New study challenges consensus scientific belief that sharks are ‘living fossils’

Raw Story | Apr 16, 2014 | Agence France-Presse

Modern sharks are not “living fossil” replicas of their prehistoric ancestors but have evolved significantly over millions of years to develop their hallmark design, a consensus-busting study said Wednesday.

The newly discovered fossil skull of a shark-like ancestor of all jawed vertebrates adds to evidence that a bony skeleton, not a cartilaginous one, was the prototype.

The ancestor, which lived in the Palaeozoic era some 325 million years ago, turns out to have had characteristics of fish with cartilaginous skeletons, like sharks, and of bony ones like salmon and tuna, a reasearch team wrote in the journal Nature.

Scientists have long assumed that modern animals with bony skeletons evolved from a shark-like creature with a frame made of cartilage, thus acquiring bone over time.

Modern-day sharks and rays were thought to most closely represent the original jawed ancestor, having stayed basically unchanged.

But the latest study adds to a new school of thought that sharks shed their bony frames and replaced them with cartilage to become specialised, deep-sea hunters.

“Scientists, and the public, have long thought that today’s sharks are ‘living fossils’ — a group of animals that appeared a long time ago and hardly changed,” study lead author Alan Pradel of the American Museum of Natural History, told AFP.

“Scientists based this on the fact that their skeletons are cartilaginous like those of jawless fish (a sister group comprised of lampreys and hagfish), which are assumed to be more primitive.

“Thus, scientists assumed that modern-day sharks represent the ancestral version of the skeleton of jawed vertebrates.”

But the new fossil challenges this view.

Its skull is arranged very differently to those of sharks, much more like those of bony fishes, Pradel’s team found.

“The common ancestor of jawed vertebrates more closely resembled today’s bony fish than cartilaginous ones,” said Pradel of the study findings.

“That turns the traditional scientific thinking on its head. Today’s sharks are not living fossils, and they are very different to their ancestors.”

The finding means that scientists can probably learn more from bony fishes like salmon and tuna about the early evolution of jawed vertebrates than from sharks, as was long believed.

[Image via Agence France-Presse]

25% of sharks and rays at high risk of extinction

A new assessment by the International Union
for Conservation of Nature (IUCN) has revealed
that a quarter of the world's sharks
and rays are at risk of extinction.

25% of sharks and rays at high risk of extinction
Jan 22, 2014 | Times of India

A new assessment by the International Union for Conservation of Nature (IUCN) has revealed that a quarter of the world's sharks and rays are at risk of extinction.

The latest update to the IUCN's "Red List" of threatened species, which found ray species to be at higher risk than sharks, is part of a first-ever global analysis of these marine species.

Researchers assessed the conservation status of 1,041 shark, ray and chimaera species, which are all so-called "cartilaginous fish," meaning they have skeletons made of cartilage rather than bone. A chimaera is type of jawed fish closely related to sharks and rays.

The researchers found that sharks, rays and chimaeras face a substantially higher risk of extinction than do most other animals.

In fact, only 23 percent of shark, ray and chimaera species are categorized as being safe, or of "least concern," IUCN officials said.

Nick Dulvy, co-chair of the IUCN Shark Specialist Group and Canada Research Chair at Simon Fraser University in British Columbia, Canada, said in a statement that the analysis shows that sharks and their relatives are facing an alarmingly elevated risk of extinction, LiveScience reported.

He said that in greatest peril are the largest species of rays and sharks, especially those living in shallow water that is accessible to fisheries, where they can become entangled in fishing gear a phenomenon known as bycatch.

Source: Asian News International

Radioactive water overruns Fukushima barrier - TEPCO

An aerial view shows workers wearing protective suits
and masks work at a construction site (C) of the shore barrier
to stop radioactive water from leaking into the sea at Fukushima
Daiichi nuclear power plant on August 9, 2013. (Reuters/Kyodo)

Radioactive water overruns Fukushima barrier - TEPCO
Aug 8, 2013 | RT

Contaminated groundwater accumulating under the crippled Fukushima nuclear power plant has risen 60cm above the protective barrier, and is now freely leaking into the Pacific Ocean, the plant’s operator TEPCO has admitted.

Follow RT’s LIVE UPDATES on Fukushima leak emergency

The Tokyo Electric Power Company (TEPCO), which is responsible for decommissioning the damaged Fukushima Daiichi nuclear plant, on Saturday said the protective barriers that were installed to prevent the flow of toxic water into the ocean are no longer coping with the groundwater levels, Itar-Tass reports.

The contaminated groundwater, which mixes with radioactive leaks seeping out of the plant, has already risen to 60cm above the barriers – the fact which TEPCO calls a major cause of the massive daily leak of toxic substances.

Earlier on Friday, the company announced it started pumping out contaminated groundwater from under Fukushima, and managed to pump out 13 tons of water in six hours on Friday. TEPCO also said it plans to boost the pumped-out amount to some 100 tons a day with the help of a special system, which will be completed by mid-August. This will be enough to seal off most of the ongoing ocean contamination, according to TEPCO’s estimates.

