More than two years ago, scientists found a mysterious “golden orb” two miles below the ocean’s surface in the Gulf of Alaska. Since then, they have been trying to figure out what it is. Could it be an egg of some sea creature? A species of sponge never seen before? Some other new organism? At last, they have an answer, but the discovery emphasized just how much people have to learn about the ocean’s depths.  

The golden orb was initially attached to a rocky outcropping at 2 miles deep. Researchers aboard a 2023 deep-sea expedition of the National Oceanic and Atmospheric Administration collected a sample using a remotely operated vehicle, but they were unable to identify it. They sent it to the Smithsonian National Museum of Natural History, where a team with expertise in genetics, deep sea biology, and animal structures worked to solve the puzzle.  

The object didn’t have normal animal anatomy, but its surface was covered in stinging cells called cnidocytes, commonly found on corals and anemones. Then one scientist recognized that the cnidocytes were a specific type called spirocysts. Spirocysts are only found in a class of corals and anemones called Hexacorallia, so the researchers compared the golden orb to another Hexacorallia specimen found in 2016. The spirocysts looked similar, but a genetic comparison could confirm that.  

Their first attempts to analyze the organism’s DNA did not reveal firm answers, probably because DNA from other organisms contaminated the sample. But further testing confirmed that the golden orb’s DNA was nearly identical to that of the 2016 Hexacorallia, a deep-sea anemone called Relicanthus daphneae. Scientists hadn’t recognized it because the orb was only part of the base of the anemone that attaches to rock. It took two and a half years and a team of scientists, but they solved the mystery of the golden orb at last. 

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Bull sharks have some of the highest levels of testosterone in the animal kingdom and a reputation for being among the most aggressive of all sharks. Until recently, scientists also thought they lived fairly solitary lives. In reality, though, bull sharks aren’t loners at all. They have surprisingly complex social networks, including “friends” they prefer and other sharks they avoid.

Researchers spent six years tracking 184 bull sharks in the Shark Reef Marine Reserve in Fiji, observing them for more than 136 hours during hundreds of dives. The sharks fell into three age groups: nearly-adults who were not yet sexually mature, sexually mature adults, and older adults who were past their reproductive age. The scientists considered sharks to be “associating” if they stayed within one body length of each other, and they identified several behaviors indicating different relationships. Some sharks swam side by side while others led or followed another shark or yielded to a passing shark. For example, two male sharks, named Big Poppa and Sharkbite, sometimes swam parallel to one another or engaged in a lead-follow behavior. 

Middle-aged adult sharks were the most socially connected, and they spent more time with sharks around the same size as they were. Older sharks generally got less social as they aged. Male and female sharks both spent more time with other females, yet males had slightly more overall social connections than females did. Much like humans, some bull sharks were social butterflies, while others had far fewer associations. Also like humans, some bull sharks intentionally avoided certain individuals. Since Fiji’s shark reserve is an ecotourism site, it’s unclear how much this social networking reflects bull shark behavior elsewhere or why it occurs. What is clear is that bull sharks have far more elaborate social lives than scientists ever realized.

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People use mirrors for grooming activities like shaving, washing their face, and applying makeup. Under the sea, though, hundreds of marine fish rely on cleaner wrasses to groom them. These little fish eat parasites and dead tissue from the skin of larger fish at “cleaning stations.” Now it turns out those cleaner fish understand how to use mirrors too, when given the opportunity! 

 A few years ago, scientists in Japan demonstrated that cleaner wrasses can recognize themselves in photos and mirrors. In those experiments, the fish did not attack photos showing their own face (even with their face edited onto an unfamiliar body), but they did attack photos of a cleaner wrasse that had an unfamiliar face—even when that face was photoshopped onto their own body. Those experiments also confirmed that the fish knew the photo was of themselves. When the photo included a mark on their throat that looked like a parasite, the fish tried to rub their throat to get rid of the parasite. They didn’t do that when shown an unfamiliar fish’s face having a parasite mark.

In a new study, the same scientists continued testing how cleaner wrasses interact with mirrors. They gave the fish a mark that looked like a parasite and then put a mirror in the tank. Within an hour, the fish used the mirror to find and rub off the fake parasite. But after several days with the mirror, they did something more surprising: the fish picked up a piece of shrimp from the tank floor and dropped it in front of the mirror, tracking its movement in the reflection as it fell to test how the mirror worked. This kind of behavior, which has been observed in manta rays and bottlenose dolphins, shows a level of self-awareness that people didn’t know cleaner wrasses had. It also suggests that many more animals have self-awareness than people realized!

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It’s easy to take bacteria for granted when these single-celled creatures are too small to see with the naked eye. Yet bacteria are the most plentiful living organisms on earth and play a huge role in maintaining ecosystems. The population of one group, called SAR11, in the world’s oceans is estimated to be around 24,000,000,000,000,000,000,000,000,000! (That’s 27 zeros.) SAR11 bacteria make up about 20% to 40% of plankton cells in upper layers of the ocean.

