Posts Tagged ‘shark’

By Elizabeth Pennisi

Imagine having to wait a century to have sex. Such is the life of the Greenland shark—a 5-meter-long predator that may live more than 400 years, according to a new study, making it the longest lived vertebrate by at least a century. So it should come as no surprise that the females are not ready to reproduce until after they hit their 156th birthday.

The longevity of these sharks is “astonishing,” says Michael Oellermann, a cold-water physiologist at Loligo Systems in Viborg, Denmark, who was not involved with the work. That’s particularly true because oceans are quite dangerous places, he notes, where predators, food scarcity, and disease can strike at any time.

Greenland sharks (Somniosus microcephalus) had been rumored to be long-lived. In the 1930s, a fisheries biologist in Greenland tagged more than 400, only to discover that the sharks grow only about 1 centimeter a year—a sure sign that they’re in it for the long haul given how large they get. Yet scientists had been unable to figure out just how many years the sharks last.

Intrigued, marine biologist John Steffensen at the University of Copenhagen collected a piece of backbone from a Greenland shark captured in the North Atlantic, hoping it would have growth rings he could count to age the animal. He found none, so he consulted Jan Heinemeier, an expert in radiocarbon dating at Aarhus University in Denmark. Heinemeier suggested using the shark’s eye lenses instead. His aim was not to count growth rings, but instead to measure the various forms of carbon in the lenses, which can give clues to an animal’s age.

Then came the hard part. Steffensen and his graduate student Julius Nielsen spent several years collecting dead Greenland sharks, most of them accidently ensnared in trawling nets used to catch other types of fish. After that, they employed an unusual technique: They looked for high amounts of carbon-14, a heavy isotope left behind by nuclear bomb testing in the mid-1950s. Extra carbon from the resulting “bomb pulse” had infiltrated ocean ecosystems by the early 1960s, meaning that inert body parts formed during this time—in particular eye lenses—also have more of the heavy element. Using this technique, the researchers concluded that two of their sharks—both less than 2.2 meters long—were born after the 1960s. One other small shark was born right around 1963.

The team used these well-dated sharks as starting points for a growth curve that could estimate the ages of the other sharks based on their sizes. To do this, they started with the fact that newborn Greenland sharks are 42 centimeters long. They also relied on a technique researchers have long used to calculate the ages of sediments—say in an archaeological dig—based on both their radiocarbon dates and how far below the surface they happen to be. In this case, researchers correlated radiocarbon dates with shark length to calculate the age of their sharks. The oldest was 392 plus or minus 120 years, they reported in Science. That makes Greenland sharks the longest lived vertebrates on record by a huge margin; the next oldest is the bowhead whale, at 211 years old. And given the size of most pregnant females—close to 4 meters—they are at least 150 years old before they have young, the group estimates.

Oellermann is impressed not only with how old the sharks are, but also how Nielsen and his colleagues figured out their ages. “Who would have expected that nuclear bombs [one day] could help to determine the life span of marine sharks?” he asks.

He and others think cold water helps lengthen the animals’ lives by slowing down their growth and biochemical activity. “Lower metabolic rate plays a big role,” agrees Shawn Xu, a geneticist at the University of Michigan, Ann Arbor. “But that’s not the whole story.” Three years ago, his work in nematodes showed that cold can also activate antiaging genes that help an animal better fold proteins, get rid of DNA-damaging molecules, and even fight off infections more effectively, extending life span. The cold-activated molecules “are evolutionarily conserved” across the animal kingdom, and thus these pathways very likely exist in these sharks, too, he predicts.

Paul Butler isn’t surprised that frigid waters host such old creatures. In 2013, the sclerochronologist (a scientist who studies the growth of hard tissues in invertebrates) at Bangor University in the United Kingdom and his colleagues described a 500-year-old ocean quahog (Arctica islandica), a chowder clam found in the North Atlantic. Still, even though two multicentenarian species have turned up in the North Atlantic in just a few years, Butler is skeptical that there are many more out there awaiting discovery. “It won’t be that we won’t have more surprises,” he says, “but I regard these [two] as exceptions.”

http://www.sciencemag.org/news/2016/08/greenland-shark-may-live-400-years-smashing-longevity-record


A new study discovers sharks in Greenland can live up to be 400-years-old, making them the longest-living vertebrates on the planet.

by Traci Watson

The Greenland shark has long been belittled as sluggish, homely and dim-witted. But now the species can demand respect: scientists say it is the planet’s longest-lived vertebrate, or animal with a backbone.

Eight of 28 Greenland sharks profiled in a new study in today’s Science were 200 years or older, by scientists’ best estimates. One enormous female was aged at least 270 when she was caught – and she may well have been 390. That would make her possible birth date in the era of Rembrandt and Galileo.

