Adaptations: The Head
In many ways,
a Manatee looks at, listens to, tastes, smells, and chews the world through
its head. Many features of a Manatee's head show unique adapations.
As you can see, manatees have small eyes. But despite the small
size they can see very well. Do manatees have eyelashes? No, manatees
have a protective covering called a nicitating membrane which can cover
the eye to protect it.
Facial whiskers on the manatee's head give it another sensory
tool. Called "vibrissae", these facial whiskers may be as
sensitive as our fingers. In fact, scientists at Mote
Marine Lab have
trained manatees to choose between two targets using only the vibrissae.
How? The manatees are blindfolded and then they touch two targets that
have different width grooves or ridges with their whiskers--and they
can tell the difference between the two!
have very unique lips that help them gather, grasp and manipulate food.
Since manatees don't have hands, their prehensile lips are very important,
helping the manatee eat almost like the elephant's trunk helps it eat.
The manatee's lips involve a large, split upper lip. The left and right
sides can move independently to move the food into place-almost like
a separated lip and each one they can use to manipulate things in their
environment very, very well.
or "dentation" of manatees is very unique. They have just
one kind of teeth-- hind molars. And they have what's called "hind
molar progression". also know as "marching molars".
This means that their teeth are constantly moving forward. When the
teeth get to front of the row on both top and bottom, they wear down
from just the chewing--of whatever vegetation they're chewing--and the
roots are resorbed so what they end up with is just a plate. Then by
the time they get to the front of the row the plate falls out and the
next tooth is moved forward. So it's a constant resorption and moving
of the roots up the jaw with new teeth being emerged from the back.
And it's an indeterminant number of teeth.
- How many
teeth do they have? At any one time, it can be about seven per quadrant.
Usually calves have four teeth per quadrant, and as they get larger
they may have seven in each quadrant. But over a lifetime,the number
changes, because that rate of movement is different depending on their
diet, and how much sand is in the area where they're feeding, and how
coarse the vegetation is if they're feeding on coarse grasses you know
their teeth are going to migrate more quickly than they would if they're
just feeding on soft freshwater vegetation most of the time.
to other mammals' teeth, Manatee teeth are very unique. Rather than
having one tooth fall out and then be replaced in the same spot with
another (vertically), Manatee teeth are just continually replaced
horizontally (marching molars). Tooth replacement continues throughout
Manatee nostrils close tightly when they dive under water like a little
valve, a very tight valve in the nostrils (kind of like nose-clips for
come back up to the surface, their nostrils open to take quick, deep breath.
Take a look at this video clip:
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