Tag Archives: shark

Great White sharks may mistake humans for seals, explaining attacks

Shark attacks are exceedingly rare when you consider the sheer number of beachgoers that cross paths with these apex predators. Every year, there are no more than a couple dozen unprovoked shark attacks with an annual average of just four unprovoked fatalities. While every death is a tragedy, it’s worth bearing in mind that three times more people are killed by vending machines and about 30 times more are killed by falling coconuts than sharks.

What’s more, on the very rare occasion that sharks attack people, it may all be due to a case of mistaken identity. According to researchers from Australia, sharks can’t see very well, so they may not be able to distinguish swimmers at the water’s surface from their natural prey. In other words, sometimes humans just happen to look like their usual food.

Mistaken identity

This insight was gained after researchers looked at various silhouettes from the shark’s point of view. They recorded and compared video footage of swimmers, people paddling surfboards, and seals as a shark would see them from right below the water, with sunlight in the background.

“Surfers are the highest-risk group for fatal shark bites, especially by juvenile white sharks,” says lead author Dr. Laura Ryan, a post-doctoral researcher in animal sensory systems at Macquarie University’s Neurobiology Lab.

In order to truly put themselves in the sharks’ fins, the researchers employed their knowledge of the great whites’ retinal structure and brain visual systems to estimate their visual acuity. The focus was on the retina of great white juveniles, which are responsible for the majority of attacks on humans. These young sharks tend to have poorer vision than adults and are also more likely to venture inside habitats frequented by humans.

The footage was fed into modeling programs to simulate the way a paddling human or swimming seal might look through the eyes of a shark. “I didn’t realize being a scientist would involve quite so much coding,” Ryan said, which reminds us that modern science is becoming increasingly interdisciplinary and coding has become a must-have skill in any researchers’ toolkit, regardless of their field.

The analysis suggests that sharks, which are believed to be color blind, are ill-equipped to tell apart the silhouette shapes of humans or their motion cues from those of seals. As the sharks grow larger, their retinas also improve. Experience may also help adults better tell apart seals from humans, learning what’s good or bad to eat as they age, the researchers claim in their study published in the journal Royal Society Interface.

“We found that surfers, swimmers and pinnipeds (seals and sea-lions) on the surface of the ocean will look the same to a white shark looking up from below, because these sharks can’t see fine details or colors,” Ryan said.

It’s not sharks’ fault we look like food

These findings confirm a long-standing theory that great whites and other sharks responsible for rare attacks on humans do not actively seek us as prey.

Unfortunately for sharks, they have a bad rep due to their fierce appearance and skewed portrayals in popular media (i.e. Jaws films). Meanwhile, humans kill millions of sharks every year for their fins, cartilage, and oil. And our fear of sharks has also led to the widespread installation of shark nets and drumlines, which further threaten sharks, as well as other marine life. Great whites are now classed as endangered.

Shark teeth found in Antarctica unlock mystery of Earth’s ancient climate cooling

The Eocene was the hottest period in the past 50 million years. With temperatures some 13 °C hotter than today, no ice around the poles, and mammals just starting to take over the world, our planet was a very different environment. But something weird happened. Some 50 million years ago, the climate transitioned from a “greenhouse” to cooler “icehouse” conditions, which impacted the evolutionary history of flora and fauna. 

Teeth from an ancient shark could now help us understand what happened.

Image credit: Flickr/ NOAA

Researchers have worked on several theories about what drove this climate shift, some focusing on Antarctica due to its contiguity to tectonic gateways and amplified temperature effects at high latitudes. The tectonic theory notes that as the Australian and Antarctic tectonic plates were spreading apart, this produced increased volcanism and CO2 emissions.

The Antarctic also played a key role in the eventual cooling — once the oceans around it began to freeze, Antarctic waters sent cold water and icefloes There’s evidence, for example, that the Drake Passage and the Tasman Gateway (two now-icy passages around the Antarctic) widened and deepened during this time.

The wider and deeper passages would have been necessary for the waters of the major oceans to come together and the Antarctic Circumpolar Current to form, studies showed. That current, which currently flows around Antarctica, traps cold waters in the Southern Ocean, keeping Antarctica cold and frozen.

In a new study, researchers from the University of California analyzed the chemistry preserved in the teeth of the now-extinct sand tiger shark species Striatolamia macrota. The shark used to hunt in the waters off the Antarctic Peninsula tens of million years ago and left well-preserved fossil teeth in what’s now Seymour Island. 

“By studying the chemistry preserved in these shark teeth, my colleagues and I found evidence of when the Drake Passage opened, which allowed the waters of the Pacific and Atlantic oceans to mix, and what the water felt like at the time,” lead author Sora Kim wrote in a commentary. “The temperatures recorded in shark teeth are some of the warmest for Antarctic waters.”

Teeth filled with information

For the study, the researchers studied 400 teeth from Seymour Island from all ages of sharks, which lived between 45 million to 37 million years ago. 

Illustrations of sand tiger shark teeth used by the scientists. Image credits: Christina Spence Morgan

Sand tiger sharks have sharp teeth that protrude from their jaw to grasp prey. They have hundreds of teeth on multiple rows, and over a lifetime, they shed and regrow thousands of teeth. Each tooth contains important environmental information, which is encoded within its chemistry and preserved there over millions of years. Essentially, a tooth can serve as a proxy, telling researchers information about the waters in which it was formed.

The outer layer of the teeth is formed by an enamel-like layer, with oxygen atoms from the water the shark lived in. The researchers analyzed the oxygen to determine the temperature and salinity of the water and found that the Antarctic waters stayed warmer than previously estimated

“It’s possible the difference was between waters closer to the surface and deeper on the sea floor, or the sharks whose teeth we found may have spent part of their lives in South America,” Kim wrote. 

The modern-day analog of sand tiger sharks spends summer and early fall between coastal Massachusetts and Delaware. When the waters cool off, they migrate to North Carolina and Florida. The researchers believe that ancient sand tiger sharks also migrated when Antarctic waters cooled off, heading north to warmer waters.

Carbon dioxide concentrations in the teeth were 3-6 higher than today, which indicates the atmospheric levels of C02 were also much higher than they are today — which fits with an overall higher temperature.

Another finding came from the element neodymium, which adsorbs and replaces other elements in the outer enamel-like material of the tooth during early fossilization. Its analysis provided the researchers with the earliest chemical evidence of water flowing through the Drake Passage, which aligns with existing tectonic evidence. If conditions are stable, the neodymium would remain stable through the years, but if the neodymium composition does change, it means that there are changes in oceanography.

“The early timing of the Drake Passage opening, but the delayed cooling effect, indicates there are complex interactions between Earth’s systems that affect climate change,” Kim wrote.

Ultimately, although the sand tiger sharks went extinct, other relatives managed to adapt to the changing conditions. However, the current climate events are different from the ones in the Eocene, because they happen much faster and leave less time for adaption. In addition, the current events are also coupled with other stressors, like pollution and shrinking ecosystems.

The study was published in the journal Advance Earth and Space Science

Fossil Friday: 300 million-year-old “Godzilla Shark” from New Mexico finally gets an official name

A press release from the New Mexico Museum of Natural History and Science (NMMNHS) on Thursday announces, at long last, the scientific name of this impressive shark.

The fossil and a 3D reconstruction of the animal’s skeleton. Image credits Jesse Pruitt / New Mexico Museum Of Natural History & Science.

First discovered eight years ago, the species has so far been known by an unofficial (if cool) name: the “Godzilla Shark”. But researchers are now confident enough in their observations to place the animal on the tree of life, and with that, give it its official scientific name. The animal lived around 300 million years ago, during the Carboniferous period.

Big shark

The shark, uncovered in the Manzano Mountains of New Mexico, has been named Dracopristis hoffmanorum. It’s part of an ancient lineage that split off from the main family, but one which did not stand the test of time. It’s unofficial names include “Godzilla Shark” and “Hoffman’s Dragon Shark” in recognition of its big jaws, large spine, and in honor of the Hoffman family who own the land where the fossil was found.