Even the study’s authors were astonished by the results, which allow the humble Greenland shark to steal the longevity prize from the bowhead whale, the previous record-holding vertebrate. The oldest bowhead reached a mere 211 years.

The study turned up such mind-boggling ages that the scientists “kept checking the math,” says study author Peter Bushnell of Indiana University South Bend. “Typically nothing except for trees lives this long.”

The Greenland shark has all the hallmarks of an animal that survives to extreme old age, says Jelle Boonekamp of the Netherlands’ University of Groningen, who was not associated with the study. For starters, females can stretch 15 feet, which is longer than a station wagon. Those proportions mean the shark has few predators.

The Greenland also has a low metabolism, befitting the ultra-cold northern waters where it’s most often found. It putters along at less than half a mile per hour, “the tortoise of the undersea world,” says Chris Harvey-Clark of Canada’s Dalhousie University, who wasn’t part of the study.

The biggest sharks probably “don’t have to eat every day. They might just have a big meal once or twice a year,” hypothesizes study co-author Julius Nielsen of Denmark’s University of Copenhagen. That meal most often consists of seal or large fish, but the Greenland is not above gulping down carrion, from dead reindeer to chunks of moose.

To reveal the shark’s age, Nielsen and his colleagues studied the eyes of almost 30 Greenland sharks, nearly all caught accidentally by fishing boats or scientific surveys. A section of the shark’s lens forms when the animal is in utero. The researchers measured this section’s levels of radioactive carbon, a method often used to date archaeological samples, and extrapolated to the year the sharks were born.

Sharks of the same species can have different personalities, indicates a new study published in the Journal of Fish Biology.

The study, led by Dr. Evan Byrnes of Macquarie University in North Ryde, Australia, examined interindividual personality differences between Port Jackson sharks (Heterodontus portusjacksoni).

Trials were designed to test the sharks’ boldness, which is a measure of their propensity to take risks, but also an influencer of individual health through its correlation with stress hormones and associated physiological profiles.

Port Jackson sharks were first introduced to a tank where they were provided with shelter, and timed to see how long it took for each shark to emerge from their refuge box into a new environment.

The second behavior test exposed each shark to handling stress, similar to handling by a fisherman, before releasing them again and observing how quickly they recovered.

The results demonstrated that each shark’s behavior was consistent over repeated trials, indicating ingrained behaviors rather than chance reactions.

That is, some sharks were consistently bolder than others, and the sharks that were the most reactive to handling stress in the first trial were also the most reactive in a second trial.

“This work shows that we cannot think of all sharks as the same,” Dr. Byrnes said.

“Each has its own preferences and behaviors, and it is likely that these differences influence how individuals interact with their habitat and other species.”

“We are excited about these results because they demonstrate that sharks are not just mindless machines. Just like humans, each shark is an individual with its unique preferences and behaviors,” said co-author Dr. Culum Brown, also from Macquarie University.

“Our results raise a number of questions about individual variation in the behavior of top predators and the ecological and management implications this may have. If each shark is an individual and doing its own thing, then clearly managing shark populations is much more complicated than we previously thought.”

“Understanding how personality influences variation in shark behavior – such as prey choice, habitat use and activity levels – is critical to better managing these top predators that play important ecological roles in marine ecosystems.”

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E.E. Byrnes & C. Brown. Individual personality differences in Port Jackson sharks Heterodontus portusjacksoni. Journal of Fish Biology, published online May 26, 2016; doi: 10.1111/jfb.12993


By Henry Hanks

It’s not often that someone discovers a new species, especially when it’s been under their nose for years.

A shark collected during a research expedition in 2010 turns out to be a ninja lanternshark, a brand new species of shark, so named because it is all black, which is how a ninja is typically dressed.

The scientific name is Etmopterus benchleyi, a reference to “Jaws” author Peter Benchley.

Grad student Vicky Vasquez and Dr. Douglas J. Long wrote about their findings after being asked to take a closer look at the shark (along with her professor, Dr. David A. Ebert of the Pacific Shark Research Center at Cal State).

“It is also the first lanternshark to ever be discovered off of the central eastern Pacific Ocean near Central America,” Vasquez pointed o

Four children, ages 8 to 14 years old, decided upon the name “ninja lanternshark.”

http://www.cnn.com/2015/12/24/us/shark-discovery-feat/index.html

Over the past nine months, deaths have been reported from being electrocuted, falling from bridges, and running with bulls—all while attempting to capture an outrageous selfie. Now, following the most recent news of a Japanese tourist who fell to his death after trying to pose for a picture at the Taj Mahal’s Royal Gate in India, media website Mashable investigated just how many accidents like this have taken place over the last year, and compared that to the number of shark-related deaths.

