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A manatee can move each side of its lip pads
independently. This flexibility allows the manatee to "grab"
aquatic plants and draw them into its mouth.
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Manatees do not
have eyelashes, their eye muscles close in a circular motion,
much like an aperture on a camera.
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They have a lid-like membrane
(called a nictitating membrane) that closes over their eyes for
protection when they are under water.
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Manatees can hear very
well despite the absence of external ear lobes.
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A manatee's
heart beats at a rate of 50 to 60 beats a minute. The heart rate
slows down to 30 beats a minute during a long dive.
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Manatees
have no "biting" teeth, only "grinding" teeth.
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A manatee's teeth
(all molars) are constantly being replaced. New teeth come in at
the back of the jaw and move forward about a centimeter a month.
The front molars eventually fall out and are replaced by the
teeth behind them.
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Manatees have only six cervical (neck)
vertebrae. Most all other mammals, including giraffes, have
seven. As a result, manatees cannot turn their heads sideways,
they must turn their whole body around to look behind them.
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The
manatee's rib bones are solid, there is no marrow. They make red
blood cells in their sternum where marrow is found.
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The manatee
has pelvic bones, but they are not attached to its skeletal
frame, they are remnants of the time manatees lived on land. The
bones are found in a cartilage tissue area of the body in the
vicinity of the reproductive organs and the urinary bladder. The
bones are soft when the manatee is young and later harden as
they mature.
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Other remnant bones found in the manatee are the
hyoid bones located near the neck region. These bones are
similar to the Adam's apple in humans. Today, there is no known
use of these bones in the manatee.
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The manatee's lungs lie along
its backbone instead of along its rib cage as is found in most
mammals. Besides breathing, the lungs help the manatee with
buoyancy control.
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The bones in a manatee's flipper are similar
to a human hand. The jointed "finger bones" of the flipper help
the manatee move through the water, bring food to its mouth, and
hold objects.
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Three or four nails are found at the end of each
flipper.
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The adult manatee averages about 10 feet long and
weighs about 1000 pounds.
