joi, 18 septembrie 2008

'Day-Glo' Fish Shine Red Light

Seeing Red
- It was staring them in the face, but somehow generations of marine biologists have failed to notice that a lot of fish in the sea glow a fluorescent red, according to a study published Monday.

This unheralded talent for neon-like crimson displays is more than a curiosity, and is sure to create waves -- and a bit of embarrassment -- among ichthyologists, as fish experts are called.

It has long been axiomatic that red light is simply not part of the mental universe of marine fish because the sunlight's longest visible wavelengths do not penetrate below a depth of 30 feet.

A fire-engine red diving suit at 65 feet, for example, will appear dark grey or black to anyone -- or any fish -- that happen to be in the vicinity.

Dive far enough beneath the surface, and there is simply no red to be seen.

This foreshortening of the color spectrum under the waves was also assumed to correspond to a narrowed field of vision in fish, said the study's lead researcher in an interview.

"The general consensus, which dominated fish literature for 20 or 30 years, was that fish don't see red very well or at all," explained Nico Michiels, a researcher at the University of Tubingen in Germany.

From an evolutionary standpoint, in other words, why develop a skill that you will never be able to use?

But conventional wisdom, it seems, was flat-out wrong.

"We have been blinded, literally, by the blue-green light that is available on reefs in the daytime," said Michiels.

At least 32 species of reef fish -- including pygmy gobies and some wrasses -- can shine like a red Christmas bulb, not by reflecting sunlight but by emitting their own, the study found.

Dissection revealed that the fluorescence originates in guanine crystals, a chemical compound that is added to nail polish and car paint to give added luster.

And because the light is coming from the fish themselves, it remains visible at depth and is easily seen -- but only at close distances.

Michiels and his colleagues saw the light, as it were, by accident.

Looking through a filter while scuba diving that blocked out the brighter green and blue light waves, leaving only red ones, they suddenly saw a whole universe of sea creatures glowing various hues of cherry, crimson, ruby and rust.

"Besides fish, there are lots of fluorescent organisms on the reef, including algae, coral and other small organisms," Michiels said.

That some fish glow is certain, and was confirmed using spectrometry in laboratory experiments. It is also very likely that many can see red perfectly well, and do so for a reason.

One possibility is that they emit the color -- visible only within a small circumference -- as a means of intimate communication, perhaps for mating or to signal danger.

There is also evidence that turning red could serve as a kind of camouflage.

"It may seem strange, using fluorescence to make yourself invisible," Michiels said. "But fish that sit on a reef have a lot of fluorescence around them, so they blend in."

The next step is to figure out how day-glo fish might use their color-generating power to exchange information. Adapting techniques proven in other experiments with fish, Michiels is creating an environment in which fish can court each other via video.

By controlling which part of the color spectrum the fish can see, the researchers will seek to verify that some fish do, indeed, see red.

luni, 15 septembrie 2008

Antarctic Krill Found at Crushing Depths

Hearty Prey
Hearty Prey
- Scientists have discovered Antarctic krill living and feeding at crushing depths of 3,000 meters (9,800 feet) in waters around the Antarctic Peninsula, according to a study released Monday.

Until now the shrimp-like crustaceans were thought to only live within several hundred meters (yards) of the ocean surface, the study said.

The discovery radically changes the scientific understanding of the major food source for marine animals including fish, squid, penguins, seals and whales, said the study, published in the journal Current Biology.

"Most krill make their living in the ocean's surface waters," said Andrew Clark of the British Antarctic Survey.

"It was a surprise to observe actively feeding adult krill--including females that were apparently ready to spawn--close to the seabed in deep waters."

Antarctic krill feed on tiny phytoplankton and live in schools, called swarms, sometimes reaching densities of 10,000 individuals.

A key link in the Antarctic food chain, they grow to lengths of six centimeters (2.4 inches) and weigh up to two grams (0.7 ounces). They have a lifespan of up to eight to ten years.