“Dracopristis and other ctenacanth sharks represent a unique evolutionary branch of the sharks that split off from the modern sharks and rays approximately 390 million years ago, but that went extinct by the end of the Paleozoic Era, about 252 million years ago,” the museum explained in the release.

Judging from the fossils, the animal could grow to around 6.7 feet in length. It had 12 rows of teeth growing out from powerful jaws, and two large fin spines on its back that could reach an estimated 2.5 feet in length. These could have played a role as a defensive measure against predators, the team explains. The animal was most likely an ambush predator, lurking in shallow lagoons and estuaries where it would surprise prey like crustaceans, fish, and anything else it could find, with a tooth-lined maw.

Dracopristis was discovered by accident, when John-Paul Hodnett, a paleontologist at the Maryland National Capital Parks was poking through some limestone fragments with his knife in the Manzano Mountains to sift through them. “At first, I thought what was flipped over was the cross-section of a limb bone, which was exciting as no large tetrapod had been found at that site before,” Hodnett explains.

Still, a day later, Hodnett and his team were convinced that the discovery was in fact a new species of fish, most likely from the genus Ctenacanthus, which is today extinct. It eventually turned out to be the most complete ctenacanth ever discovered in the whole of North America.

The last seven years were spent studying the fossil, which included preparation and digital scanning at the NMMNHS’s labs. This allowed the team to describe the new fossil and identify its place in the tree of life.

The paper “Ctenacanthiform Sharks From The Late Pennsylvanian (Missourian) Tinajas Member Of The Atrasado Formation, Central New Mexico” has been published in the Bulletin of the NMMNHS

Tech could save thousands of lives from shark bites over the next 50 years

Although fatal shark attacks are exceedingly rare, an increasing number of people are spending time in waters frequented by potentially dangerous sharks. Naturally, the number of shark attacks is thus expected to rise, unless people take preventive measures, such as employing electronic deterring devices.

According to a new study, the use of personal electronic deterrents could save the lives of up to 1,063 Australians along the country’s coastline over the next 50 years.

Credit: piqsels.

The researchers led by Professor Corey Bradshaw of Flinders University accessed the Australian Shark Attack File curated by Taronga Conservation Society Australia, which reported 985 shark attacks from 1900 to 2020 from 20 different species.

Using this data, the researchers developed a predictive model that estimates the preventive impact of electronic deterrents. These devices, such as the commercially available Shark Shield, produce a strong electric field that is designed to interfere with the shark’s electroreceptive system, a sense mediated by a network of sensors on the shark’s head.

Such devices are used by some professional divers but if more people used them, the likelihood of a shark bite would be reduced by 60%, said the researchers.

“Avoiding death, injury, and trauma from shark bites over the next half-century would be a realistic outcome if people use these personal electronic deterrents whenever they’re in the water, and as long as the technology is operating at capacity,” said Bradshaw in a statement.

“Given that governments are applying multiple approaches to mitigate shark bites such as drones, SMART drumlines, and acoustic monitoring, our simulations suggest electronic deterrents could make a valuable contribution to overall mitigation, and so help allay community fears.”

In their study, the researchers write that the cost of implementing electronic deterrence is greatly offset by the revenue gained from businesses that cater to water users and tourism.

Spatial distribution of shark-bite incidents in the Australian Shark Attack File. Red icons show incidents resulting in ahuman fatality. Credit: Professor Corey Bradshaw, Flinders University.

That being said, the authors also added that electronic deterrents aren’t perfect and people should be extra careful regardless of whether or not they use such devices.

“Although several studies have demonstrated that electronic deterrents can reduce the probability of shark bites, device efficacy varies among manufacturers and even between products of the same manufacturer,” said co-author Associate Professor Charlie Huveneers, who leads the Southern Shark Ecology Group at Flinders University.

“When testing these products scientifically, we need a large number of interactions to (i.e., using robust statistics) assess efficacy confidently. As a result, we often need to use bait or berley to attract sharks, which likely motivate sharks to bite more than in situations when sharks encounter a swimmer or surfer.”

The findings appeared in the journal Royal Society Open Science.

Overfishing is causing shark and ray populations to plummet

Populations of oceanic sharks and rays have crashed by more than 70% over the past half a century, and it’s our fault. The decline is mostly owed to overfishing, a new study shows — but conservation policies can help.

Image credit: Wikipedia Commons

The Union of Conservation of Nature (IUCN) has listed half of the world’s oceanic shark species as engendered or critically threatened. The giant manta ray is also endangered. Yet, this doesn’t seem to be nearly enough to protect these creatures.

Sharks and rays are landed for their meat, fins, gill plates, and liver oil, with catches increasing to an estimated peak of 63–273 million individuals in the early 2000s. The practice of shark finning, where sharks have their fins cut and then helplessly dumped back into the ocean, is still booming.

In the new study, researchers looked at data from 18 shark and ray species, measuring their abundance as well as their place on the list of threatened species. They created the first global census of sharks and rays and the results don’t look too good: there has been an overall 71% decline since 1970. The real situation could be even worse, because there isn’t sufficient data to look at trends back to 1950.

“What we’ve found is some really abundant animals that were really formerly highly abundant, wide-ranging, they’ve declined so steeply now they’re classified in some of the highest [extinction] threat categories,” Cassandra Rigby, one of the study’s authors, told ABC. “This jeopardizes the health of ocean ecosystems as well as food security in many poorer, developing nations.”

There were stark differences from area to area. In the Atlantic Ocean, following a long period of decline since 1970, populations began to stabilize at low levels after 2000. In the Pacific Ocean, abundances decreased steeply before 1990, and then declined at a slower rate. And in the Indian Ocean, shark abundances have declined steeply since 1970.

A thousand cuts — but one is particularly bad

The study showed sharks and rays can be affected by many factors such as climate crisis, oil and gas drilling, and ship strikes. But the main cause of decline has been by far overfishing. Proof of this is the twofold increase in fishing with longlines and seine nets, the gears used to catch oceanic sharks, during the past half-century, and the rapidly rising catch rates.

A previous study even estimated that an estimated 100 million sharks are killed by humans every year. This means between 6.4% and 7.9% of sharks of all species are killed annually, with little chance to replenish the population. The main culprit? The proliferation of shark finning to feed appetites for shark fin soup.

“We collate all information on all the threats as well — climate change, human disturbance. But in all of these 18 species the major threat really was fishing and harvesting,” said Rigby. “We aren’t protecting a vital part of our ocean ecosystems from overfishing, and this will lead to a continued decline in the health of our oceans.”

Rigby and her team highlighted some important improvements in conservation commitments in recent decades. Still, there’s a long way to go. Only a few countries impose catch limits specific to oceanic sharks, and fewer yet can demonstrate population rebuilding or sustainable fisheries for these species. Plus, obligations under wildlife treaties to restrict international trade of select species haven’t been well implemented.

Nevertheless, there are some encouraging findings, they noted. The white shark historically declined by an estimated 70% worldwide over the past half-century but is now recovering in several regions, aided by retention bans. Hammerhead shark populations are rebuilding in the Northwest Atlantic, thanks to stronger quotas in the US, and the blue shark is declining less than other species.

“It is possible to reverse shark population declines, even for slow-growing species, if precautionary, science-based management is implemented throughout the range of the species before depletion reaches a point of no return,” the researchers wrote.

The study has been published in the journal Nature.

Fossil Friday: ancient shark bones turn out to be the teeth of a new species of flying dinosaur

Researchers at the University of Portsmouth have made a lucky discovery in the collections of the Sedgwick Museum of Cambridge and the Booth Museum at Brighton: a new species of pterosaur.

The fossils as seen from different angles. Scale bar represents 10 mm. Image credits Author links open overlay Roy E. Smith et al., (2020), Proceedings of the Geologists’ Association.

The fossils have been part of these collections for almost 100 years now, being first uncovered between 1851 and 1900. They were found at the height of phosphate mining activity in the English Fens area. As was regularly the practice among workmen there at the time, they quietly sold any fossils they found to collectors for some extra money.

Before we judge them too harshly, it pays to keep in mind that they had a direct hand to play in the discovery of a new species, even if unwittingly. Since their discovery, the fossils were assumed to have belonged to a species of shark. However, the work of University of Portsmouth Ph.D. student Roy Smith revealed that, in fact, they belonged to a new species of pterosaur.

