Help! How come some fish have teeth like humans? | Nature Trumpet

Welcome to the 39th issue of the Nature Trumpet column. In the past half month, we have collected the following natural news and research worth reading:

1) How strange! How can there be a fish with human teeth?

2) 2,000 little penguins found dead on the beach

3) Cocaine thrown into the sea may cause sharks to take drugs

4) Fish are more civilized than humans. They queue up when they encounter traffic jams.

5) Why do hairy caterpillars hurt so much?

6) Great White Shark Pirate, robbing a fisherman

Fish with human teeth

Recently, a little boy in the United States caught a weird-looking fish - it actually had human teeth !

Hello, we have the same teeth | Oklahoma Department of Wildlife Conservation

This fish belongs to the family Serranidae , and the specific species is unknown. People call this kind of fish with strange teeth "pacu fish", and some people in Chinese call them "human tooth fish". They look a bit like piranhas, but they are actually omnivorous fish, mainly eating fruits and nuts , and humans are not on their menu. Researchers believe that it is their dietary attributes that have created this mouth of teeth that are similar to those of humans.

By contrast, this is a piranha that feeds on drowned animals and other fish, with sharp teeth | André-Philippe DP / Wikimedia Commons

The toothfish has a scary nickname - the castrator. It is said that they like to attack men's testicles , which greatly scares naked swimming enthusiasts. However, fish experts say that although the probability of death from being bitten off the testicles by the toothfish cannot be said to be zero, it is obviously much lower than the probability of drowning.

Little boy and toothfish | Oklahoma Department of Wildlife Conservation

After catching the toothfish, the boy immediately released it and contacted the police later. But in fact, this fish is native to South America and is an invasive species in North America and should not be released. People originally brought toothfish to the United States as pets, but some people raised the fish and didn't want them anymore, so they irresponsibly released them into nearby rivers. Toothfish can grow up to 1 meter long and weigh up to 40 kilograms. They compete with local aquatic animals for resources and have an impact on the local ecosystem.

Penguin washed ashore dead

Off the coast of Uruguay, the bodies of about 2,000 penguins were recently discovered.

Penguin dead on the beach | References [2]

The penguins may have starved to death . Environmental department staff conducted autopsies and found that the dead were all young Magellanic penguins , with empty stomachs and no fat reserves. The bird flu test results were all negative, indicating that they did not die of bird flu.

Magellanic penguin | V. Laroulandie / Wikimedia Commons

The starvation of the little penguins may be due to human overfishing . Magellanic penguins are distributed in the temperate regions of South America and feed on squid, krill and other animals. When winter comes in the southern hemisphere, they migrate north to warmer waters to find food . However, human overexploitation has led to food shortages, and they have to swim farther to find food . The thinner little penguins may have starved to death in the sea and eventually washed ashore.

Climate change may also be related to the mass death of little penguins. In July this year, a subtropical cyclone appeared in southeastern Brazil, forming a storm at sea . The young penguins with weaker survival ability may have died in the severe weather. Recently, the bodies of albatrosses, turtles and other animals have also been found on local beaches. They may have also died in the storm.

Cocaine Shark

In June, the U.S. Coast Guard seized more than 6,400 kilograms of cocaine packages from the sea - for decades, criminals have been throwing cocaine packages into the sea to avoid inspection . However, thousands of sharks may have consumed this cocaine and suffered a huge impact as a result.

Smuggling cocaine packages | Petty Officer 3rd Class Cory Booth

Scientists designed a series of experiments to study how these sharks respond to cocaine .

At first, they forged some packages that looked like cocaine packages and placed them together with fake swans. Unexpectedly, the sharks didn't care about the swans at all, but rushed to the packages, and some sharks even dragged the packages away directly - the "cocaine packages" made them more excited than the swan meat .

Cocaine Seized at Sea | US Navy

Next, the scientists made highly concentrated fish meal that would trigger a similar reaction to cocaine, releasing large amounts of dopamine in the shark brain - and sure enough, the sharks were very excited after ingesting it. Finally, they dropped fake cocaine packages from an airplane into the sea to simulate the release of real drugs. As a result, sharks of multiple species rushed to the fake cocaine packages , looking like a drug addict seeing a large bag of drugs.

Shark | Pete Kontakos / Wikimedia Commons

Scientists believe that it is still impossible to determine whether sharks have really taken drugs and developed drug addiction; they need more repeated experiments to verify. In addition to cocaine that accidentally enters the ocean, they are also worried that drugs such as caffeine, birth control pills, and antidepressants that flow into the ocean from urban water may have quietly affected marine animals.

Neon carp line up

Here is an introduction to a very civilized and beautiful little fish. When they encounter congestion, they will queue up obediently.