Researchers from the British Antarctic Survey and the National Oceanography Center in Southampton used a deep-diving, remotely operated vehicle to film the krill in the nearly pitch-black depths.

Antarctic Warming Creating Predator 'Smorgasbord'

Headed South?

- Global warming is setting the stage for an invasion of predators on the sea floor around Antarctica, the likes of which have not been there for more than 40 million years.

Back in the late Eocene epoch, predatory animals such as sharks and crabs were driven away from Antarctic depths when the continent and its surrounding waters turned into an icebox, said researchers on Friday at a symposium at the meeting of the American Association for the Advancement of Science in Boston.

The result was a virtually predator-free zone on the seafloor and a paradise for worms, sea lilies, clams, brittle stars and other bottom-dwelling animals.

All that is about to end, however. Global warming is now raising water temperatures to the point where, very soon, those long-exiled predators could return and wreak havoc on the ocean floor, say biologists.

"It's going to be a smorgasbord," said researcher Cheryl Wilga of the University of Rhode Island. She studies the metabolic limitations of sharks that have kept them from Antarctic waters for millions of years, but may not do so much longer.

"The species in the Antarctic (seafloor) have no defense for shell-crushing predators," said extreme species researcher Brad Seibel, also of the University of Rhode Island. "I don't think that anyone was really aware of this issue."

Along the Antarctic Peninsula, the northernmost, warmest part of the continent, global warming is raising air temperatures quickly. Water temperatures have been warming as well, at a rate of about 0.04 degrees Celsius per year, Wilga says. That comes to about one degree per 25 years.

Compared to the relative stability seen for tens of millions of years, that's incredibly fast. Already, crabs are showing up, and some sharks are poised to pounce once the thermal dinner bell rings.

Antarctic King Crab?

The first exiled predator to return to Antarctica is the king crab. The leggy crustaceans have been found way down on the deep slopes off the Antarctic continental shelf -- where the water is slightly warmer than elsewhere.

There they are fighting the cold, explained marine scientist Richard Aronson of Dauphin Island Sea Lab and the University of South Alabama.

The frigid water makes it hard for the crabs to efficiently flush magnesium out of their bodies, said Aronson. Too much magnesium acts like a narcotic on a crab.

"When it's too cold, the magnesium makes them pass out and die," Aronson said. That's probably why the crabs have been absent for eons. Now, however, in those slightly warmer depths off the continental shelf, it's just warm enough for the crabs to survive there.

As the upper waters continue to warm, nothing will stop the king crabs from moving up onto the continental shelf and feasting. That will "hammer" the old seafloor communities, Aronson said.

"We expect the populations (of seafloor invertebrates) to take a dive," said Aronson.

Giant Starfish, Lilly Fields Found in Antarctic Waters

Well-Fed Starfish

- Scientists who conducted the most comprehensive survey to date of New Zealand's Antarctic waters were surprised by the size of some specimens found, including jellyfish with 12-foot tentacles and 2-foot-wide starfish.

A 2,000-mile journey through the Ross Sea that ended Thursday has also potentially turned up several new species, including as many as eight new mollusks.

It's "exciting when you come across a new species," said Chris Jones, a fisheries scientist at the U.S. National Oceanic and Atmospheric Administration. "All the fish people go nuts about that -- but you have to take it with a grain of salt."

The finds must still be reviewed by experts to determine if they are in fact new, said Stu Hanchet, a fisheries scientist at New Zealand's National Institute of Water and Atmospheric Research.

But beyond the discovery of new species, scientists said the survey, the most comprehensive to date in the Ross Sea, turned up other surprises.

Hanchet singled out the discovery of "fields" of sea lilies that stretched for hundreds of yards across the ocean floor.

"Some of these big meadows of sea lilies I don't think anybody has seen before," Hanchet said.

Dolphin Rescues Stranded Whales

Stranded? Try Me
Stranded? Try Me

- A dolphin guided two stranded whales to safety after human attempts to keep the animals off a New Zealand beach failed, a conservation official said Wednesday.

