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Scientists solve mystery of the glow-in-the-dark fish’s deadly, see-through teeth

Reuters and AP, June 6, 2019 6:45PM Kids News

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The deep-sea creature's sharp and deadly teeth are see-through underwater and invisible to prey. Picture: AP media_cameraThe deep-sea creature's sharp and deadly teeth are see-through underwater and invisible to prey. Picture: AP

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Scientists have solved the mystery of the see-through teeth of the monstrous, glow-in-the-dark, deep-sea dragonfish.

Dragonfish are ferocious predators at the top of their food chain*, partly because they can hide their jagged, needle-like teeth from their prey. They can also extend their jaws to bite into prey up to half their body size.

Until now, no one has known how their teeth could be invisible.

Using microscopes, scientists studied the teeth of dragonfish they had scooped up from about 500m-1km underwater from the Pacific Ocean off the coast of California, US.

A dragonfish collected by the researchers to study its teeth, which are made of the same material as human teeth but when looked at under a miscrosope, are structured differently, which means they don't reflect light. Picture: media_cameraA dragonfish collected by the researchers to study its teeth, which are made of the same material as human teeth but when looked at under a miscrosope, are structured differently, which means they don’t reflect light. Picture:

They found that dragonfish teeth are made of the same materials as human teeth — a protective layer of enamel on the surface and a tough, deeper layer of dentin*. But the minerals* have a much finer microscopic structure that is not organised in any regular, neat pattern.

“That was very surprising to us,” said Professor Marc Meyers of the University of California, San Diego, who led the research published in the journal Matter.

Deep down underwater it is almost completely dark. Dragonfish light their way by carrying bacteria that make blue or red light. That’s called bioluminescence.

The light from the bioluminescence doesn’t reflect off the teeth because of their messy microscopic structure. Instead, most light passes through the teeth.

“Thus, the mouth is invisible and the prey is caught more easily,” Prof Meyers said.

“Initially, we thought the teeth were made of another, unknown material.

“However, we discovered that they are made of the same materials as our human teeth: hydroxyapatite and collagen. However, their organisation is significantly different from that of other fish and mammals. This was a surprise for us. Nature is amazing in its ingeniosity*.”

Other deep-sea predators, such as hatchetfish and anglerfish (which wave a glowing, rod-like growth from their heads to lure prey) also have see-through teeth.

“These have not been investigated yet, but I suspect they have a similar structure,” Prof Meyers said.

Dragonfish look like monsters but also something like an eel. Picture: AP media_cameraDragonfish look like monsters but also something like an eel. Picture: AP

‘MONSTER’ DRAGONFISH
The scientific name of dragonfish is Aristostomias scintillans.

“They look like monsters,” said Prof Meyers. “But they’re mini monsters” — about as long as a pencil.”

They are thought to grow to about 25cm long.

Nobody has seen a dragonfish in the wild because they live so deep underwater in almost complete darkness.

They are black with an eel-shaped body with a long, fleshy filament* called a barbel hanging from the lower jaw with a bioluminescent organ called a photophore on the end to lure prey.

They also have two rows of photophores along the length of their body.

Their long, sharp teeth are big relative to their body size.

A dragonfish face looks like something out of a horror movie.

They behave in a vicious, aggressive way.

An undated handout photo obtained on July 15, 2010 shows a deep-sea anglerfish, as scientists from the Queensland Brain Institute, using high-tech cameras, photographed sea creatures at a depth of over 1000 metres at the Osprey Reef in the Coral Sea, some 350kms north-east of the northern Australian city of Cairns.  The sea creatures, which live in a dark world where the pressure is 140 times greater than on land, were well adapted to their environment and team leader professor Marshall said ''Learning more about these creatures' primitive eyes and brain could help neuroscientists better understand human vision.''  ''We could also design better cameras and illumination systems because, as we've seen, nature often gets there first.''   AFP PHOTO/QUEENSLAND BRAIN INSTITUTE/Justin Marshall/RESTRICTED TO EDITORIAL USE media_cameraDeep-sea anglerfish also have see-through teeth and this research could help scientists better understand these and other creatures from very deep oceans. Picture: AFP/Justin Marshall

GLOSSARY

  • food chain: line of living things in nature that explains who eats who and what
  • dentin: one of the main ingredients of teeth
  • minerals: non-living natural substance
  • ingeniosity: the quality of being incredibly clever
  • filament: fibre or threadlike object

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QUICK QUIZ

  1. Does anything eat dragonfish?
  2. What does the bacteria carried by a dragonfish do?
  3. How big is a dragonfish?
  4. What is a barbel and what does it do?
  5. Does the dragonfish have a friendly face?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Write a poem
The article describes many features of the dragonfish. Use the information to help write a poem that describes the appearance and behaviour of the dragonfish to someone who has never seen one or never seen a picture of one. Use language that allows the reader to visualise this remarkable creature living deep in the ocean. What does it look like? How does it behave? What is special about its teeth? How do they help it to catch its prey. Don’t identify that you are describing a dragonfish until the last line of your poem. Your descriptive language should intrigue your audience to keep reading to find out what the creature is.

An example of how to start is:

It lurks in the darkness

Deep down in the sea.

A ferocious predator

But not one that we can see.

Time: allow 30 minutes to complete this activity
Curriculum Links: English

2. Extension
Invisible teeth!
Having see-through teeth is probably of great benefit to the dragonfish. But would you want invisible teeth?

Write a list of POSITIVES and NEGATIVES of having invisible teeth. Your list can include serious and more lighthearted ideas.

For example:

Positive — if a tooth gets knocked out — no-one will see that you have a gap.

Negative — tooth fairy would have trouble finding them.

Time: allow 15 minutes to complete this activity
Curriculum Links: English, Critical and Creative thinking

VCOP ACTIVITY
Features
Make a list of all the features or attributes of the dragonfish mentioned in the article. Then pretend someone is writing an article about you and make a list of all your attributes to compare with the dragonfish. Who should be feared more, you or the dragonfish?

HAVE YOUR SAY: Would you like to have invisible teeth like a dragonfish? Why or why not?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.

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