Mystery solved: Scientists finally know why deep sea coral glows


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If you were to dive 148 feet below the ocean’s surface – into the twilight mesophotic zone – you would see corals glowing green or orange around their mouths or on the ends of their tentacles.


Scientists have long known that corals glow fluorescent in the deep, but, until recently, they didn’t know why. Now, a new study published in Communications Biology last month has an answer: to attract prey.


“The study proves that the glowing and colorful appearance of corals can act as a lure to attract swimming plankton to ground-dwelling predators, such as corals, and especially in habitats where corals require other energy sources in addition or as a substitute for photosynthesis (sugar production by symbiotic algae inside the coral tissue using light energy),” study co-author and research supervisor  Professor Yossi Loya from the School of Zoology and the Steinhardt Museum of Natural History at Tel Aviv University said in a press release.


Biofluorescence is the ability of living organisms to give off light after absorbing energy in some way, The Times of Israel explained. It differs from bioluminescence, which is a glow created by a reaction between an enzyme like luciferase and a molecule that releases light. However, the two properties can have similar purposes such as attracting prey or mates or camouflaging from predators.


Fluorescence in corals is well documented, but mysterious. Scientists have developed various hypotheses to explain the phenomenon, according to ScienceAlert. These include the “sunscreen” hypothesis that the fluorescence helps protect corals from heat or light after bleaching and the suggestion that the fluorescence aids photosynthesis.


But when researchers tested these hypotheses on the corals that live between 98 and 492 feet below sea level, they found no evidence to support either.

“[C]oral fluorescence in deeper habitats creates a gap in our understanding of the widespread phenomenon,” the study authors wrote.


The University of Tel Aviv-led research team, with help from the Steinhardt museum of Natural history and the Interuniversity Institute for Marine Sciences in Eilat, suspected that the corals might be using their glowing abilities to lure prey, as the press release explained. To test this, they conducted the study in three steps.


First, they tested in the lab whether common coral prey were attracted to fluorescence. They used the crustacean Artemia salina and found that it preferred a green or orange fluorescent target to a clear target. When presented with two clear targets, the animal showed no preference. The results were the same with a different Red Sea crustacean, but fish–which are not known coral prey–stayed away from the fluorescent targets.


Next, the researchers tested the plankton at a depth of around 40 meters (approximately 131 feet), which is the corals’ natural habitat. In this environment, the creatures were also more attracted to green or orange fluorescent traps, which caught twice as many of them as the clear traps.


Finally, the researchers gathered corals from 45 meters (approximately 148 feet) in the Gulf of Eilat in the Red Sea. They found that the corals displaying green fluorescence caught 25 percent more prey than corals displaying yellow fluorescence.


“Despite the gaps in the existing knowledge regarding the visual perception of fluorescence signals by plankton, the current study presents experimental evidence for the prey-luring role of fluorescence in corals,” study leader Dr. Or Ben-Zvi of Tel Aviv University said in the press release. “We suggest that this hypothesis, which we term the ‘light trap hypothesis’, may also apply to other fluorescent organisms in the sea, and that this phenomenon may play a greater role in marine ecosystems than previously thought.”


The research findings come as corals–including deep reef corals–are under a myriad of threats. Deep corals in particular are vulnerable to bottom-trawl fishing, offshore oil and gas production, the possibility of deep sea mining and the climate crisis, as Sandra Brooke of Florida State University wrote in The Conversation.


“Ocean currents circulate around the planet, transporting warm surface waters into the deep sea. Warming temperatures could drive corals deeper, but deep waters are naturally higher in carbon dioxide than surface waters. As their waters become more acidified, deep-sea corals will be restricted to an increasingly narrow band of optimal conditions,” Brooke wrote.


This article originally appeared on and was syndicated by


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70 wild, weird facts about the world



world is weird, as are people and even animals.

laws about tying up your giraffe in Atlanta to a precious metal
lurking in your blood, there are endless bizarre wonders you may not
know about the world around you – and a few out in the heavens as

Learn about the first mobile historical monument, an elephant
herd in mourning and more with these 70 incredible and weird facts.

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LagunaticPhoto / istockphoto


In what must have been the cutest science experiment of all time,
discovered that rats laugh when tickled.


Supersmario / istockphoto


In experiments not even remotely as cute as tickling rats, scientists have discovered that mosquitoes urinate on us while feeding on our blood. They’re exploring ways to prevent this, and thereby control the spread of
dengue fever, yellow fever and other diseases.


Looking to gain radioactive super powers? Try a banana! Bananas are
very slightly
radioactive and are even used to measure doses of radiation. BED
stands for Banana Equivalent Dose.


If you had to guess which animal was packing 32 brains, you’d
probably guess wrong. The answer is leeches,
which have a brain in each of their 32 body segments.


While elephants may have just one brain, they use theirs in some truly lovely ways. When “elephant
whisperer” Lawrence Anthony died, an entire herd of
elephants arrived at his house, apparently in mourning.