Scientists have learned that the very characteristic that’s helped these bacteria survive so well also makes them extra sensitive to unexpected changes in the world’s oceans. So far, the secret to SAR11’s evolutionary success has been their ability to adapt to environments with very few nutrients. They do this by getting rid of genes they don’t need. This helps them conserve energy when food is scarce. When scientists recently looked at the genes of hundreds of these bacteria, they learned which genes tended to be lost. The missing genes were the ones that regulate the cell cycle and ensure that cell division and replication of DNA occurs normally. The strategy of losing those genes is effective if the surrounding environment remains fairly stable. But oceans have been in a state of ongoing flux in recent years due to effects of shifts in the global climate on ocean temperature and pH levels.

Under that stress, these bacteria are replicating DNA without dividing properly. They end up with extra chromosomes and then grow too big and die—even when nutrients become more abundant. That’s bad news for more than just SAR11. These bacteria are important in regulating marine food webs, so environmental instability affecting them could have far-reaching consequences for many other creatures. Learning more about this vulnerability can help scientists understand what to expect as conditions in the oceans change.

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Beaked whales are among the hardest whale species to find because they dive deeper than any other mammal (some reaching almost 10,000 feet deep), they only surface for a couple minutes at a time, and are especially wary of boats. But knowing where they live is important so the military can avoid going there for sonar exercises, which hinder the whales’ feeding and can cause severe injury. After five years of searching, scientists finally found the species for the first time in the open sea—and an albatross nearly sabotaged the whole operation.

Along the coast of Baja California, Mexico in June 2024, scientists spotted a small group of ginkgo-toothed beaked whales swimming. This rare species was initially described in 1958, when a pair of Japanese scientists found one stranded on a beach near Tokyo. Since then, fewer than two dozen have been identified, always stranded on beaches.

The recent search began in 2020 when scientists started tracking a group of whales making a call not associated with any other species. The biologists named the call BW43 and returned to the area where they heard the call every year for three years. But each time, they lacked the specialized equipment that would ultimately help them find the ginkgo-toothed beaked whales.

When they returned last summer, they were aboard a research vessel with a collection of underwater microphones and high-powered binoculars. When a pair of beaked whales they had been following surfaced, they shot a small arrow that nicked a tiny piece of skin from one—which an albatross nearly stole before they could pull it aboard. Shouting and a few tossed bread rolls helped the crew chase off the bird long enough to pull in the sample and test its DNA, confirming they had, in fact, found the elusive ginkgo-toothed beaked whales.

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You’ve heard of the Death Star weapon in Star Wars, but have you heard of the carnivorous death ball sponge in the South Atlantic Ocean? The predatory sponge is one of 30 new species that scientists discovered on an expedition around Antarctica—and there are likely more new species to come. Scientists on board the Schmidt Ocean Institute’s research vessel Falkor (too) collected nearly 2,000 specimens from 14 different animal groups while looking for new species in the South Sandwich Islands. This group of volcanic islands sits in the South Atlantic Ocean about 1,000 miles east of the southern tip of South America and about 1,100 miles northeast of the Antarctic Peninsula.

So far, the scientists have evaluated less than 30% of the samples they collected. It will take time to examine and identify the rest, including whether they are an entirely new species or variations of known species. For example, they also collected “zombie worms,” from the genus Osedax, which researchers have seen before. These worms don’t have a mouth or gut. Instead, they secrete acid to “drill” into and absorb fats from animal bones, such as whale carcasses. Symbiotic bacteria living in the worms break down these fats, providing nutrients the worms can absorb.

The “death ball sponge” was found at 3,600 meters—more than two miles deep—at a trench near Montagu Island. Scientists are currently calling it Chondrocladia sp. nov. because it looks like some known species of the genus Chondrocladia, but the “sp. nov.” stands for “species nova,” or “new species.” Although it does not yet have a species name, researchers have concluded that it’s a predator, based on the tiny hooks that cover large white spheres on stalks extending from the sponge. Imagine multiple round lollipops sticking out from a sponge anchored to the ocean floor, except licking these lollipops would be like licking a cactus.

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So much of the ocean remains undiscovered because it is so difficult to reach, but the sea revealed more of its secrets in July 2017, when an iceberg nearly the size of Delaware broke away from a large ice shelf off the coast of Antarctica’s Weddell Sea. The slab of ice, about 2,239 square miles in size, separated from the Larsen C Ice Shelf in the Graham Land peninsula of Antarctica and left exposed a seabed previously hidden under 650 feet of ice.

Researchers sent a remotely operated vehicle named Lassie to explore the area in early 2019. When they discovered more than 1,000 dimples in the ocean floor, they were baffled at first. The dimples were not randomly scattered but were instead arranged in clear patterns. Some were shaped like a crescent, others like an oval, others in a line, and others in a sharp U-shape.