Sharkosaur

Smith was examining (what we believed to be) the shark fin spines found in the fens when he noticed that they weren’t spines at all. They definitely looked the part, at least superficially, but there were also some details that didn’t fit the bill. Unfortunately, they were just teeth (connected to a bit of beak), so we don’t have enough material to describe the species it belonged to.

“One such feature are tiny little holes where nerves come to the surface and are used for sensitive feeding by the pterosaurs. Shark fin spines do not have these, but the early paleontologists clearly missed these features,” he explains. “Two of the specimens discovered can be identified as a pterosaur called Ornithostoma, but one additional specimen is clearly distinct and represents a new species. It is a palaeontological mystery.”

“Unfortunately, this specimen is too fragmentary to be the basis for naming the new species. Sadly, it is doubtful if any more remains of this pterosaur will be discovered, as there are no longer any exposures of the rock from which the fossils came. But I’m hopeful that other museum collections may contain more examples, and as soon as the Covid restrictions are lifted I will continue my search.”

Smith’s supervisor, Professor Dave Martill, explains that the material we do have “simply differs from Ornithostoma [a pterodactyl lineage] in subtle ways”, similarly to how “a great white egret might differ from a heron”. He adds that it’s unlikely that the animal had a significantly different body structure to other pterodactyls, but that it likely diverged most in areas such as “color, call, and behavior than in the skeleton”. Still, he describes the findings as “tantalizing”.

“Pterosaurs with these types of beaks are better known at the time period from North Africa, so it would be reasonable to assume a likeness to the North African Alanqa”, he adds. “This is extremely exciting to have discovered this mystery pterosaur right here in the UK.”

Part of the significance of the work is finding hints of a new species, the two researchers say. But they’re also valuable in showcasing how re-examining dusty museum collections for old material we assume was already identified can help us make whole new discoveries.

The paper “Edentulous pterosaurs from the Cambridge Greensand (Cretaceous) of eastern England with a review of Ornithostoma Seeley, 1871” has been published in the Proceedings of the Geologists’ Association.

Shark skin protects wounds from infection

Could this blacktip reef shark provide the answer to curing bacterial infections? IMAGE: Wikipedia

Sharks have long shown to exhibit a remarkable resilience to skin infections around wounds. So much so, that a group from King Abdullah University of Science and Technology’s (KAUST) Red Sea Research Center wanted to find out why.

To do this, the international team collected skin mucus samples from the backs and gills of wild-caught blacktip reef sharks around the Seychelles Islands. Next, they sequenced the 16S rRNA gene from these samples in order to identify the bacteria.

What the researchers found was….well, nothing. The scientists’ analysis revealed no difference between the bacterial communities on injured skin on gills and uninjured gills or backs. Basically, there was no evidence of infection around the wounds. “We were surprised not to find any substantial change in the skin bacterial communities,” says Claudia Pogoreutz, the postdoctoral fellow who led the study.

Pogoreutz’s team was able to locate differences in the bacterial communities gathered from the skin of sharks at different locations. While the sites were only just a few kilometers apart, they could be relatively isolated from each other by factors like ocean currents and the reluctance of the blacktip reef sharks to migrate between habitats or cross deeper straits. The differences in shark skin microbial communities may reflect differences in the ambient environment, such as temperature, population density, nutrient availability or pollution, but scientists cannot rule out the possibility that the changes could provide an adaptive benefit to the sharks.

“This suggests shark skin doesn’t become infected easily and that the native bacterial community of the skin can be maintained even after injury,” says Pogoreutz. “We really need to delve deeper into bacterial functions and innate immunity of sharks to understand what is really going on and how wound healing in sharks is mediated.”

Based on their findings, the researchers identified a core skin microbiome that is conserved across blacktip reef sharks, alongside site-specific differences. The team also found no changes in the microbiome around wounds, suggesting that they don’t get infected or that any infections are too mild to detect.

The idea of a shark’s ability to stave off infection comes at a time when, according to the U.S. Centers for Disease Control and Prevention, bacteria cause more than 2 million infections and 23,000 deaths in the U.S. every year. As a result of overusing antibiotics, bacterial resistance to these drugs is on the rise, which makes it much more interesting how sharks are able to avoid these infections and how these findings might be used to benefit humans.

Already, scientists are using sharks to test the waters for new technology to fight the spread and growth of microbes. For example, Sharklet AF is a coating designed to mimic a shark’s skin, and it reduces the ability of bacteria to adhere to surfaces. But long-term use would result in bacteria accumulation. Researchers added titanium dioxide (TiO2) nanoparticles, which are antibacterial, to a shark skin material that would efficiently fight off microbes.

The shark skin surface without nanoparticles reduced the attachment of E. coli by 70 percent compared to smooth films. But shark skin surfaces with TiO2 nanoparticles exposed to UV light for one hour killed off over 95 percent of E. coli and 80 percent of Staphylococcus aureus. So, attempts are being made to replicate nature’s own bacterial defenses.

However, some questions about the KAUST study do remain. Are regional differences playing a role? Is the microbiome contributing to wound healing and infection resistance? “There’s still so much to learn with respect to shark skin-associated bacteria,” says Pogoreutz.

The American Pocket Shark was first discovered in the Gulf of Mexico in 2010. Credit: Mark Doosey.

Scientists describe new pocket shark species that glows in the dark

There are only two known species of pocket sharks: one of them lives deep in the Gulf of Mexico and glows in the dark. This species was just formally described by researchers at Tulane University.

The American Pocket Shark was first discovered in the Gulf of Mexico in 2010. Credit: Mark Doosey.

The American Pocket Shark was first discovered in the Gulf of Mexico in 2010. Credit: Mark Doosey.

Sharks have a really bad (and unwarranted) reputation. Millions of people can’t enjoy the ocean as much as they would like to because of their fear of sharks — a fear instilled by the 1975 release of the movie Jaws and perpetuated by subsequent films like Open Water and The Shallows ever since. However, the truth is shark-related incidences are very rare. According to the International Shark Attack File, in 2016 there were 81 unprovoked attacks worldwide, of which only four were fatal. And although to most people the word “shark” conjures up mental images of menacing great whites, there are more than 500 different shark species, the vast majority of which are completely harmless.

One such harmless species is the American pocket shark (Mollisquama mississippiensis) a pocket shark that was discovered in the central Gulf of Mexico in February 2010 but which was formally classified just recently. This tiny shark measures only 14 centimeters (5.5 inches) in length and has two defining features.

For starters, it features pockets tucked in behind its pectoral fins (hence its name), and secondly, it also sports glands that produce a bioluminescent fluid. It is only the 3rd known shark species that may squirt luminous, glow-in-the-dark liquid.

Credit: Jesse Wicker NOAA/NMFS Miami Laboratory.

“In the history of fisheries science, only two pocket sharks have ever been captured or reported,” said Mark Grace, a biologist at the National Oceanic and Atmospheric Administration (NOAA).

“Both are separate species, each from separate oceans. Both are exceedingly rare.”

Compared to the other pocket shark originally found in the Pacific Ocean, the American pocket shark not only has light-producing photophores covering much of its body but also fewer vertebrae. In order to identify and classify the new shark species, Tulane researchers used a dissecting microscope, along with X-ray imagery and high-resolution CT scans.

“The fact that only one pocket shark has ever been reported from the Gulf of Mexico, and that it is a new species, underscores how little we know about the Gulf – especially its deeper waters – and how many additional new species from these waters await discovery,” said Henry Bart, director of the Tulane Biodiversity Research Institute.

Megalodon.

Megalodon’s teeth evolved over 12 millions years, researchers find

These “ultimate cutting tools” were a long time in the making.

Megalodon.

Teeth are the only reliably identifiable fossils from Carcharocles megalodon. They’re also damn huge.
Image credits Kristen Grace / Florida Museum of Natural History.

The teeth of megalodon (Carcharocles megalodon), the largest shark ever to prowl the oceans, look like daggers. They’re up to 7 inches (18 cm) long and shaped like blades. But it took them millions of years to evolve into their final shape, new research reveals. The findings created more questions than they answered, as we still don’t know why the process took so long or why it started in the first place.