The Sahara desert is one of the hottest, driest places on Earth, so snowfall is understandably rare. In fact, there are just a handful of recorded snowfalls in living memory – the first on Feb. 18, 1979, another in December, 2016, and the latest on Jan. 9, 2018.


Researchers found that roughly one in every 10,000 chickens is
meaning they hatch half-male and half-female.

According to scientists at the Roslin Institute and the University of Edinburgh, Scotland, bird cells are different to mammal cells in that they don’t need to be programmed by hormones. This means that chicken cells can remain inherently male or female, so a half-and-half chicken could have different plumage on one side than the other based on the gender coding of the cells, along with different body shape, muscle structure and even wattle and spur structures.


volody10 / istockphoto


Farmer Lloyd Olsen failed to kill a rooster once, resulting in a chicken that lived without the majority of his head being attached to his body. That chicken became
famous,, touring the country as Mike
the Headless Wonder Chicken
from 1945 to 1947.


Everyone records over their favorite tapes accidentally – even
NASA it turns out. The tapes containing the original footage of the Apollo
11 moonwalk were probably erased and reused to record satellite
data. Oops!


Scientists performed an
experiment where they shone a bright light on the backs of
people’s knees. Those treated with the light had their biological
clocks “advanced or delayed up to three hours.”


Whales and dolphins take being “right-brained” or
“left-brained” to the extreme. Getting a nap in the
ocean requires them to let one
half of their brains sleep at a time, while the other half keeps
them conscious.


Peru, on the edge of the Atacama desert, is one of the driest places
on earth, leaving hundreds of thousands of people with no access to
clean water. But a team
of engineers
set out to change that – with a billboard. The
billboard changes humidity in the air into clean drinking water.


The Aztecs founded Tenochtitlan in 1325, but there’s a school that
predates them. The University
of Oxford became a full-fledged university in 1249.


We all have a little gold in us. The human body contains about 0.2
milligrams of gold, mostly in our blood.


Speaking of gold, we’re running
low. We’ve probably got less than 15 years of easily mineable
gold left in the world.


One option for when gold becomes harder to mine is to take our cue
from the Aztecs, who valued feathers
much more highly.


You can’t sneeze
while you sleep
. During REM sleep certain neurotransmitters
actually shut down and your brain can’t receive the signal to sneeze.


In 2010, a Nepalese telecom installed eight 3G
base stations along the route up Mount Everest, with the highest
located at 17,000 feet.


Most pregnancies last 280 days or so, but back in 1945, Beulah Hunter reportedly shattered
that norm when she gave birth after being pregnant
for 375 days, or about 12.5 months.


Even Captain Kirk might want to steer clear of this blue
planet. In 2013 astronomers found a deep azure planet where “it
possibly rains liquid glass sideways amid 4,500 mph winds.”


NASA and the Space Telescope Science Institute (STScI)


Would you like more hours in your day? Wait a mere 140 million years
and the average earth day could be 25
hours long because the planet is very, very slowly decelerating.


Your tongue has a unique “print,”
just like a fingerprint.


Deagreez / istockphoto


Don’t blame shedding on the pets. Humans are prolific shedders, with
about 600,000 particles of skin flaking off every hour. By age 70,
humans lose an average of 105
pounds of skin.


Alaska is home to a type of frog that allows itself to freeze every year.
The wood
frog turns two-thirds of its body water into ice then, in spring,
thaws out and keeps on hopping.


In seahorses,
it’s the male who gets pregnant and gives birth. The female seahorse
deposits her eggs inside the male, who fertilizes and carries them
inside a pouch until they’re ready to be born.


The most prolific mom of all time was Feodor
Vassilyev, who had 69 children. She gave birth to 16 pairs of
twins, seven sets of triplets and four sets of quadruplets.


has indicated that hearing, if you still have it, is the last sense to go when you die.


Your ears may still pick up sound after you die, but every muscle
in your body relaxes at the time of death, including those that control the bowels.
This sometimes results in a final bowel movement post-death.


All this talk of death might be giving you goosebumps, but did you know you can get goose bumps when you’re dead?
Rigor mortis is a stiffening of the muscles and it can cause a goose
bump-like appearance on the skin of a corpse.


Let’s talk about something more hopeful. Scientists figured out how
to turn peanut butter into diamonds.
All they need is a higher pressure than what you’ll find at the
center of the earth. Easy, right?


suspect that fish communicate through the noise of their farts – just like some teenage boys …


In 2008, a 13-year-old boy was arrested for farting
too much in school. The sheriff’s office said he “continually
disrupted his classroom environment” with intentional


Tuned_In / istockphoto


can get PTSD and depression. A study confirmed the presence of
anxiety and mood disorders in chimpanzees and raised ethical
questions about using them for experimentation and captivity.


(commonly called killer whales) also show signs of stress when placed
in captivity. This ranges from dorsal fin collapse to attacking and
killing humans, something they don’t do in the wild.

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 A hotel in Bolivia is made
of salt. That includes the chairs, tables and beds.


