Baby Zebrafish Eyes Work Kind of like Real-Time Photoshop

[ ♪ Intro ] Zebrafish are basically aquatic lab rats. They’re a model organism that scientists use
to study everything from development to disease, in the carefully controlled environment of
a fish tank. Now, researchers are also looking into how
these small, stripy minnows see, and they published a paper about it last week in the
journal Current Biology. This study is the first detailed description
of how vision works in a vertebrate that has 4 kinds of color photoreceptors, not a measly
3 like humans. And they found that, as babies, these tiny
fish have really precise vision that’s more than meets the eye. In fact, it’s tailored to the different
parts of their environment. See, zebrafish are naturally found in clear,
slow-moving water in Asia. They rely on their eyes to find their way
around, hunt, and avoid getting eaten. And baby zebrafish are like all eyes — their
eyeballs make up a quarter of the total volume of their bodies and contain half of the neurons
in their central nervous system. If our babies had similar proportions, their
eyes would be like grapefruit sized. This research focused on the retina, which
is in the back of the eyeball where light-sensitive photoreceptors are found. There are two main types of photoreceptor
cells: rods detect low levels of light but don’t really detect color, and cones work
better at bright levels of light but can detect color. In human retinas, rods and cones are pretty
evenly distributed, except for a region called the fovea where there are more cones and our
vision is a little sharper. But baby zebrafish retinas are more complicated. While human retinas have 3 types of cones
— one sensitive to red wavelengths of light, one to green, and one to blue — zebrafish
have a fourth that’s sensitive to UV light. And in their eyes, different photoreceptors
are concentrated where they’re needed most. Baby zebrafish hang out in shallow water where
death typically comes from above, whether it’s a heron or other predator silhouetted
against the bright sky. So the part of the retina that gets light
from above has more rods, because they just need to see if anything’s coming — not
what color it is. Most colorful things, like rocks or plants,
are in front of or below baby zebrafish. So those areas of the retina have more cones,
especially the ones sensitive to red, green, and blue light. But the single-celled microorganisms that
baby zebrafish eat are translucent, which makes them hard to see with those cones. Except they do reflect a good amount of UV
light. So the parts of the retina getting light from
the strike zone, which is just a cool term researchers use for the horizon of the fish’s
vision, have more cones sensitive to UV light. Basically, all these retinal regions chunk
up the world, so different parts of the image have boosted color or contrast like Photoshop
manipulation of the world in real time. And this probably plays a big role in helping
them survive, otherwise they wouldn’t have evolved to be this way. When baby zebrafish mature, though, they grow
into their eyes, move into deeper water, and kind of lose their vision superpowers. Their retinas change to be more like ours,
where different cones are redistributed in a more even pattern. But not all fish have good eyesight! The baby whale fish sounds like a poorly named
bathtub toy, and I guess it’s kind of stubby and cute and whale-like. But unlike zebrafish, it lives in muddy rivers
in Central Africa where visibility isn’t so great. So instead of relying on its eyes, it uses
electricity to get around. And according to new research published in
the journal Current Biology last week, knowing how these fish use electricity may give us
insight into some serious human diseases. Several species of fish use electricity to
communicate and sense what’s nearby, kind of like echolocation. And to do that, they have electric organs
with specialized cells called electrocytes, which can generate action potentials like
muscle cells and nerve cells. Action potentials occur when ions rapidly
cross cell membranes and alter the electrical charge. And when a whole bunch of electrocytes do
this simultaneously, they can emit an electrical discharge. But ions can’t cross the cell membrane just
anywhere. They have to pass through special proteins
called ion channels, which are like carefully controlled doors. Now, baby whale fish can generate extremely
quick electric pulses that are only 2 ten thousandths of a second long. They have to keep it short so they can stay
hidden from catfish, which can also sense electricity and will totally eat them. So these researchers wanted to know how baby
whale fish make these extremely short action potentials, so they took a closer look at
the KCNA7 potassium ion channel. Humans have this same protein in our heart
and muscle tissues, but the baby whale fish has a slightly different version. The researchers discovered a negatively charged
patch of amino acids in the fish’s ion channel that makes it more sensitive and able to open
more quickly. Understanding how slight differences in these
ion channels affect how they work might someday help scientists treat diseases like epilepsy,
and certain heart rhythm and muscle disorders. These conditions are linked with genetic mutations
that also change how potassium ion channels work. So maybe understanding this odd little fish
will help scientists find a fix. Thanks for watching this fish-filled episode
of SciShow News! If you’d like to stay up to date on the
latest research in all fields of science, from aquatic vertebrates to human medicine,
we post these News episodes every Friday! Or you can stick around for all of our videos
including the hundreds we’ve already uploaded at where you can subscribe. [ ♪ Outro ]


  1. Fun fact: Some humans are born with the ability to see 4 colors, for all you lucky woman out there have fun seeing the world like “theoretically” no man ever has.