Big fish, bigger bite

“This transition was a very long, drawn-out process, eventually resulting in the perfect cutting tool — a broad, flat tooth with uniform serrations,” said study lead author Victor Perez, a doctoral student in geology at the Florida Museum of Natural History.

“It’s not yet clear why this process took millions of years and why this feature [serration] was lost.”

Megalodon has to be one of the most awe-inspiring and mysterious animals out there. It was the largest shark ever seen on Earth, but the only trace they’ve left is their teeth. Which is quite fitting for a shark.

But these teeth, according to Perez’s team, evolved over 12 million years. The researchers analyzed the evolutionary path of megalodon teeth and those of its immediate ancestor, Carcharocles chubutensis. Their study revealed a surprisingly slow and gradual process, in which they shifted from large teeth flanked by cusplets to regular, cusplet-less teeth.

The team performed a “census of teeth,” analyzing 359 fossils along with the precise location of their retrieval at the Calvert Cliffs on the western shore of Maryland’s Chesapeake Bay — an area that used to be an ocean in C. chubutensis and megalodon’s day.

Megalodon’s earliest ancestor, Otodus obliquus, boasted three-pronged teeth (i.e. teeth with cusplets) that acted more like forks, the team writes. This suggests that O. obliquus dined on fast-moving (but not too large) fish, and it needed teeth to pin them in place. This species effectively forms the baseline from which later megatooth shark species derived.

The fossil record at Calvert Cliffs spans from about 20 to 7.6 million years ago, so they overlap with both C. chubutensis and megalodon. Perez’s team found a consistent decrease in the number of teeth with lateral cusplets over this timespan. About 87% of teeth from 20 to 17 million years ago had cusplets, falling to about 33% roughly 14.5 million years ago. By 7.6 million years, no fossil teeth had cusplets.

But here’s where the results start getting muddy. While the team notes that adult C. chubutensis had cusplets, and adult megalodon did not, they also caution that this feature is not a reliable identifier of which species a tooth belonged to — juvenile megalodon could have cusplets, making it virtually impossible to discern whether a tooth with cusplets came from C. chubutensis or a young megalodon. Furthermore, some teeth analyzed for the study had tiny bumps or pronounced serrations where cusplets would be. A set of teeth from a single shark even had cusplets on some, no cusplets on others, and replacement teeth with reduced cusplets.

While definitely interesting from a paleontological and biological point of view, such specimens make it virtually impossible for the team to draw clean lines between different species. They can’t pinpoint when megalodon first appeared or when C. chubutensis went extinct.

“As paleontologists, we can’t look at DNA to tell us what is a distinct species. We have to make distinctions based off of physical characteristics,” says Perez. “We feel it’s impossible to make a clean distinction between these two species of sharks. In this study, we just focused on the evolution of this single trait over time.”

So what can the study, then, tell us? Well, it does help to flesh out our understanding of how later megatooth species (such as megalodon) lived, how they hunted, and a bit or two about how they handled disease.

Megalodon fossils have flat teeth, often with serrated edges. Based on their shape, they likely performed a different job than that of its earliest ancestor: that of killing (or at least, mortally wounding) large, fleshy animals like whales or dolphins. Megalodon likely hunted in a single-strike manner: it charged at its prey and chomped down hard. Whatever didn’t die on the spot was left immobilized or too crippled to run away, and bleeding heavily.

“It would just become scavenging after that,” says Perez. “A shark wouldn’t want to grab and hold onto a whale because it’s going to thrash about and possibly injure the shark in the process.”

Lateral cusplets may have been used to grasp prey, according to Perez, which could explain why they disappeared as these sharks shifted to a new hunting style. It’s also possible that the cusplets kept food out from between the sharks’ teeth — so they helped prevent gum diseases. But, frankly speaking, the team simply doesn’t have enough information to know why these structures evolved out of the shark’s teeth.

“It’s still a mystery,” Perez says. “We’re wondering if something was tweaked in the genetic pathway of tooth development.”

One point I found particularly interesting was how important ‘beachcombers’ were for this study. The team says that vast majority of teeth they analyzed were discovered by amateur fossil collectors and donated to museum collections.

“This study is almost entirely built on the contributions of amateur, avocational paleontologists,” Perez notes. “They are a valuable part of research.”

The paper “The transition between Carcharocles chubutensis and Carcharocles megalodon (Otodontidae, Chondrichthyes): lateral cusplet loss through time” has been published in the Journal of Vertebrate Paleontology.

Credit: Wikimedia Commons.

Great white shark genome might teach us how to heal faster or stave off cancer

Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

Great whites are some of the most recognizable marine species. Our fascination for these majestic, but also fearsome creatures deepens now that scientists have completed the first genome sequencing of the iconic apex predator.

Scientists sink their teeth in the great white’s genome

The great white’s genome was decoded by an international team of researchers, including those at the Nova Southeastern University’s (NSU) Save Our Seas Foundation Shark Research Center, Guy Harvey Research Institute (GHRI), Cornell University College of Veterinary Medicine, and Monterey Bay Aquarium.

“Decoding the white shark genome is providing science with a new set of keys to unlock lingering mysteries about these feared and misunderstood predators – why sharks have thrived for some 500 million years, longer than almost any vertebrate on earth” said Dr. Salvador Jorgensen, a Senior Research Scientist at the Monterey Bay Aquarium, who co-authored the study.

According to the results, the great white genome contains one-a-half times more information than the human genome. That was not surprising to learn, given that they have 41 pairs of chromosomes, whereas humans have only 23.

There’s no doubt that great whites (Carcharodon carcharias) have experienced tremendous evolutionary success. They’re found throughout most of the world’s oceans, grow up to half the length of a bus, have more than 300 razor-sharp, triangular teeth arranged in seven rows, can detect a seal from two miles away, and are the top of the food chain. Their only threat is humans, whose overfishing and illegal hunting have caused the great white shark to be listed as a vulnerable species on the IUCN Red List.

Not only can great white grow to a large size, but they also have a long lifespan, easily reaching 70 years in the wild. But, despite their size and lifespan, the predators rarely get cancer. Previously, research had established a linear relationship between an animal’s body size and the incidence of cancer, but the great white seems to be one of those rare exceptions. The new study suggests that this is partly due to the great white’s genome stability — genetic adaptations which help preserve its genome.

Another remarkable feature of great whites is their extraordinary ability to regenerate quickly. Researchers have tracked back this ability to certain genes that are tied to fundamental pathways involved in wound healing, including a key blood clotting gene.

“Not only were there a surprisingly high number of genome stability genes that contained these adaptive changes, but there was also an enrichment of several of these genes, highlighting the importance of this genetic fine-tuning in the white shark,” said Mahmood Shivji, who is the director of NSU’s Save Our Seas Foundation Shark Research Center.

“Genome instability is a very important issue in many serious human diseases; now we find that nature has developed clever strategies to maintain the stability of genomes in these large-bodied, long-lived sharks,” said Shivji. “There’s still tons to be learned from these evolutionary marvels, including information that will potentially be useful to fight cancer and age-related diseases, and improve wound healing treatments in humans, as we uncover how these animals do it.”

Decoding the white shark’s genome is a great breakthrough that will help conserve the species. For instance, the genome data could be used to better assess white population dynamics. The insight gained from the great white’s genome might also lead to novel cancer drugs in the future.

The findings were reported in the journal PNAS. 

Galagadon.

Paleontologists discovered a new species of ancient shark — and it was so, so tiny

Researchers at the North Carolina State University have discovered a new species of ancient shark. While related to the megalodon, the largest shark ever to prowl the oceans, the new species — dubbed Galagadon nordquistae — is quite small.

Galagadon.

An illustration of what Galagadon nordquistae might have looked like.
Image credits Velizar Simeonovski / Field Museum.

The same silt that held the world’s most famous and complete T. rex fossil (specimen  FMNH PR 2081, or, more-pronounceably, “Sue“) yielded a surprising new find: a previously unknown species of freshwater shark. Christened Galagadon nordquistae, the species was remarkably small, growing to approximately 12-18 inches (30.5-45 cm) in length.