Hotel De Sal Luna Salada


For something sweeter, look no farther than San Francisco, where an
artist created an entire room out of cake.


Spoke Art


In 1992, Singapore banned chewing
gum. This fell in line with the country’s strict laws against
litter, graffiti, jaywalking, spitting and other untidy habits.


Hell can freeze over – and does all the time. Hell,
Norway, that is. The town of Hell is a tiny village that reaches
temperatures as low as -13 degrees every winter. There are at least three other towns in the world named Hell, including one in Michigan, one in the Netherlands (both of which also freeze) and another in the Cayman Islands (that doesn’t).


A man in India married
a dog in order to beat a curse he earned by attacking a pair of
dogs years earlier.


Before modern erasers, artists and others had to use rolled up white
to remove pencil marks.


The man behind the Richter scale, Charles
Richter, was quite the character. Along with being a poet,
Trekkie and backpacker, he was an avid nudist. That should shake
things up.


public domain


Today, we know Listerine
for keeping our mouths minty fresh. But it has been sold in the past
as a cure for dandruff, a surgical disinfectant, a floor cleaner, a
hair tonic and a deodorant.


honey bees only mate once. As he finishes, the male bee’s
endophallus is ripped from his body, his abdomen tears open and the
bee dies. Ain’t love grand?


If that made you want to steer clear of romance, you’re not alone.
is the fear of love or of becoming emotionally connected with another
person. Yep, it’s a real thing.


Nintendo briefly got into the love game. In the ’60s the
entertainment company owned a love
hotel in Japan, where such hotels are basically rooms for rent by
the hour, complete with fanciful themes, costumes, “toys,”
food and more.


Next time you’re suffering from a hangover, look no further than
for the cure. A team of scientists found Sprite relieved hangover
symptoms better than many other drinks and cures.


In ancient Rome beauty masks had an interesting ingredient
list that included things like placenta, excrement, sulfur, sweat
from sheep’s wool, animal urine, ground oyster shells and bile.


IanaChyrva / istockphoto


Belarusian dictator Alexander Lukashenko outlawed clapping after his
opposition started using it as a form of dissent. People were
actually arrested for clapping, including Konstantin
Kaplin, who has one arm.


There is a house in Rockport, Massachusetts, made of newspaper, including paper furniture such as a piano, a desk and a chair.


 In 2011, NASA discovered “Y-dwarfs,”
stars that are even cooler than the human body.


A large sinkhole off the coast of Belize called the Great
Belize Blue Hole
is a staggering 410 feet deep. It is the deepest known natural sinkhole of its kind.


Just south of Mexico City is the Island
of Dolls, home to hundreds of terrifying dolls with missing eyes,
limbs and heads. It was originally meant as a dedication to a little
girl who died under strange circumstances.


Turns out it’s the tail. A kangaroo
can’t hop if its tail is off the ground.


Here’s a bonus kangaroo
fact: Whether their tail is on the ground or not, they can’t hop


Newton never married and it’s believed he died a virgin.


A man was arrested for
being naked – in his own home. Police said he was arrested
because someone saw and reported him and “officers believed he
wanted to be seen naked by the public.”


Hippos nurse their babies with bright
pink milk
. Special acids the hippo secretes account for the
unique color.


The stoic philosopher Chrysippus
is one of the few people who have actually died of laughter. The
story goes that he saw a donkey eating figs and yelled, “Now
give the donkey a pure wine to wash down the figs!” He then died
laughing at his own joke.


public domain


is the fear that somewhere in the world a duck or goose is watching


Sonsedska / istockphoto


When the Mona Lisa was stolen from the Louvre in 1911, Pablo
was one of the suspects.


Just about every piece of plastic
ever made still exists in some form, as the material takes 500-1,000
years to degrade.


A lot of that plastic has ended up in the ocean,
unfortunately. About 90% of trash on the ocean’s surface is plastic.
That means about 46,000 pieces of plastic for every square mile of


The Incas held the humble potato
in high esteem. They could preserve them as a mash for up to 10 years
and also used them to treat injuries and aid in childbirth.


Vatican City,
home of the Catholic church, has the highest crime rate in the world.
This is likely due to its small population and high rate of tourism.


was one of the most powerful pirate lords of all time,
rising up from a prostitute to the commander of the Red Flag Fleet, a
coalition of more than 600 ships and 50,000-70,000 pirates.

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Thai police who step out of line are forced to wear a pink Hello


are sharper than we give them credit for. A team of researchers found
that they could train sheep to recognize human faces in photographs.


When the game Twister
came out it got more than one person’s knickers in a twist.
Milton-Bradley published the game, with trepidation, and one of their
competitors quickly accused them of selling  “the deed in a box.”


Every May, indigenous communities in the Bolivian Andes celebrate
a festival of violent fist fights that lasts several days.


Just in case regular surfing wasn’t extreme enough, some folks have
started “volcano
surfing,” rocketing down the slopes of volcanoes at speeds
as high as 56 mph.


Featured Image Credit: vojce / iStock.