National Geographic: The Body Changers Page #2

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In a single magical hour,

an adult struggles out.

At first, its goggle eyes look like

deflated beach balls.

But soon they are pumped up

to full size,

some of the keenest eyes

in the insect realm.

In the remaining hours before dawn,

the dragonfly pumps blood

into its soft, wet wings,

doubling their length.

The dragonfly has changed from

a jet-powered aquatic hunter

armed with a hydraulic spear

to a peerless aerialist

that will stalk on the wing.

About two hours after emerging,

the dragonfly takes flight.

Once master of the pond bottom,

the dragonfly now controls

the air space above.

No other insect devotes as big

a share of its body weight

to flight muscles as the dragonfly.

Scuba certification has been traded

in for a pilot's license.

As larvae,

dragonflies once hunted tadpoles.

Adult frogs sometimes have the chance

to even the score.

A dragonfly is a curve ball

on the wing.

There's nothing wrong with

the occasional whiff

if now and then you connect with

a solid double.

Just as body changes can take place

in individual creatures,

so they can occur across generations.

That's evolution.

Natural selection is the long process

of picking winners and losers

among organisms that differ slightly

from their parents.

Without body-changing over generations,

evolution would come to a standstill.

As it is, change adds to change

to create the entire parade of life.

Life may have begun with a blob

that by chance transformed.

When alterations were successful,

the transformer thrived

and transformed again.

One of natural selection's

winning picks

is the trick of morphing

during a single lifetime.

Plankton is a potpourri of larvae,

body changers of many species

at an early stage of life.

Creatures like this have an edge:

each stage can be honed

for a different job.

Now they are shaped for spreading

around-drifting on the currents.

Soon these beasts will be changed

beyond recognition

into new forms tailored

for feeding and reproduction.

One member of the plankton,

a crab larva,

starts life with scant

resemblance to its parents.

It shares the ocean with

another tiny drifter, the seaslug.

This relative of the snail

hatches wearing a transparent shell,

a suit of crystalline armor.

Seaslug and crab, similar as larvae,

may confront each other as adults,

as different as two animals can be.

Having shed its shell,

the seaslug eventually becomes

an adult four inches long.

It now has a new organ,

a feeding hood.

The billowy hood caresses eel grass

to catch food like skeleton shrimp.

Like a submarine Venus fly trap,

the seaslug closes up,

trapping prey like skeleton shrimp

with a zipper like seal.

Growing on the seaslug's back

are other new organs,

fleshy paddles

that will soon save its life.

As the seaslug feeds,

it is being watched

by its former plankton mate.

The crab has changed into

a formidable scavenger

with molar-like grinders on its claws.

Blind except perhaps to light and dark,

the seaslug approaches danger.

The crab pinches at the seaslug,

as hard to grab as a water balloon.

Finally the crab gets purchase.

But it gets only

a small serving of seaslug,

whose paddles pop off by design.

The seaslug swims away

with wild undulations.

Only a stump remains

where once there was a paddle.

The missing organ

may eventually grow back.

Once a tiny drifter, this body changer

is now rebuilt for escape.

Up the water column without a paddle,

the seaslug leaves the crab,

its fellow transformer,

with a meager souvenir.

Transformation is not

just the privilege of living things.

The morphing of clouds may offer

nothing more than delight.

The morphing of bodies serves

a more important goal: survival.

In the Arizona desert,

the weather shifts late in June.

After eight crispy months,

skies darken.

The monsoon has arrived.

The pounding of the rain has stirred

strange creatures beneath the soil.

In this small, evaporating pond,

animals race against the clock

to transform.

Tadpoles of the spadefoot toad

must absorb their tails,

grow lungs, sprout legs.

They must transform from

fish-like swimmers

with gills to hopping air-breathers.

If changing from tadpole to toad

isn't miracle enough,

tadpoles of this species have two ways

to do it,

the nice way and the not so nice.

In this hot summer,

the pond is shrinking quickly.

It could become a death-trap,

a cauldron of bouillabaisse.

As the water level drops,

time is running out

for the tadpoles to become toads.

Meanwhile, another creature

joins the fray.

Fairy shrimp may have lain dormant

underground as eggs for years,

waiting for just the right conditions

to rush through their lives.

As the pool dries up,

it gets more crowded.

Tadpoles bump into more and more of

these crustaceans.

Advantage:
tadpole.

If they end up snacking on

lots of Sonoran scampi,

the tadpoles sense that their pond

is shrinking fast.

There's something about fairy shrimp

that throws a chemical switch

inside some of the tadpoles.

And these gentle browsers now

begin to transform into brutes

that will stop at nothing

to become a toad.

Some of the tadpoles are

turning into cannibals!

This is body-changing with attitude.

The cannibals are lighter

in color and larger.

A huge muscle forms in the jaw,

the better to grab their neighbors with.

We're no longer on golden pond.

The cannibals grow at breakneck speed

on their unneighborly diet.

On the fast track, they will need only

two and a half weeks to become toads.

The slower, mild-mannered tadpoles

need six weeks to grow up.

The extra time helps them become

healthier adults than the cannibals.

But often in the desert,

time is a luxury.

And the race goes to

the swift and brutal.

It was a remarkable turning point

in evolution

when a fish transformed

to emerge from the sea,

gulp air and drag itself around.

But what took eons in evolution is an

everyday occurrence in tadpoles.

To reach adulthood, spadefoot toads

must live fast and hard,

then dig down into cool damp soil

before the next drought arrives.

For others in the desert,

the season of change has also arrived.

On an acacia blossom, an egg barely

visible to the human eye hatches.

A bristled beast emerges.

This caterpillar has a problem.

If it's ever going to become

a butterfly,

it must first survive its life

as a larva.

The desert is alive with predators

like ants and wasps.

This caterpillar has

an ingenious defense.

It will soon enlist one of its enemies,

but only after it transforms to develop

special organs for manipulating ants.

At the base of the acacia tree,

ants have dug a nest.

Most ants like nothing better than

dismantling caterpillars.

But these ants love them, intact.

They will protect the caterpillar.

That's because the ants march to

the beat of a different drummer.

The caterpillar has become

the drummer.

This is the sound

the caterpillar makes

with body vibrations

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