One of its most striking features also gave the species its name: this shark’s tiny teeth resemble alien spaceships from the 1980s video game Galaga.

Small shark, tiny teeth

“The more we discover about the Cretaceous period just before the non-bird dinosaurs went extinct, the more fantastic that world becomes,” says study lead author Terry Gates, lecturer at North Carolina State University and research affiliate with the North Carolina Museum of Natural Sciences.

G. nordquistae is related to both the huge (and now-extinct) megalodon and modern-day carpet sharks, such as the “whiskered” wobbegong. It lived during the Cretaceous in what is today South Dakota — likely in rivers and ponds, the team writes. South Dakota was very different 67 million years ago, with sprawling forests, deep swamps, and winding rivers, says Gates.

During its day, G. nordquistae likely didn’t pester the big folk at the top of the food chain — rather, he dealt with those living at the bottom. Quite literally: Galagadon had teeth that were good for catching small fish or crushing snails and crawdads, not for munching on dinosaurs.

Over two dozen of the shark’s tiny, fossilized teeth — each one measuring less than a millimeter across — were recovered from the same sediment in which paleontologists at the Field Museum uncovered Sue. Gates sifted through the material (almost two tons of it) with the help of volunteer Karen Nordquist, whom the species name of nordquistae, honors. Despite their very tiny stature, Gates says the discovery of Galagadon is an important step towards fleshing out our understanding of the fossil record.

“Every species in an ecosystem plays a supporting role, keeping the whole network together,” he says. “There is no way for us to understand what changed in the ecosystem during the mass extinction at the end of the Cretaceous without knowing all the wonderful species that existed before.”

Gates himself says that finding these microscopic teeth “sitting right beside the bones of the largest predators of all time” is nothing short of amazing.

“These teeth are the size of a sand grain. Without a microscope you’d just throw them away.”

Gates credits the idea for Galagadon’s name (based on the video game Galaga) to middle school teacher Nate Bourne. Bourne worked alongside Gates in paleontologist Lindsay Zanno’s lab at the North Carolina Museum of Natural Sciences.

The paper “New sharks and other chondrichthyans from the latest Maastrichtian (Late Cretaceous) of North America” has been published in the Journal of Paleontology.

Otodus megalodon. Credit: Flickr, Elena Regina.

Megalodon may have been warm-blooded — and this may have ultimately doomed the huge predator

Otodus megalodon. Credit: Flickr, Elena Regina.

Otodus megalodon. Credit: Flickr / Elena Regina.

The extinction of the largest fish to have ever swum the world’s oceans is shrouded in mystery. Megalodon dominated the oceans for millions of years during the Miocene and Pliocene epochs until it abruptly disappeared before the onset of a massive ice age 2.6 million years ago. A new study suggests that the iconic extinct shark was significantly warmer than its modern cousins, which may have sped up its demise in the face of cooling waters due to climate change.

An active metabolism that needed a lot of food

In comparison to Megalodon (Otodus megalodon), the Great White Shark seems like a guppy. The extinct shark achieved lengths up to nearly 20 meters and weights exceeding 20,000 kg — and if its formidable size wasn’t enough, the huge fish also had razor sharp teeth, each as long as 18 centimeters (about the size of a human hand).

Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

The earliest Megalodon fossils — almost exclusively comprised of teeth — suggest the marine predator first appeared about 23 million years ago. A 2014 study performed by Swiss researchers found that all signs of the creature’s existence ended 2.6 million years ago. It’s not clear what brought Megalodon’s demise but a new study presented at the annual meeting of the American Geophysical Union (AGU) suggests that thermoregulation may have played a major role.

The team of researchers at William Paterson University (WPU), the University of California Los Angeles, and DePaul University employed a novel geochemical method called clumped isotope thermometry (CIT). By analyzing the concentrations of oxygen-18 (18O) and carbon-13 (13C) isotopes within the carbon dioxide (CO2) of tooth enamel, it’s possible to tease out an animal’s body temperature. A lower concentration of clumped isotopes means that the enamel was formed at a higher body temperature

In order to verify the method, the researchers first worked with teeth from aquarium-reared and wild-caught sharks from areas with known temperature records. The method proved quite accurate.

Next, once the method was calibrated, the researchers analyzed the teeth of Megalodon and other ancient shark species, showing that the huge marine creature was a bit warmer than its coexisting shark species and modern sharks such as great whites.

The ancestors of sharks like makos and great whites lived alongside Megalodon millions of years ago, and likely had a temperature of about 20 to 30 degrees Celsius (68 to 86 degrees Fahrenheit), whereas Megalodon had a body temperature as high as 35 to 40 degrees Celsius (95 to 104 degrees Fahrenheit). That’s about the same body temperatures as whales, which are endothermic (warm-blooded).

Perhaps, Megalodon may have also been warm-blooded, although that is quite an assumption, judging from enamel isotopes alone. The relatively high body temperature, however, may be a sign of an active metabolism that required lots of prey and frequent feeding. When the planet went through a particularly tough ice age, Megalodon may have been too big for its own good, with too little prey to spare in order to sustain its high body temperature. Coupled with competition from other predators, such as toothed whales, Megalodon went on a downward spiral.

“While still preliminary, these results may provide clues as to what may have led to the demise of O. megalodon during the Pliocene. For example, one hypothesis is that O. megalodon consumed large quantities of prey in order to maintain such a high body temperature. However, cooling of ocean temperatures during the Pliocene would have constrained the species to lower latitudes where ocean temperatures were warmer, whilst its preferred prey (e.g., whales) evolved traits to adapt to cooler temperatures of the higher latitudes. Therefore, large climatic shifts combined with evolutionary limitations may provide the “smoking gun” for the extinction of the largest shark species to ever roam the planet,” wrote the researchers.

Next, the authors plan to analyze other isotope ratios in megalodon teeth, such as calcium-44/calcium-40 or oxygen-16/oxygen-18. The former can reveal more details about a creature’s diet, such as if a certain prey was more abundant, whereas the latter ratio can record information like seawater chemistry and temperature. Together, all of these methods could help paint a bigger picture of Megalodon’s demise.

The bonnethead shark. Credit: Wikimedia Commons.

Scientists find the first plant-eating shark — but it still likes to hunt

Jaws would’ve been a heck of a lot less terrifying had it stared the bonnethead shark. According to a recent study, this shark enjoys a diet of bony fish, crabs, snails, and shrimp — but also seagrass. This makes it the first omnivorous shark that we know of.

The bonnethead shark. Credit: Wikimedia Commons.

The bonnethead shark. Credit: Wikimedia Commons.

For some time, biologists have been observing that bonnetheads (Sphyrna tiburo) ingest seagrass in addition to their favorite crustaceans and shellfish. However, because their stomach is almost identical to other meat-eating sharks, being highly specialized for a diet revolving around protein, scientists had always assumed the seagrass was consumed by accident.

But it seems like the bonnetheads really like seagrass, which they ingest for its nutritional value. This was proven by Samantha Leigh at the University of California Irvine and her colleagues, who ran a series of tests to determine how much of this seagrass diet could be digested. What an animal consumes is not necessarily the same as what it digests and retains nutrients from.

First, the researchers planted seagrass from Florida Bay in their lab. To track the plants along the food chain that would eventually reach the sharks, researchers added a specific carbon isotope to the water.

Five bonnetheads were served a diet made up of 90% seagrass and 10% squid in a controlled environment in the lab. Three weeks later, all the sharks had put on weight, suggesting that the animals must have derived calories from the plant-based diet.

To be sure, researchers ran a new series of tests, meant to measure how much of the plant matter was digested and how much of it simply passed through.

bonnethead-diet

Credit: Leigh et al.

Blood tests found high levels of the carbon isotope in both the sharks’ bloodstream and liver, suggesting that the seagrass nutrients were being absorbed.

Finally, Leigh and colleagues found the types of digestive enzymes that break down the plant-based food. Carnivores like white sharks usually have very low levels of enzymes that break down fibers and carbs. The bonnethead sharks, however, had copious levels of these types of enzymes. Over half of the organic matter found in seagrass was digested by the bonnetheads.