"I've never heard of anything like this before, it was amazing," Conservation Department officer Malcolm Smith said.

The actions of the dolphin, well known locally for playing with swimmers at Mahia beach on the east coast of the North Island, probably meant the difference between life and death for the whales, Smith said.

Smith had been working for over an hour and a half to save the two pygmy sperm whales which had repeatedly become stranded despite his attempts to push them back out to sea.

A bottlenose dolphin, named Moko by locals, appeared and guided the whales to safety after apparently communicating with them, Smith said.

The whales, a 10-foot female and her male calf, were apparently confused by a sandbar just off the beach and could not find their way back to open water.

Smith had been alerted at daybreak on Monday by a neighbor about the two stranded whales on Mahia beach near his home.

"Over the next hour and a half I pushed them back out to sea two or three times and they were very reluctant to move offshore," Smith said.

"I was starting to get cold and wet and they were becoming tired. I was reaching the stage where I was thinking it's about time to give up here, I've done as much as I can."

In that situation, whales are often humanely killed to end their suffering.

Smith said Moko arrived on the scene and he could hear the whales and the dolphin making noises, apparently to one another.

"The whales made contact with the dolphin and she basically escorted them about 200 yards parallel with the beach to the edge of the sandbar.

"Then she did a right-angle turn through quite a narrow channel and escorted them out to sea.

"There's been no sign of the whales since Monday, they haven't re-stranded."

"What the communication was I do not know, and I was not aware dolphins could communicate with pygmy sperm whales, but something happened that allowed Moko to guide those two whales to safety."

Moko has become famous for her antics at Mahia, which include playing in the surf with swimmers, approaching boats to be patted and pushing kayaks through the water with her snout.

Such close interaction with humans is rare among dolphins but not unknown. "She's become isolated from her pod obviously for one reason or another, but obviously made Mahia home just at the moment."

Mahia gets up to 30 whale strandings a year, most of which end with the whales having to be put down.

"I don't know if next time we have a whale stranding we can get her to come in again. She certainly saved the day for us and the whales this time."

North American Fish Under Threat

Keen SniffersaPacific Salmon
Pacific Salmon | Video: Discovery Earth

- Nearly 40 percent of fish species in North America are imperiled, according to a new survey by fish experts, the U. S. Geological Survey, and the American Fisheries Society, up 92 percent from the last survey done in 1989.

North America hosts perhaps the greatest diversity of temperate freshwater organisms on Earth, including aquatic insects, mussels, crayfish and fish.

The new report, compiling assessments from fish experts in the United States, Canada and Mexico, found that of the 700 types of fish in the survey, 230 are "vulnerable," 190 are "threatened," 280 are "endangered," and 61 are believed extinct.

"A lot of effort has been expended since 1989, but things are still in a sorry state in many ways," said study author Eric Taylor of the University of British Columbia in Vancouver. "We can't be complacent with trying to address some of these declines."

No single cause explains the ongoing fish losses, Taylor and others agree. Habitat loss, invasive species, diseases, dams, and water contaminants all contribute.

"Fish are kind of canaries in the coal mine," said Howard Jelks of the USGS and lead author of the report, published in Fisheries. "If you change the water to something that's not able to support these fish, it's also not going to be as high quality for recreating, for eating the fish out of these streams, for drawing water that's ultimately used for drinking, or for other things."

Certain regions were identified as hotspots with both high fish diversity and high degrees of threat. These included the Pacific central valley, the western Great Basin, the Rio Grande, and several river systems in the southeast such as the Tennessee and Mobile.

Pacific Coast salmon and trout were among the most at-risk types of fish, as were minnows, suckers, and catfish across the continent. Almost half of the carp and minnow family and the family of fish including perch and darters were identified in one of the imperiled categories.

The new report lists distinct sub-populations of certain fish separately, even if they are classified as the same species, which accounts for part of the increase.

joi, 11 septembrie 2008

Fish to Be Trained to Jump Into Nets

Jump, Roll Over

- Call them Pavlov's fish: Scientists are testing a plan to train fish to catch themselves by swimming into a net when they hear a tone that signals feeding time.