  2. 2:29 Nope; hasty generalization fallacy
    2:56 What, were Blue Öyster Cult, Grand Funk Railroad and Electric Light Orchestra already taken?

  3. I was braiding zebrafish for a while and yeah when you find the babies they're nothing but eyes they also like to jump out of the tank when they get older

  4. *ahem~. Well actually, our "red" cones are most sensitive to yellow light, not red light. Each of the three types is sensitive to the whole visual spectrum with their sensitivities like a bell/normal/Gaussian curve. In fact, the sensitivities of the 'red' and 'green' ones are very close and have huge overlap. So for the eye to determine the hues around the greeny-yellowy-redy end of the spectrum, it's more mathematically involved than a simple mix of primary colours.

  5. Question: for SciShow If we ,as homo sapiens , are all related due to Mitochondrial Eve why are there so many different colors of skin?

  6. Is it just me or did Hank sound a little bit unenthused in this episode? Not that he should be but I just noticed it.

  7. Do fish feel or sence anything when humans are swimming in the water? Because our potassium channels aren't adapted to any intelligible means of communication. Given the depth in water to meet an electric fish, our heart and lungs ions probably would not diffuse into the water. I imagine either sodium or potassium diffusion could have sometime, (or at least for humors sake) accidentally caused a fish to start a really bad rumor of humans.

    intelligent fish
    (Speaking in potassium ion diffusion among, let's say, catfish)
    "Wow those creatures communicate badly, and they're loud, what is the loud for?"

  8. My University has a huge zebrafish lab lol. They have the local school kids raise their own fish when they learn reproduction in like 7th grade.

  9. Imagine if Zebrafish's vision with 4 photoreceptors is so great then how Godly of a vision a Mantis Shrimp would have.

  10. pretty evenly distributed except for the fovea isn't really accurate there for humans. It's mroe like a gradient towards the fovea and then another pretty harsh increas in cones

  11. Why don’t you make a video on the alternative theories about the Universe on YouTube this would be interesting and good for the YouTube community!!!

  12. So you're saying these electric baby whale fish use their current biology to sense their surroundings?

  13. Hey sci show I have a question
    Can we use CO2 for making energy …..or convert it into something that can be use as energy

  14. it would be amazimg if we have a synthetic image rendered according to how the zbra fish ratina map the world i mean does zbra fish brain process 3 type of signals at the same time it is very complicated for a fish taking in account that also the fieled of view for sea creatures is 180 per eye

  15. So if you're a tetrachromat (most likely) gal, does that make you an honorary zebra fish? Does it work the same way for humans?

  16. did a neuroscientist join the scishow team recently? This suddenly got real close to home. 🙂

  17. 3:12 "Current Biology?" Is this for only for fish and animals living with currents of water, animals that can generate electricity, or just the most recent biology developments?

  18. Weird question: would humans be healthier if we didn’t practice medicine at all? Speaking broadly, very broadly, would dominant traits that help us survive be more relevant if people with life-altering diseases weren’t helped? I know this sounds very bad but it’s just a thought lol

  19. Hey guys, just a reminder that Epilepsy isn't a disease, it's a neurological condition. You wouldn't call autism or ADHD a disease, either.

  20. All these amazing abilities! It's as if evolution has an ultra genius brain and went on a creation frenzy! Gee, what are the odds?

  21. What's wrong with your voice? Are you sick Hank? It's still a great job, but comparing to your previous video's which are way more energetic and your voice has lowered allot.

  22. Good to hear about the baby whale. My sister actually has a problem with her ion channels so it's reassuring to get news on such research

  23. At :50 Their eyes contain half of the neurons in their central nerve system. This really needs to be checked out intensively.

  24. 1:08 . You just answered a question I've wondered for ages. I've wondered why dim light is never just a less bright version of the vibrant colours we see. It's always muted and dull. Interesting.

  25. Have you guys ever used that greyscale/monochromacy setting turned on for a while? Once you turn it off, things look more vibrant.

    Try doing this in a dark room, just doing something basic for a while. Then when a good amount of time passed by, like about 5 or more minutes, turn the monochromacy off, and look at something with a lot of color, or basically any of the stuff you already saw in greyscale.

    I guess my point is this could probably help us to sort of see like an animal with more cone cells

  26. This made me happy. First, it was all about fish, which is a rare and pleasant surprise. Second, you mentioned the baby whale fish research possibly helping with a disorder my mom has, though hers is injury-induced, not hereditary.

  27. so by understanding this we can maybe genetically engineer and enhance humans to have UV and IR cones evenly scattered in their eyes as well so these enhanced humans might have night vision.

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