles: An Extraordinary Natural History 245 Years in the Making.
There's A Turtle That Seems Part Skunk
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The African helmeted turtle, Pelomedusa subrufa, is the most widespread turtle
species in Africa. It's found just about everywhere south of the Sahara desert. It's
a hunter-scavenger that hunts in packs and seems happy to eat most anything,
from parasites lodged in the skin of rhinoceroses to young birds and small
mammals, according to Turtles of the World. It attacks ducklings by dragging
them underwater, and steals bait from anglers' hooks, habits which make it
disliked by many Africans.
But the helmeted turtle's reputation is not just odious, but odorous as well. It
smells really, really awful. That aroma comes from four glands, one under each
leg, which release a foul-smelling liquid seems to repulse horses as well as
humans, according to the International Wildlife Encyclopedia. Despite that
unpleasant odor, villagers sometimes dig up the turtles from their mud nests
during wet season for food. However, the smelly shelled creatures don't have
enough meat on them to make a very satisfying meal, according to Turtles of the
World.
From: http://www.animalplanet.com/tv-shows/call-of-the-wildman/lists/10-weird-turtle-facts/