Genius Fish | Aurélie Dupont

They are neon carps (Paracheirodon innesi), and their colors are as beautiful as neon lights. Scientists put 30 fish in a group in a fish tank and let them pass through openings of different widths. As expected, the fish passed through the wider channel faster. But scientists were surprised to find that no matter how wide or narrow the channel was, the fish would line up in an orderly manner and swim one by one at a constant speed , instead of rushing in and rushing to go first.

Queuing, the channels are very small, ranging from 1.5 cm to 4 cm | Larrieu et al., 2023

Neon characins not only queue up, but also always maintain social distance . Scientists have found that although they gather in front of the passage when queuing, there is no physical contact between the fish. Even in an emergency (with a predator chasing behind), they will not rub shoulders and push each other . In this regard, we humans should also learn from neon characins - crowds and flocks of sheep will always be blocked, and everyone will squeeze like headless flies, which will slow down the evacuation speed.

Sheep: squeeze squeeze squeeze | 3268zauber / Wikimedia Commons

The queuing and evacuation skills of neon carps are similar to those of ants. Scientists believe that this discovery can serve as inspiration for the development of swarm robots and self-driving cars .

Caterpillar with thorns

The caterpillar below may look cute, but if you get stung by it, it will hurt like being beaten with a baseball bat. Scientists recently discovered the secret of their stinging ability - under their furry appearance, they actually have dagger-like spines, and the spines are venomous !

Hey, the last person who touched me was hospitalized | Judy Gallagher / Wikimedia Commons

This is a caterpillar of the family Velvet Moth , and their venom contains aerosol-like proteins . These proteins take on a donut shape before burrowing into human cells, where they break through the cell membrane and stimulate the animal's sensory neurons, causing the animal to suffer excruciating pain .

What's even more amazing is that the caterpillars' toxins may not be native to them, but may have been accidentally "stolen" from bacteria by their ancestors . The structure of caterpillar toxins is exactly the same as that of bacterial toxins. Scientists believe that this may be because bacteria transferred the genes encoding these toxins to caterpillars 4 million years ago - the bacteria first infected the caterpillars and then inserted this DNA into the nucleus of the host cells. This process is called horizontal gene transfer .

Even as moths, they're still furry | Smithsonian Environmental Research Center

This toxin is passed down from generation to generation in caterpillars, indicating that the gene was not implanted in ordinary body cells, but in reproductive cells that happen to be able to become sperm and eggs. In this way, when caterpillars become moths and lay offspring, the offspring will also have this gene . This gene accidentally acquired by the ancestor has been used by caterpillars from generation to generation and has become a powerful weapon to protect them .

Great white shark robs fisherman

Great white shark robbed the fisherman!

Recently, a man caught a 1-meter-long striped bass in Cape Vermont. However, just as he excitedly dragged the striped bass into the boat, a real pirate struck lightning - a 3.6-meter-long great white shark rushed out of the water, bit the big fish hard , and did a somersault at high speed. Then, the striped bass' body and the great white shark disappeared into the water.

Great White Shark: I'll leave you my head as a souvenir, you're welcome | Gavin Varley

The passengers on the boat were all stunned. At this moment, there was only a striped bass head dangling on the fishing line in front of them, and they were all covered with seawater splashed by the shark. All this happened in a flash, and no one had time to react.

The guy holding the fish head (left over by the shark) is smiling so happily (not) | Joshua Martin

This is not the first time a shark has been spotted snatching a striped bass. Just a few days ago, another shark was spotted snatching a striped bass off Cape Vermont.

Great white shark robbed fisherman in the past | Wide Open Spaces

It is the season when great white sharks are catching seals in offshore areas , and tourists have been banned from swimming to avoid being attacked by sharks. However, judging from these incidents, it is not only swimmers who need to be warned, but also fishermen who need to be careful of great white sharks waiting nearby.

References

[1]https://www.livescience.com/animals/fish/rare-piranha-like-fish-with-human-teeth-caught-by-young-angler-in-oklahoma

[2]https://phys.org/news/2023-07-penguins-dead-uruguay-coast.html

[3]https://www.livescience.com/animals/sharks/cocaine-sharks-off-florida-may-be-feasting-on-dumped-bales-of-drugs

[4]https://www.nature.com/articles/s41598-023-36869-9

[5]https://www.pnas.org/doi/10.1073/pnas.2305871120

[6]https://phys.org/news/2023-07-shark-cape-cod-bay-striper.html

Author: Cat Tun

Editor: Mai Mai

Title image source: Oklahoma Department of Wildlife Conservation

This article comes from GuokrNature (ID: GuokrNature)

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