If it works, the system could eventually allow black sea bass to be released into the open ocean, where they would grow to market size, then swim into an underwater cage to be harvested when they hear the signal.

What's next, teaching them to coat themselves in batter and hop inside a fryer?

"It sounds crazy, but it's real," said Simon Miner, a research assistant at the Marine Biological Laboratory at Wood's Hole, which received a $270,000 grant for the project from the National Oceanic and Atmospheric Administration.

Miner said the specially trained fish could someday be used to bolster the depleted black sea bass stock. Farmed fish might become better acclimated to the wild if they can be called back for food every few days.

The bigger goal is to defray the costs of fish farming, an increasingly important source of the world's seafood. If fish can be trained to return to the farmer after feeding in the open ocean for several days, farms could save money on feed and reduce the amount of fish waste released in concentrated areas.

The key question for fish farmers: How many fish will actually return, and how many will be lost to predators or simply swim away?

Randy MacMillan, president of the National Aquaculture Association, said fish farmers won't be easily convinced to adopt open-ocean ranching.

"The commercial side is going to be skeptical," said MacMillan, who works on a trout farm in Idaho.

The Massachusetts project is one of several experiments funded by the federal government last year as part of aquaculture research.

"We're looking for innovations that will actually make a difference for coastal communities and the environment," said Michael Rubino, manager of NOAA Aquaculture. "It fits in both."

Previous experiments have used sound to train a fish to feed -- similar to what Russian scientist Ivan Pavlov did in his famous dogs that salivated at the sound of a bell, expecting food.

In Japan, scientists have used sound to keep newly released farmed fish in certain areas, where they could be caught in traditional ways.

But no one has ever tried to get fish to leave and return to an enclosure where they can be scooped up.

The project began last summer using 6,500 black sea bass, a stout, bottom-dwelling fish found between Florida and Cape Cod that migrates south of New Jersey in the winter. The species grows up to 3 pounds and 20 inches long and has a thick, white flesh that can be filleted for broiling or cut into nuggets for frying.

Miner said the first objective was to see if the fish could truly be trained. He got his answer after keeping the fish in a circular tank, then sounding a tone before he dropped food in an enclosed "feeding zone" within the tank that the fish could enter only through a small opening.

Researchers played the tone for 20 seconds, three times a day, for about two weeks. Afterward, whenever the tone sounded, "you have remote-control fish," Miner said.

"You hit that button, and they go into that area, and they wait patiently," he said.

Miner is now trying to figure out how long the fish remember to associate the tone with food. He feeds the fish outside the feeding zone without a tone for a few days and then tests if they will still head for the feeding area when the tone sounds again.

Sea Cucumber Inspires Nano-Material

One Bendy Critter
One Bendy Critter

Scientists have created a breakthrough substance that can change in seconds when exposed to liquid, shifting from hard plastic to soft and back again, and that has a wide range of potential medical applications.

The material -- inspired by the skin of sea cucumbers -- has astounding "mechanical morphing characteristics," according to an article published in the latest issue of Science.

Researchers said a plethora of possible biomedical applications exist for the malleable new material, including as part of "artificial nervous systems" for patients with Parkinson's disease, stroke or spinal cord injuries.

Sea cucumbers, found on ocean floors around the world, have leathery skin, an elongated, cucumber-like shape, and a consistency that can be either gelatinous, stiff and rigid, or anything in between.

This "switching effect" in the tissue of the sea cucumber is derived from a distinct nanocomposite structure in which highly rigid collagen nanofibers are embedded in a soft connective tissue.

Now the school of engineering at Case Western Reserve University and researchers at the Louis Stokes Cleveland Department of Veterans Affairs Medical Center have succeeded after years of effort in mimicking the unusual architectural structure of the sea creatures.

Colossal Squid Dissection Reveals Toothfish Diet

Big, Hungry Squid

Big, Hungry Squid

- Scientists examining the world's largest known colossal squid this week could find nothing in the cephalopod's stomach, suggesting the large marine animal was starving when it was captured in February of 2007.