“Bonnethead sharks are not only consuming copious amount of seagrass but they are actually capable of digesting and assimilating seagrass nutrients, making them clear omnivores,” the researchers wrote in their study.

“This is the first species of shark ever to be shown to have an omnivorous digestive strategy.”

Approximately 4.9 million individuals swim in the coastal waters of the USA in the Atlantic and Gulf of Mexico. Their great numbers will force researchers to re-evaluate the role that bonnetheads play in seagrass meadows, which are critical ecosystems that provide habitat for thousands of fish species, filter the surrounding water, act as a sink for atmospheric CO2, and produce large quantities of oxygen.

“Considering bonnethead sharks as omnivores, rather than carnivores, in models of seagrass meadow function, and then testing the predictions of those models for management purposes, changes our understanding of the fluxes of nutrients and energy among trophic levels within each part of these ecosystems,” the authors wrote in the Proceedings of the Royal Society B.

The researchers aren’t sure when the bonnetheads started eating plants in their evolutionary history but it’s possible other shark species do it as well.

Mako shark (Isurus oxyrinchus). Credit: Wikimedia Commons.

Fastest shark on Earth might inspire the next-generation of drones and wind turbines

Sharks are some of nature’s most able swimmers. Now, American researchers have revealed one of the secrets that enable the shortfin mako to swim faster than any other shark on Earth. It’s all in the scales, according to a study published in the Journal of the Royal Society Interface.

Mako shark (Isurus oxyrinchus). Credit: Wikimedia Commons.

Mako shark (Isurus oxyrinchus). Credit: Wikimedia Commons.

Shortfin mako sharks (Isurus oxyrinchus) are not only beautiful, but they’re also believed to be the fastest-swimming sharks in the ocean. They zip through the water at lightning speed, and in short bursts can swim up to 44 miles per hour. Moreover, these sharks are famous for making spectacular leaps of up to six meters out of the water.

This extraordinary prowess can be explained by the shark’s high tail which it uses to produce maximum thrust, propelling it forward in extreme bursts of speed. Its streamlined body is also built for optimum speed underwater, featuring a distinct crescent-shaped caudal fin and a long, conical snout.

But that’s not all, as Harvard University and University of South Carolina researchers recently found out. The team used micro-CT scanning to image even the tiniest features on the shark’s surface. This allowed them to model the denticles (scales) of the shark in three dimensions.

“The skin of sharks is covered by thousands and thousands of small scales, or denticles, which vary in shape and size around the body,” said George Lauder, a Professor at Harvard and co-author of the research.  “We know a lot about the structure of these denticles — which are very similar to human teeth — but the function has been debated.”

The tooth-like scales of the mako shark were previously thought to have drag-reducing properties. However, this new study suggests that, in fact, they’re more suited for creating lift.

Environmental scanning electron microscope image of denticles from the shortfin mako shark (a) and of the parametric 3D model (b). These denticles were arranged in a wide range of different configurations on an aerofoil, two examples of which are shown here (c,d ). Credit: Harvard University.

Environmental scanning electron microscope image of denticles from the shortfin mako shark (a) and of the parametric 3D model (b). These denticles were arranged in a wide range of different configurations on an aerofoil, two examples of which are shown here (c,d ). Credit: Harvard University.

To measure the lift effect, the team 3-D printed the denticles with trident-like ridges on the surface of an airfoil — a curved aerodynamic cross-section. Overall, over 20 different configurations of denticle size and row positions were tested on airfoils inside a water flow tank. The experiments revealed that the 3-D printed denticle-shaped structures enhanced lift, acting like vortex generators.

Vortex generators are common in most cars and aircraft, but these typically have a blade-like design. The mako shark-inspired design, however, proved to be far superior.

“These shark-inspired vortex generators achieve lift-to-drag ratio improvements of up to 323 percent compared to an airfoil without vortex generators,” said August Domel, a Ph.D. student at Harvard and co-first author of the paper. “With these proof of concept designs, we’ve demonstrated that these bioinspired vortex generators have the potential to outperform traditional designs.”

The researchers imagine seeing the design implemented in the next-generation of wind turbines and aircraft. From shark scales to high-power vortex generators — now that’s something!

Scientists track and study sharks by analyzing environmental water DNA

Marine ecologists have developed an innovative way to monitor shark populations. The method could complement or replace current methods, which are expensive and invasive.

Image credits: Bakker et al, 2017 / Salford University / Nature.

It hasn’t been a good decade for sharks around the globe. It is estimated that 100 million sharks are killed by people every year, due to commercial and recreational fishing. Shark finning has grown to alarming proportions, killing anywhere between 63 and 273 million sharks per year. With this, it’s more important than ever to study and understand them, but this is no easy feat.

Almost half of all known shark species are classified as ‘data deficient’, particularly because of how hard it is to study them in their natural habitat. Bating, hooking and filming sharks is costly, time-consuming, and stressful for the animals. So researchers from the University of Salford in the UK have developed a new forensic-like technique.

“Water contains minute fragments of the skin, excretions, blood of animals that have swum through there,” explains Stefano Mariani, professor of conservation genetics at the University of Salford. “It’s just like when detectives do a forensic search of a crime scene, and can locate tissues and cells that contain the DNA of the suspects”

The team of researchers took samples from four sites in the Caribbean and three in the Pacific Coral Sea. They used a process called metabarcoding — a rapid method of biodiversity assessment that combines two technologies: DNA-based identification and high-throughput DNA sequencing. Metabarcode datasets are comprehensive and relatively easy and fast to obtain, both on land and on water. The team reported finding more shark DNA sequences in less anthropogenically impacted areas. For instance, the more isolated and the protected areas had larger amounts of shark DNA.

“The beauty of our method is that we can get a picture of shark diversity without the need for chasing, baiting and hooking them – so it is a lot faster for conservation scientists and less traumatic for the animals,” added Judith Bakker, the lead author of the study.

Image credits: Bakker et al, 2017 / Salford University / Nature.

This method could be applied pretty much anywhere with ease, making any pocket of water a potential gold mine of data, researchers say. As such, the findings could have a massive impact on conservation measures.

“In order to protect these elusive animals and their ecosystems, we must be able to rapidly assess many areas at repeated time intervals,” Mariani continues. “eDNA should prove a big step forward because basically anyone can collect water samples, and every bottle of water is a potential gold mine of data.”

Of course, much work is still needed to be done in order to be able to clearly identify different species of sharks, as well as understanding the impact of oceanic currents and depth on the transport of trace DNA, but results are certainly encouraging.

The study was published in Science Reports.

These sharks thrive in a real-life underwater volcano

It’s not Sharknado, but it’s definitely Sharkcano — researchers have found thriving, active sharks in an underwater volcano in the Solomon Islands near Papua New Guinea.

Life always finds a way; whether we’re talking about tardigrades living in extreme environments, plants in frozen landscapes, or, as it turns out, sharks in a volcano. In January 2014, National Geographic reported the unexpected discovery of several marine species living inside an active underwater volcano caldera, in the Kavachi Volcano in the Southwest Pacific Ocean (around the Solomon Islands). Particularly surprising was the presence of sleeper sharks.

“We were freaking out,” said University of Rhode Island Ph.D student Brennan Phillips to National Geographic.

Thought to be both predators and scavengers, sleeper sharks feed by suction and cutting of their prey. They live in frigid depths, where light is scarce and food is even scarcer. So what on Earth were these creatures doing in the hot, acidic caldera? That’s a good question, which researchers wanted to answer. So scientists went back for another expedition. But how do you explore an environment that’s toxic and hot enough to injure or even kill you? Why, you send in the robots, of course.

“Our goal is to send instrumentation there to get meaningful data, but sometimes it’s really fun to just blow stuff up,” says National Geographic explorer and ocean engineer Brennan Phillips.

Image credits: National Geographic / Youtube.