Their findings: since the beginning of the year, 12 people have died while attempting to take selfies, while only eight people died following a shark attack. Mashable also pointed out that only four of the selfie fatalities occurred from falling; others died after being struck by trains, for example, and a Texas teenager recently died from accidentally shooting himself while posing for a selfie with a gun.

Back in January, two men were killed in Russia after posing for a selfie with a hand grenade, according to Al Jazeera, prompting the Russian police to launch a “safe selfie” campaign. And other tourist attractions—including Disneyland!—have banned selfies or selfie-sticks entirely, citing safety concerns. Selfie-related injuries and deaths even has its own Wikipedia page.

http://news.health.com/2015/09/24/selfie-shark-attack-deaths-mashable/

Brennan Phillips and some colleagues were recently on an expedition to Kavachi volcano, an active underwater volcano near the Solomon Islands in the South Pacific. But they weren’t prepared for what they saw deep inside the volcanic crater:

Sharks!

Hammerheads and silky sharks, to be specific, contentedly swimming around despite the sizzling water temperatures and biting acidity.

Volcanic vents such as these can release fluids above 800 degrees Fahrenheit and have a similar acidity to vinegar, according to the Marine Education Society of Australasia.

“The idea of there being large animals like sharks hanging out and living inside the caldera of the volcano conflicts with what we know about Kavachi, which is that it erupts,” Phillips, a biological oceanography Ph.D. student at the University of Rhode Island.

This brings up some perplexing questions about what the animals do if the volcano decides to wake up:

“Do they leave?” Phillips asks. “Do they have some sign that it’s about to erupt? Do they blow up sky-high in little bits?”

The volcano wasn’t erupting when Phillips’ team arrived, meaning it was safe to drop an 80-pound camera into the water to take a look around. After about an hour of recording, the team fished the camera out and watched the video.

First, the video showed some jellyfish, snappers, and small fish. Then, a hammerhead swam into view, and the scientists erupted in cheers. They also saw a cool-looking stingray.

http://www.businessinsider.com/sharks-found-swimming-near-active-underwater-volcano-2015-7

To understand why so many people are drawn to deadly creatures of the deep, look to the quote by the sociobiologist E.O. Wilson: “We are not afraid of predators, we’re transfixed by them … We love our monsters.”

The best example of this paradox: Even as shark attacks have spiked off the coast of the Carolinas this year, Discovery Channel’s Shark Week kicked off this weekend with the most programming hours in its history. People should be at least a little afraid of sharks, it seems, yet they can’t get enough of them.

Perhaps that explains why surfers brave shark-invested waters again and again in search of the perfect wave—and suffer some of the most gruesome shark attacks as a result. After hearing about a rash of shark attacks—five of them fatal—in Western Australia a few years ago, the kitesurfer and entrepreneur Hamish Jolly began exploring ways to protect ocean-sport enthusiasts without forcing them to get out of the water.

In a 2013 TedxPerth talk, Jolly presented the results of his research: a series of striped wetsuits that aim to confuse and deter sharks, leaving the surfer within the suit (hopefully) unharmed.

Together with the University of Western Australia neurobiologist Nathan Hart and the industrial designer Ray Smith, Jolly found that a suit with a dark panel and striped arms and legs would be best for surfers, since near the surface of the water, “being backlit and providing a silhouette is problematic,” he says. The design also makes the surfer look like a lionfish or sea eel, which sharks usually don’t eat. For SCUBA diving, Jolly’s team crafted a blue wetsuit that aims to hide the diver within the water.

In an test depicted in the Ted video above, the striped pattern seems to work when using a non-human bait. While the shark quickly attacked a rig covered in standard, black neoprene, it simply brushed past the zebra-striped canister. Human testing is “ongoing,” Jolly notes.

Other researchers haven’t been quite so bullish about the invention. In addition to sight, sharks use other senses, like smell and hearing, to find their prey.

George Burgess, the director of the Florida Program for Shark Research, told National Geographic that the striped pattern might be even more tempting than a standard wetsuit design. “That striped suit that is supposed to look like a lionfish is about as nice a thing as you can do to attract a shark, because of the contrast between dark and light,” he said.

Jolly’s company, Shark Attack Mitigation Systems (SAMS), is selling the suits for about $440, which might be a small price to pay for finishing a surfing trip with all your limbs intact. Still, a prominent caution page reads, “It is impossible for SAMS to guarantee that 100 percent of sharks will be deterred under all circumstances with the SAMS technology.” And that’s not necessarily SAMS’ fault, it suggests: “All sharks are dangerous and unpredictable creatures.”

http://www.theatlantic.com/technology/archive/2015/07/shark-attack-wetsuit/397772/?utm_source=SFFB