Scientists on board the research vessel debated what the dimples could be and added up the clues—their size, their shape, and knowledge of local sea life. They concluded the dimples were nests of yellowfin rockcod. Male yellowfin rockcod guard nests and their surrounding area for four months after females lay eggs, so the vast neighborhood of clustered nests likely enabled a network of guards to keep the eggs safe. Scientists suspect isolated nests on the outer edges were guarded by larger, stronger fish that could defend the area alone. About one in seven nests had pebbles in or around them, on which biologists think the fish laid their eggs to prevent rotting on the floor or predation from animals in the mud. Closer investigation also revealed that 72 of the 1,036 nests still contained larvae.

Discovery of this unexpected nursery area underneath an ice shelf supports the idea of establishing a protected area in the Weddell Sea to keep future generations of yellowfin rockcod safe.

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The ocean can be a dangerous place for juvenile fish, but researchers recently discovered a way some of them ward off predators—carrying around a baby. A baby anemone, that is. Divers off the coasts of Palm Beach, Florida and Tahiti have photographed evidence of a particular kind of symbiotic relationship between young fish and larval anemones. Symbiotic relationships are ones where at least one species benefits from the activity. In a mutualistic relationship, like this one, both benefit. In this case, the juvenile fish receives protection from becoming another fish’s dinner, and the anemone gets a free ride far beyond its birthplace.

Researchers used blackwater photography—a technique of taking photos in the open ocean at night—to snap pictures of filefish, driftfish, pomfrets, and a young jack swimming around with larval anemones in their mouths. Anemones are already part of a well-known mutualistic partnership with clownfish, which shelter in grown anemones, eat their leftover food scraps while keeping the anemones free of parasites, and circulate water around them. In this newly discovered relationship, the mutualism is short-term but has potentially long-term ramifications for anemone populations. Larval anemones can only travel so far on their own, but being carried further afield by fish means expanding their range.

The small fish, meanwhile, carry the anemone almost like a defensive shield; anemones pack a nasty sting that predators would likely want to avoid. The sting might not kill a fish that tries to take a bite, but it’s a far less tempting meal. The exciting discovery has now raised more questions for scientists to explore: How far and how long do the fish carry the anemone? Do they swap them out? How many anemones survive the trip? What exactly triggers fish to pick up anemones in the first place? Only further study may reveal some of these answers.

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For years, few scientists have devoted much time to studying Arctic diatoms, single-celled algae enclosed within a wall of glass-like silica. These bizarre organisms, after all, appeared frozen in the sea ice, stuck in dormancy, or so many scientists believed. In reality, however, ice diatoms are quite active—skating along the ice at temperatures as low 5ºF (-15ºC). That’s what scientists recently discovered when they collected diatoms from the Arctic during an expedition in the Chukchi Sea, the body of water that sits between Alaska and Siberia above the Bering Strait, and brought them back to their lab to study them.

Back at their lab, the researchers introduced the specimens to ice that resembled the diatoms’ natural environment. Then they watched as the diatoms sped along tiny channels in the ice. The algal cells glided along without the use of any appendages and without the kind of movement, such as wiggling, that other limbless organisms might use. The diatoms do it by secreting mucus that sticks to the icy surface at one end, creating a sort of anchored rope that they can pull themselves along. What stunned the researchers, though, was that the ice diatoms could move in this way at such cold temperatures. No other diatoms or other single-celled plants or animals had been documented as moving at temperatures this low.

Now the researchers are working to understand how diatoms function at such cold temperatures and, even more importantly, how they fit into the broader ecosystem of the Arctic. With the long-term existence of Arctic ice threatened by a warming global climate, researchers want to know: What will happen when the diatoms’ icy highways are gone?

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Dental offices and beauty salons follow strict hygiene and sanitation guidelines to prevent the spread of germs among people coming in for a teeth cleaning or eyebrow wax. But the same rules don’t apply to the “beauty salons” and mouth cleaning stations under the sea—and that may be a good thing.

Over 200 different species of fish and over 50 different shrimp species serve the vital role of cleaners to their fellow underwater residents. These cleaner fish often gather in “cleaning stations” on coral reefs where larger fish visit to have parasites and bacteria picked out of their mouths and off their scales. Scientists have known about this for many years, but only recently have they begun exploring what role these cleaning behaviors might play in moving microbes around the reef ecosystem.

To begin understanding this role better, researchers recently studied the impact of the cleaning goby. These fish are only about two inches long and often called neon gobies because their long, slender bodies have an iridescent stripe of color running from their nose to their tail. Scientists removed cleaner gobies from cleaning stations on two reefs off the coasts of Puerto Rico and St. Croix. Then they compared the water nutrients, microbe communities, and fish behavior of these reefs with nearby reefs that still had cleaning gobies. It turned out more fish visited the sites with cleaner gobies, and the variety of both microbes and nutrients differed between the sites.

Further research will help the scientists understand the significance of what they found to the broader health of marine environments, but one thing is clear: cleaner gobies do more than remove bacteria from individual fish. They play a big role in the microbe community of entire reef systems.

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