Phillips reunited with his 2015 expedition mates — Alistair Grinham of University of Queensland and Matthew Dunbabin of Queensland University of Technology and Director of GFB Robotics — to measure pH, carbon dioxide, temperature fluctuations, acidity, and have a glimpse of the location.
“The smaller robots have acoustic depth sounders for gathering bathymetry of the vent region, surface water temperature sensors, accelerometers, and cameras. The larger robots carry greenhouse gas monitoring sensors and measure direct gas release to the atmosphere as well as physical air samples. We also have simple drifting robots that are capable of collecting water samples,” says Dunbabin.

The water inside the caldera is hot, acidic, and turbid. Image credits: National Geographic / Youtube.

They’ve learned that Kavachi is a strong greenhouse gas emitter, water temperatures are ten degrees higher than normal, and the pH drops sharply. The water is also very cloudy. None of these things are really surprising, and they’re all these bad for fish, and but are they equally bad for sharks?
For now, that’s still an open question. While the expedition helped shed more light on the Kavachi situation, we still don’t know how the sharks got there, why they’re enjoying the place so much, and how they will adapt in the future. Can they anticipate an impending eruption? What do they feed on? Those are all still questions that need to be answered. These learnings are now driving the development of new experiments for the next trip, Dunbabin says, and the exploration of Kavachi is far from over. In fact, it may just be beginning.
Shark fin.

Most shark fins and ray gills sold in Vancouver come from threatened, trade-banned species

DNA sequencing of over 100 shark fins and manta ray gills in Vancouver has revealed that over half come from threatened species who are banned for trade under international law.

Shark fin.

Image via Pixabay.

As far as traditional Chinese delicacies go, shark fins are more on the expensive side. They’re used to make soups that can sell for over US$100 per bowl and are generally served during special occasions. Manta ray gill rakers, tiny filaments which these species use to filter nutrients out of water are used in traditional Chinese medicine, advertised as effective against all sorts of conditions from smallpox to cancer according to the conservation group Manta Ray of Hope.

The problem with them is two-fold. First, about a quarter of shark and ray species around the world are threatened due to overfishing, according to the International Union for the Conservation of Nature (IUCN). Secondly, they’re sourced very inhumanely — shark fins, for example, are cut off from live animals which are then thrown back into the ocean where they die a slow, agonizing death. So the commercial use of these commodities sourced from several species of both shark and ray are banned for international trade in an effort to give the animals respite from commercial fishing, and allow them an opportunity to recover.

But that doesn’t mean people don’t still buy and sell them, according to a research team led by Dirk Steinke from the University of Guelph. They’ve tested over 100 samples of the items available for purchase in Vancouver, Canada, and report that over 71% belong to species that are considered endangered.

Fin-ding soup

Yokohama shark fin.

Dried shark fins on display in a traditional Chinese medicine shop in Yohokama.
Image credits Chris 73 / Wikimedia.

According to Steinke, Canada is the largest importer of shark fins outside of Asia. The Senate of Canada’s website reports that in 2015, the country imported some 114,540 kilograms (252,517 pounds) of fins, and the CBC cites Statistics Canada as saying this increased to 140,750 kilograms (310,300 pounds) of shark fins worth $3.08 million (of the total $11,3 million estimated global trade) in 2016.

Steinke’s research was in part prompted by the Vancouver Animal Defence League, which was concerned that fins from protected species were being sold locally. Because these fins are very expensive, the team used 71 dried fin samples collected in 2011 and 2012 by volunteers and University of Guelph researchers, and 54 ray gill plates obtained by scientists working with the Save Our Seas Shark Research Centre at the Nova Southeastern University from Hong Kong and mainland China.

“It took them awhile to get the money together because they’re not cheap,” Steinke said.

The samples were analyzed using DNA barcoding, a technique developed at the University of Guelph which allows for species to be pinpointed using relatively short bits of DNA. The drying process actually helped speed this along, Steinke said, as it helps preserve DNA in a usable form.

Overall, the team traced the samples back to 20 species of sharks and some 5 species of rays. Roughly 56% of them are on the IUCN Red List as endangered or vulnerable, and some 24% are close to threatened status. Seven of the shark species and all five ray species are also banned from international trade under the Convention on International Trade in Endangered Species treaty. It must be pointed out that the ban for most of these species went into effect between 2014 and 2017, which is after the samples were collected. However, the team did trace some samples back to species which did have protected status and was banned from trade at the time the samples were collected, such as the whale shark.

Banned but not gone

Chinese shark fin soup.

Chinese shark fin soup in Austin, Texas.
Image credits harmon / Wikimedia.

That last tidbit, coupled with the fact that there are “confirmed occurrence of these species’ body parts in recent trade suggests ongoing market demands,” the researchers wrote. Although almost three-quarters of shark and ray species are not considered threatened, are not banned from trade in Canada, and are not at risk of extinction, it’s “very frustrating, although not unexpected” that we see such a large percentage of banned species still up for trade — rarer types of fins will, after all, demand a higher market price, offering an incentive in their continued trade.

Compounding the problem is that authorities simply lack the means to meaningfully impose the ban. It’s virtually impossible to tell what species a dried fin belongs to simply by looking at it. Retailers can reliably expect to get off without being caught and fined, and along with the high price fetched by the fins selling illegal species “might still pay off,” Steinke says. DNA testing can reliably trace the source species, and is quite cheap at US$10 a pop — but it can take up to several weeks for a result.

Steinke hopes that raising awareness and lowering demand will wither the market and at least help some sharks make it out alive — and eventually stop it altogether. He also hopes the results (and ideally, public support for such measures) will goad politicians into banning shark fin sales on a larger scale. Similar bans are already in effect at a local level in over a dozen municipalities in Canada, but bills for a federal ban have already failed to pass in 2013 and 2016.

These animals have been around for longer than trees, and we’re killing them over what’s widely agreed to be a pretty tasteless soup. Traditions do have a very important role to play in human life, granted. But there’s a point where we have to take the reigns, a point beyond which getting bogged down in the past will make tomorrow less — and in this case, we’re literally eating the viability of tomorrow’s oceans. Although, that seems to be a very human-like take on a lot of very serious issues.

Third time’s the charm as far as bans go, hopefully.

The paper “DNA analysis of traded shark fins and mobulid gill plates reveals a high proportion of species of conservation concern” has been published in the journal Scientific Reports.

Scientists find deep-sea miniature shark that glows in the dark

The shark inhabits the depths of the Pacific and sports an exceptionally large nose.

Etmopterus lailae is a member of the Lanternshark family, living more than 300 meters (1000 feet beneath the surface). Image credits: Stephen Kajiura, Florida Atlantic University.

A light in the darkness

If you go deep enough, underwater life starts to become really bizarre. Where light just barely goes through (or doesn’t at all), pressure starts to mount up, and temperatures drop significantly, creatures have adapted in complex and often strange ways. Eyes can grow very large to capture what little light comes through, or decay completely and abandon any hope of visibility. Membranes and proteins start to develop specific structures to cope with the pressure, and because food is so scarce in the absence of all photosynthesis, fascinating feeding mechanisms have emerged. Among these adaptations, bioluminescence plays a special role.

Bioluminescence is any production and emission of light by a living organism. In the deep oceans, every bit of light can make a difference, and bioluminescence can help in a number of ways. It can serve as a headlight (the so-called photophores of lantern fish), to lure unsuspecting prey (for the anglerfish), or even to attract sexual partners. The oceans are vast and very dark, so that can be a daunting task. Some creatures such as sea cucumbers even use bioluminescence as a “burglar alarm” — whenever they’re attacked by a predator, they light up to attract an even bigger predator to take care of the threat.They can even spray glow-in-the-dark mucus on the predator so that the “police” can find it later.

This newly discovered shark, Etmopterus lailae, is also bioluminescent, but that’s hardly the most remarkable thing about it.

A nose for sharks

Image credits: Stephen M. Kajiura, Florida Atlantic University.

Weighing less than 1 kg (two pounds) and measuring less than 30 centimeters (1 foot), the shark is still a sight to behold. Found in the Pacific Ocean off the coast of Hawaii’s northwestern islands, it looks more like a fairy tale monster than a shark, but that’s to be expected for such a deep dwelling predator.

