Now properly classified, this tiny, translucent fish could help unlock our brains’ secrets

For years, brain researchers didn’t realize they were studying a fish previously unnamed by the scientific community.

By Michael MarksOctober 5, 2021 7:14 am, ,

The tiny, translucent fish, Danionella cerebrum, wasn’t so much discovered recently as it was – finally – correctly classified by scientists. For years, researchers have used it to study the brain, but those researchers weren’t fish experts, and they didn’t realize they were working with a species previously unnamed by science.

Kevin Conway is an associate professor and ichthyologist at Texas A&M University. He tells Texas Standard that neurophysiologists use Danionella for brain research because of its unique characteristics: it has a complex nervous system for its size and no skull, which gives them easy access to brain tissue. Listen to the interview with Conway above or read the transcript below to learn more about why properly classifying this fish species is crucial for their research.

This interview has been edited lightly for clarity.

Texas Standard: How was the Danionella fish finally “discovered” by scientists?

Kevin Conway: This fish has been used now for around the last five years by neurophysiologists. And on the outside they look very similar to different species of Danionella, and it’s only by studying their skeleton that we actually realized that the neurophysiologists might actually be working with a new species, one that hasn’t been described before. And so, it was swimming in the tanks of neurophysiologists before it’s actually been given a name.

So you’re saying that there was a new species literally swimming right underneath researchers’ noses?

Yes, but this these researchers are not taxonomists, so you have to forgive them for that.

Can you describe this fish, because that’s an important part of of this story, right?

These fishes are tiny. They’re just a little longer than your thumbnail. They are translucent; you can see through them and they have an incredibly reduced skeleton where many bones are actually missing. They just simply don’t form. And that’s including the bones that cover the brain – the skull roof. So this leaves the brain basically covered by a very thin layer of skin, which is useful to neurophysiologists because they can have easy access to this organ. And they can do this at a cellular level because this fish is so small.

Why is this news of special interest to neuroscience?

The cool thing about Danionella is not only that they’re small and have translucent bodies, but they also have very complex behaviors. So, adult males can actually make sound, and it’s involved in male-male interactions. So having a tiny body with an easy, accessible brain combined with complex behaviors is, it’s just really a fortuitous combination of characters, especially for studying how information is processed in the brain.

How firm is the relationship between what happens with these fish and what happens with humans? Are there potential implications for human medicine?

The brain of Danionella is much smaller and much simpler than the brain of a human. But the brains of all vertebrates share a similar cellular makeup, and they also process information in a similar way. And so, by studying Danionella, we could probably learn something about the brains of all vertebrates.

You’re part of a team that gave this fish its scientific name. What’s that process like when you’re doing it collaboratively?

We can communicate very easily across across the world. It’s actually harder to come up with a name in the first place. You want to pick a name that’s appropriate, something that tells you something about this species. And we came up with “cerebrum” as a nod to to the neurophysiologists that have been studying this tiny, tiny brain in this tiny fish.

Could you explain to the layperson why it’s important that we take note of these minute differences between different species?

It’s important that we we know all of the species that we share the planet with. But in this particular example, I can foresee a scenario where different groups of neuroscientists are actually working with different species that they think [are] the same. And that could lead to problems because they may obtain different results and they might scratch their heads and not understanding why. But it’s because they are working with different species that maybe have different characteristics.

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