However, Japan’s Ministry of Industry has recently estimated that some 300 tons of contaminated groundwater have been flowing into the ocean daily ever since the March 2011 earthquake and tsunami that triggered the disaster.

TEPCO also promised it will urgently reinforce the protective shields to keep radioactive leaks at bay. The company has repeatedly complained it is running out of space and has had to resort to pumping water into hastily-built tanks of questionable reliability, as more than 20,000 tons of water with high levels of radioactive substances has accumulated in the plant’s drainage system.

Water samples recently taken at an underground passage below the Fukushima nuclear plant showed extreme levels of radiation comparable to those taken immediately after the March 2011 catastrophe. The tested water, which had been mixing with ground water and flowing into the ocean, contained 2.35 billion Becquerels of cesium per liter – some 16 million times above the limit.

Related:

Why Are Sharks Swarming in Florida?

Blacktip sharks and spinner sharks migrate
past Florida's coastline each year.
CREDIT: Chris Alleaume / Shutterstock.com

Why Are Sharks Swarming in Florida?
Mar 7, 2013 | Live Science | Marc Lallanilla

Seeing one shark is enough to scare most swimmers out of the water. Seeing thousands of sharks in the water — and many leaping into the air as they hunt for prey — could be enough to keep a swimmer out of the water for life.

That's the scenario greeting beachgoers this week in Palm Beach County, Fla., where as many as 15,000 sharks are swarming in the area's warm shallow waters, the Palm Beach Daily News reports.

"They were practically right on the sand," lifeguard supervisor Craig Pollock told the Palm Beach Daily News. "They were frenzied and chasing bait all the way up to shore." Beaches around the area are now closed to swimmers.

Pollock identified the sharks as blacktip sharks (Carcharhinus limbatus) and spinner sharks (Carcharhinus brevipinna). Both species are renowned for leaping out of the water and "spinning" in the air as they search for the smaller fish that make up their diet.

"I saw something jump," Allen Ginsberg, a New Jersey visitor, told the Palm Beach Daily News. "It looked like the shape of a shark, but I didn’t believe it at first and thought it was a fish."

Shark swarms

The dense pods of sharks seen off Florida shores are nothing new: These swarms are part of an annual migration that carries the animals south to their winter feeding grounds, Steve Kajiura, a shark researcher with Florida Atlantic University, told TCPalm.com.

"Our data has shown that the bulk of the migration occurs in January and February," Kajiura said, "but it may be a little behind this year due to the warmer weather and water temperatures."

During the winter months, when shark migrations are at their peak, there may be as many as 1,000 sharks in a 0.4 square-mile area (1 square kilometer). According to Kajiura, someone swimming during the shark migration is, on average, just 60 feet (18 meters) from a shark. [The 10 Most Incredible Animal Journeys]

"It is surprising to think there may be a shark swimming 60 feet away from us, but they are not out to get us," Kajiura told TCPalm.com.

Several species of sharks go on long-distance migrations of thousands of miles, according to noted shark expert Mahmood Shivji, of the Save Our Seas Shark Center and Guy Harvey Research Institute, Nova Southeastern University.

"A few examples of long-distance migrating species are: tiger sharks, short-fin mako sharks, white sharks, basking sharks, oceanic whitetip sharks [and] blue sharks," Shivji, who is director of the institute, told LiveScience.

Mysterious migrations

Researchers, however, are not completely sure why these migrations occur. "It could be for mating or giving birth, but also for feeding (following their prey that also migrate), or simply that the water gets too cold for them in some places in the winter," Shivji said.

"We are starting to learn a fair amount about the migrations of a few species, such as tiger sharks, white sharks, mako sharks [and] salmon sharks," Shivji said. "But information on migrations of most shark species is still sparse."

Shivji's work includes animated interactive websites that let the public track migrations of species such as tiger sharks in the Atlantic Ocean and mako sharks near New Zealand.

The blacktip and spinner sharks seen near Palm Beach County beaches don't usually target humans, though a handful of shark attacks have occurred. Florida reports the most shark bites of any U.S. state each year — 26 were reported in the state in 2012, according to the University of Florida's International Shark Attack File, and none of the bites were fatal.

"Shark attack as a phenomenon is extremely uncommon, considering the millions of hours humans spend in the water each year," said George Burgess, director of the International Shark Attack File.

Thirty million to 70 million sharks are killed every year in fisheries, Burgess noted, and humans pose a far greater threat to sharks than sharks do to humans.

"Because of their low rate of reproduction, [sharks] cannot keep up with the heavy fishing pressure encountered, and populations of many shark species have declined tremendously worldwide," Shivji said. "Understanding how they 'work,' including migrations, is essential to implementing effective management and conservation [practices] to prevent further declines."