The shark was discovered 17 years ago, but it took a really long time to properly identify it. At first, Stephen M. Kajiura, the study author thought it wasn’t a new species. When he submitted the findings to a journal, a reviewer told them the shark is not what they think it is. This came as quite a shock — a thrilling one, as Kajiura himself notes.

“There are only about 450 known species of sharks worldwide and you don’t come across a new species all that often. A large part of biodiversity is still unknown, so for us to stumble upon a tiny, new species of shark in a gigantic ocean is really thrilling,” Kajiura said in a university press release.

Working with David A. Ebert, the program director of the Pacific Shark Research Center at Moss Landing Marine Laboratories in California, he was able to identify the shark after all these years. Etmopterus lailae is a member of the Lanternshark family, but it has some striking distinctive features.
“The unique features and characteristics of this new species really sets it apart from the other Lanternsharks,” said Kajiura. “For one thing, it has a strange head shape and an unusually large and bulgy snout where its nostrils and olfactory organs are located. These creatures are living in a deep sea environment with almost no light so they need to have a big sniffer to find food.”

Analyzing and characterizing the shark required diligent categorization and thorough comparisons with other museum specimens. The species also features unusual flank markings that go forward and backward on their bellies, as well as fewer teeth than other sharks.

It’s not clear why this shark is bioluminescent, though the team has some ideas. Most likely, this is how the shark lures in shrimp or other prey and recognizes its mates — as in, to be sure it’s mating with the right species.

This is just the tip of the iceberg, and there’s certainly much more to discover about this species and others like it, but that’s hard to do for obvious reasons. Since 60% of the planet is covered by water more than a mile deep, that makes the deep sea the largest habitat on Earth. It’s also the most unexplored. No doubt, many surprises still await to be discovered. This particular shark, unfortunately for him, is now hosted at the Bernice P. Bishop Museum in Hawaii.
Journal Reference: David A. Ebert, Yannis P. Papastamatious, Stephen M. Kajiura, Bradley M. Wetherbee — Etmopterus lailae sp. nov., a new lanternshark (Squaliformes: Etmopteridae) from the Northwestern Hawaiian Islands. DOI: http://dx.doi.org/10.11646/zootaxa.4237.2.10
Bamboo Shark.

Bamboo sharks really have to put their back into eating — literally

Lacking a tongue, bamboo sharks (Chiloscyllium plagiosum) swallow with their shoulder bones. Other tongue-less sharks and fish species likely use a similar method of swallowing.

Bamboo Shark.

Image credits Steve Childs.

The finding comes from the lab of Ariel Camp, a postdoctoral researcher at Brown University’s Department of Ecology and Evolutionary Biology. Using state of the art X-ray imaging technology, Camp and her team filmed the internal going-ons of bamboo sharks having lunch. These tongueless critters, it seems, rely on their shoulder-blades to create suction when it’s time to swallow.

“They have this long pharynx, and they have to keep food moving down it,” Camp explains.

“We think this is part of a ‘hydrodynamic tongue.’ Sharks and fishes that don’t have a tongue control the motion of fluid within their mouths to manipulate food.”

Put your back into it!

Bamboo sharks’ “shoulder girdle” is made up of a U-shaped assortment of cartilage and muscles which they both for swallowing and control of their front fins, the paper explains. They’re one among several oceanic species that use a suction system to feed. It comes in handy when prying uncooperative pray, for example fish hidden in rocky crevices or dug into the ocean floor. By placing their mouth over the hiding spots, then rapidly opening it — sometimes with help from muscles deeper into their bodies — they create the suction needed to reel a meal in.

While the bamboo sharks’ suction system was documented in literature, whether or not their shoulder girdles played apart was a matter of some debate. The structure serves to support the sharks‘ frontal fins, which they use in a sort-of walking motion to position themselves over prey. As it’s not directly connected to the jaws or any other part of the head, however, it was assumed to remain still and play no part in the feeding process.

But through a method known as X-ray Reconstruction of Moving Morphology (XROMM), which combines skeletal CT scans with high-speed, high-fidelity X-ray “movies” observing tiny implanted markers, Camp’s team was able to create very detailed visualizations of how the sharks’ bones and muscles move while feeding. They fed three sharks pieces of squid and herring, then used XROMM imaging to get a better understanding of how they swallow.

They observed a surprising swing of the shoulder girdle in all three sharks: after closing their mouths, the cartilage quickly rotated backwards from the head by about 11 degrees. While the study only used bamboo sharks, Camp says other suction-feeding sharks probably swing their shoulders in a similar fashion.

Understanding how the sharks’ girdle functions could help explain why and how it evolved in the first place, for them and other species as well. Ultimately, as the structure enables such animals to “walk” around on the seabed, the research could uncover part of the story of how animals eventually made it from the ocean to dry land.

“The girdle shows up [in the fossil record], around the time that jaws evolved,” Camp said.

“We aren’t sure exactly what structures it evolved from or how that happened. Part of understanding that history is understanding what were the functions this structure had to carry out.”

 

The paper “Dual function of the pectoral girdle for feeding and locomotion in white-spotted bamboo sharks” has been published in the journal Proceedings of the Royal Society B.

Megalolamna paradoxodon had grasping-type front teeth and cutting-type rear teeth likely used to seize and slice medium-sized fish and it lived in the same ancient oceans megatoothed sharks inhabited. (Image by Kenshu Shimada)

New ancient car-sized species identified by paleontologists. It was related to Megalodon

Megalolamna paradoxodon had grasping-type front teeth and cutting-type rear teeth likely used to seize and slice medium-sized fish and it lived in the same ancient oceans megatoothed sharks inhabited. (Image by Kenshu Shimada)

Megalolamna paradoxodon had grasping-type front teeth and cutting-type rear teeth likely used to seize and slice medium-sized fish and it lived in the same ancient oceans megatoothed sharks inhabited. (Image by Kenshu Shimada)

Some 20 million years ago, both the Atlantic and the Pacific were haunted by a huge shark the size of a car. The new species, called Megalolamna paradoxodon, was just discovered and researchers think it was related to the biggest shark that ever lived, Megalodon.

It’s very difficult to find shark fossils and it’s not that surprising if you know they’re made of cartilage, not bones. Paleontologists sometimes can find fossils of those parts of the shark made of denser cartilage like the centers of the vertebra, jaw cartilage, and the rostral node in a shark’s snout. However, maybe 99% of all known shark fossils are the teeth. In the case of  Megalolamna p., five tooth samples collected from California, North Carolina, Japan, and Peru were all that scientists had at their disposal.

Shark teeth, however, are enough to learn an awful lot. Each sharks species’ teeth have a unique shape — in the case of Megalolamna p., these are shaped in a mosaic-like pattern. It helped that both front and rear teeth were found, the former used for grasping while the latter for slicing.

The geographical distribution of the new ancient shark's teeth. Credit: Kenshu Shimad

The geographical distribution of the new ancient shark’s teeth. Credit: Kenshu Shimad

Megalolamna p. lived in the Miocene period, about 20 million years ago, and likely ate medium-sized fish. That’s judging from its estimated size, about 12 feet long. The researchers from DePaul University in Chicago who were responsible for the find compared the teeth to those belonging to other extinct and currently living species to come with this estimate.

“The fact that such a large …shark with such a wide geographic distribution had evaded recognition until now indicates just how little we still know about the Earth’s ancient marine ecosystem,” said Kenshu Shimada, the lead author of the study and a paleobiologist at DePaul University in Chicago.

Its size makes the ancient the shark actually smaller than the great white shark, which can grow between 15 and 20 feet in length. However, at this point, it’s very difficult to judge just how big Megalolamna p. could grow. A shark might have smaller or bigger teeth in its jaw which might not reflect the true size of the fish. More fossilized teeth might help settle it.

Megalolamna p.’s cousin, the beast of the ancient high seas called Megalodon, could grow to 60 feet in length and its bite was more powerful than T-Rex’s. Megalodon seemed to have disappeared about 65 million years ago, so that makes the two species 45 million years apart. We know little to nothing about what happened in between this time frame, how Megalodon evolved, what it turned into etc. There are a lot of unanswered questions which only more fossil findings might help settle.

Findings appeared in the journal Historical Biology.