The weird and wonderful metamorphosis of the butterfly - Franziska Bauer
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0:12 - 0:15In order to become a butterfly,
-
0:15 - 0:18a caterpillar’s body dissolves
almost completely -
0:18 - 0:22and is rebuilt from its own juices.
-
0:22 - 0:26As inconvenient and even downright
dangerous as this process sounds, -
0:26 - 0:28it’s actually quite common.
-
0:28 - 0:32Butterflies are just a few of
the 800,000 insect species -
0:32 - 0:37that transition from larvae to adults
through complete metamorphosis. -
0:37 - 0:45That’s approximately 85% of insects
and 70% of all known animal species. -
0:45 - 0:48But how exactly does
a caterpillar become a butterfly? -
0:48 - 0:51When a caterpillar hatches
from an egg, -
0:51 - 0:53it has none of a butterfly’s
physical traits. -
0:53 - 0:59It does have groups of cells
inside its body called imaginal discs -
0:59 - 1:03that will eventually
become its butterfly parts. -
1:03 - 1:06For now, these cells remain dormant.
-
1:06 - 1:08Juvenile hormone suppresses
their activity, -
1:08 - 1:13and prevents the caterpillar
from beginning metamorphosis too early. -
1:13 - 1:16Immediately after hatching,
the caterpillar begins to feed, -
1:16 - 1:22building up fat until its rigid skin,
called a cuticle, becomes too tight. -
1:22 - 1:28At this point, a hormone called ecdysone
triggers the cuticle to shed, or molt. -
1:28 - 1:33As the caterpillar grows,
it usually molts four times. -
1:33 - 1:35Then, when it’s nice and plump,
-
1:35 - 1:38the caterpillar’s levels
of juvenile hormone drop, -
1:38 - 1:41which triggers it to stop
eating and moving. -
1:41 - 1:43A final burst of ecdysone
-
1:43 - 1:48prompts the caterpillar’s cells
to begin to self-destruct. -
1:48 - 1:53Soon, the muscles, fat, and other tissues
are almost entirely liquefied, -
1:53 - 1:58though the imaginal discs stay intact
and begin to grow. -
1:58 - 2:03At the same time, a second skin layer
called the pupal cuticle -
2:03 - 2:05forms underneath the first.
-
2:05 - 2:10One more molt exposes
the hard exterior of the pupa. -
2:10 - 2:14Besides the imaginal discs,
only a few tissues are spared, -
2:14 - 2:16including parts of the respiratory system,
-
2:16 - 2:17the heart,
-
2:17 - 2:18some abdominal muscles,
-
2:18 - 2:21and the mushroom bodies of the brain.
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2:21 - 2:26The caterpillar juice then fuels
the development of the imaginal discs -
2:26 - 2:26into eyes,
-
2:26 - 2:27antennae,
-
2:27 - 2:28legs,
-
2:28 - 2:29wings,
-
2:29 - 2:30genitalia,
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2:30 - 2:31and other body parts.
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2:31 - 2:36Once its new body is built,
the insect molts one last time, -
2:36 - 2:38shedding the pupal cuticle.
-
2:38 - 2:42From there, it’s free to fly away
a new butterfly. -
2:42 - 2:44Even after such a dramatic transformation,
-
2:44 - 2:49the butterfly does retain some memories
from its caterpillar days. -
2:49 - 2:51It’s likely the mushroom bodies
of the brain -
2:51 - 2:57carry important knowledge from the
caterpillar over to the adult butterfly. -
2:57 - 3:00How did such an involved developmental
process come to be? -
3:00 - 3:02We don’t know for sure.
-
3:02 - 3:06The leading theory is that the caterpillar
is actually a drawn-out version -
3:06 - 3:12of a life stage that takes place
inside the egg for some other insects. -
3:12 - 3:15According to this hypothesis,
over millions of years, -
3:15 - 3:21the larvae evolved the ability
to eat and live outside the egg. -
3:21 - 3:24Regardless of how complete
metamorphosis originated, -
3:24 - 3:30it’s become part of the life cycles of
a dizzying number of insect species. -
3:30 - 3:33Still, plenty of species get along
perfectly well -
3:33 - 3:35with a simpler developmental process.
-
3:35 - 3:39What survival advantages might
complete metamorphosis provide -
3:39 - 3:42to make up for the added hassle?
-
3:42 - 3:44For one, it keeps larvae and adults
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3:44 - 3:48from competing for the same habitats
and food sources. -
3:48 - 3:51And while the pupa may seem vulnerable,
-
3:51 - 3:54this immobile stage
can actually be a good way -
3:54 - 3:57to pass parts of the year
when food is scarce. -
3:57 - 4:02To us, a butterfly’s metamorphosis
might sound as fantastic -
4:02 - 4:04as a phoenix rising from its ashes.
-
4:04 - 4:08But these transformations are taking place
all around us, all the time. -
4:08 - 4:10From the Hercules beetle
-
4:10 - 4:11to the honey bee
-
4:11 - 4:12to the garden ant,
-
4:12 - 4:16countless squishy larvae dissolve
and emerge -
4:16 - 4:20as armored, aerodynamic,
and nimble adults.
- Title:
- The weird and wonderful metamorphosis of the butterfly - Franziska Bauer
- Description:
-
View full lesson: https://ed.ted.com/lessons/the-weird-and-wonderful-metamorphosis-of-the-butterfly-franziska-bauer
In order to become a butterfly, a caterpillar’s body dissolves almost completely and is rebuilt from its own juices. Butterflies are just a few of the 800,000 insect species that transition from larvae to adults through complete metamorphosis. But how exactly does this process work? Franziska Bauer explains how these squishy larvae emerge as armored, aerodynamic, and nimble adults.
Lesson by Franziska Bauer, animation by Avi Ofer.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:03
Michelle Mehrtens edited English subtitles for The weird and wonderful metamorphosis of the butterfly - Franziska Bauer | ||
Michelle Mehrtens edited English subtitles for The weird and wonderful metamorphosis of the butterfly - Franziska Bauer | ||
Michelle Mehrtens edited English subtitles for The weird and wonderful metamorphosis of the butterfly - Franziska Bauer | ||
Elizabeth Cox approved English subtitles for The weird and wonderful metamorphosis of the butterfly - Franziska Bauer | ||
Elizabeth Cox accepted English subtitles for The weird and wonderful metamorphosis of the butterfly - Franziska Bauer | ||
Michelle Mehrtens edited English subtitles for The weird and wonderful metamorphosis of the butterfly - Franziska Bauer |