The fish that walk on land - Noah R. Bressman
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0:07 - 0:11This pond is the only home
this fish has ever known. -
0:11 - 0:15But lately, it’s gotten crowded
and food is scarce. -
0:15 - 0:18Luckily, it has an option many don’t:
-
0:18 - 0:22as a walking catfish, it can dance
its way out of the water -
0:22 - 0:25and onto bigger and better things.
-
0:25 - 0:30However, it faces many challenges
on its terrestrial journey: -
0:30 - 0:33it’s now in danger of suffocating,
drying up, -
0:33 - 0:36suffering physical damage
from rough terrain, -
0:36 - 0:38and being hunted by land predators.
-
0:40 - 0:43We think of fish
as completely aquatic animals. -
0:43 - 0:48But the walking catfish is just one
of hundreds of fish species -
0:48 - 0:51that are actually amphibious,
-
0:51 - 0:56meaning that they possess adaptations
that enable them to survive on land. -
0:56 - 1:00Fish amphibiousness is a spectrum.
-
1:00 - 1:04At one end are species
like the mosquitofish -
1:04 - 1:06that’ll only move on land when forced.
-
1:06 - 1:10And at the other end
are species like mudskippers -
1:10 - 1:14that nonchalantly hop around mudflats
for days at a time. -
1:14 - 1:19But why do fish make the exodus
from water to land? -
1:19 - 1:22And how do they cope
with this drastic transition? -
1:24 - 1:28If temperatures get too high
for the mangrove rivulus -
1:28 - 1:31in the shallow tropical pools
it inhabits, -
1:31 - 1:36it’ll flip itself onto a bank
and cool off in the shade. -
1:36 - 1:37During the dry period,
-
1:37 - 1:41it can survive for two months
out of the water -
1:41 - 1:44by staying in moist environments.
-
1:44 - 1:48Meanwhile, the eel catfish
makes its onshore voyage -
1:48 - 1:52to satisfy its hearty craving for beetles.
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1:52 - 1:57And for others, the terrestrial draw
is more ritualistic. -
1:57 - 1:59Every year under the cover of night,
-
1:59 - 2:05masses of California grunion flop
their way onto sandy beaches, -
2:05 - 2:09where females deposit thousands of eggs
into the sand -
2:09 - 2:12before re-entering the ocean.
-
2:12 - 2:15Underwater, fish breathe with gills,
-
2:15 - 2:19which are feathery organs
packed with blood vessels -
2:19 - 2:22that absorb dissolved oxygen
from the water. -
2:22 - 2:27But in the open air, their gills collapse
and are rendered useless, -
2:27 - 2:31so amphibious fishes need
other ways to breathe. -
2:31 - 2:35The armored catfish’s stomach
is packed with blood vessels, -
2:35 - 2:40so it can gulp down air
and breathe through its stomach lining. -
2:40 - 2:45And lungfish, being related
to the ancestors of all tetrapods, -
2:45 - 2:49or four-limbed vertebrates,
are equipped with true lungs. -
2:49 - 2:53They’ll actually drown
if they’re kept underwater too long. -
2:55 - 3:01Fish have thin, permeable skin
that allows for essential compounds -
3:01 - 3:05to diffuse into and out of their bodies
while they’re underwater. -
3:05 - 3:10But this works against them on land
as their bodily moisture -
3:10 - 3:12diffuses into the air.
-
3:12 - 3:17To dodge dehydration, mudskippers
roll in the mud like puppies. -
3:17 - 3:20But the lungfish takes the cake:
-
3:20 - 3:24the rivers it inhabits disappear
during dry seasons, -
3:24 - 3:30so it buries itself in the earth
and coats its body in a mucus cocoon. -
3:30 - 3:34It can survive like this for years
until being resuscitated -
3:34 - 3:37by the next big rainstorm.
-
3:37 - 3:42Amphibious fishes use powerful fins
to move on land -
3:42 - 3:45and clever tools to navigate as they go.
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3:45 - 3:50The Nopoli rock-climbing goby,
no bigger than a few centimeters, -
3:50 - 3:54scales hundred-meter-tall
Hawaiian waterfalls, -
3:54 - 3:58inching its way up by alternately
attaching the suction cups -
3:58 - 4:01on its mouth and pelvic fins.
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4:01 - 4:05To find water while on land,
the mummichog, -
4:05 - 4:10like most amphibious fishes,
is on the lookout for reflective surfaces. -
4:10 - 4:13Other species, like mosquitofish,
-
4:13 - 4:18exercise their inner ear to determine
where they’re oriented on a slope, -
4:18 - 4:24relying on the probability that they’ll
find water by moving downhill. -
4:24 - 4:26Our walking catfish, meanwhile,
-
4:26 - 4:31uses the taste buds that coat
its body for navigation. -
4:31 - 4:34These taste buds are concentrated
in its whiskers, -
4:34 - 4:36which whip through the air,
-
4:36 - 4:40sensing compounds that signal
the proximity and quality -
4:40 - 4:43of nearby water— and prey.
-
4:43 - 4:48The walking catfish will shimmy towards
attractive volatile amino acids -
4:48 - 4:54while steering clear of foul waters
emanating hydrogen sulfide. -
4:54 - 4:59While amphibious fishes face a multitude
of new challenges upon leaving the water, -
4:59 - 5:03they’ve evolved ingenious ways
to overcome them. -
5:03 - 5:06They’re resilient in the face
of droughts and floods -
5:06 - 5:10and have access to new prey
as well as a plan B -
5:10 - 5:16if they need to escape competitive,
polluted, or unhealthy environments. -
5:16 - 5:20While being a “fish out of water”
is generally regarded as a bad thing, -
5:20 - 5:24for these species,
it offers an undisputed edge.
- Title:
- The fish that walk on land - Noah R. Bressman
- Speaker:
- Noah Bressman
- Description:
-
View full lesson: https://ed.ted.com/lessons/the-fish-that-walk-on-land-noah-r-bressman
We think of fish as completely aquatic animals. But there are actually hundreds of fish species that are amphibious, meaning that they possess adaptations that enable them to survive on land. Once on land, however, they face suffocation, drying up, and being hunted by land predators. So why do fish make the exodus from water to land? Noah R. Bressman explores the ingenious ways these fish survive.
Lesson by Noah R. Bressman, directed by Anna Benner.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:26
Elise Haadsma approved English subtitles for The fish that walk on land | ||
Elise Haadsma accepted English subtitles for The fish that walk on land | ||
lauren mcalpine edited English subtitles for The fish that walk on land |