That might help to explain why the squid was caught in the first place. The huge, jelly-like animal from Antarctica was voraciously eating an Antarctic toothfish hooked in a New Zealand long-line fishing operation in the Ross Sea when fishermen hauled up their catch, revealing the then half-dead, enormous squid.

View a slideshow of the colossal squid here.

The fishermen netted the squid and placed it in their vessel's freezer. It remained frozen until last week, when scientists at The Museum of New Zealand Te Papa thawed and analyzed the squid. Part of that investigation involved the insertion of an endoscope into the specimen's stomach.

"The endoscope revealed nothing," museum spokesperson Jane Keig told Discovery News. "Its stomach was empty."

Last week, the squid project's director, Carol Diebel, told Discovery News there were plans to remove tissue samples from the squid's stomach, but the researchers instead decided not to cut into the colossal squid, as "any kind of dissection could harm it" before the squid goes on public display in a specially constructed fluid-filled tank.

The Colossal Squid's Favorite Food

Diebel and her team instead focused their dissection efforts on yet another colossal squid housed in the museum. This second squid was laid out on a trough-like table next to the primary specimen for much of the week.

The stomach of that second squid yielded the remains of toothfish. Prior studies of colossal squid remains found in the stomachs of whales also revealed evidence of toothfish consumption, so scientists believe this fish could comprise a large portion of the colossal squid's diet.

The word "toothfish" generally refers to two closely related species: the Patagonian toothfish, popularly known as Chilean sea bass, and Antarctic cod, which is sometimes referred to as Antarctic toothfish. Both species possess a rather toothy, gaped mouth, hence the name, and can grow to around 7 feet or more in length.

Recently it was determined that the Antarctic toothfish possesses special proteins in its body that act like anti-freeze, preventing its blood from freezing into a solid block in the ice-laden, high latitude waters where it lives. Both the toothfish and the colossal squid favor deep water, 3,000 or more feet below the surface, and each has developed special adaptations to live and hunt in the darkness of that environment.

Hunting in the Dark

During this week's colossal squid investigation, the researchers were able to get an up-close look at the squid's tentacles. The tentacle tips -- appropriately called "clubs" -- are armed with two rows of sharp hooks that can swivel in all directions.

While no one has closely observed a colossal squid in hunting action, it's believed the animal moves quickly, grabbing toothfish and other prey with these spiked tentacles, which ironically somewhat resemble long-line fishing lines.

The scientists also discovered the squid has basketball-sized eyes, "the largest known in the animal kingdom," according to Diebel, along with a light organ right near the eye sockets. She believes this organ may function like a searchlight.

Toothfish also possess special eyes, with retinas that are well adapted to low light levels. While the mostly clear squid is nearly invisible in deep water, it's probable that colossal squid and toothfish play a continual hide and seek game of survival, where who spots whom first determines which one could live another day.

The Big Beak's Bite

The defrosted colossal squid's beak suggests the animal was much larger than it is now, a fact that's been supported by the men who witnessed the squid before it went into the freezer. Due to water and temperature changes, the squid shrunk to around 14 feet in length. Despite such alteration of the squid's flesh, its beak remains fully intact.

Among the colossal squid's many mysteries has been: How can an animal the consistency of firm Jell-O bite into prey without tearing itself to pieces?

Australia Shark Count Breaking Records

Topping the List

Topping the List

- Australians apparently have a good chance of spotting a shark in the wild, since a new project called the Great Australia Shark Count has thus far determined at least 4,022 sharks swim in waters surrounding the land down under.

While that figure is expected to rise as the count continues, the project has already broken records and is now considered to be the world's largest community shark count, Michael Rupnik, the project's executive officer, told Discovery News.

Prior contenders for that title were the award-winning Ecocean whale shark project, which has reported 1,100 shark sightings in over 10 years, and the global Shark Trust, which has had about 200 shark sightings since 1997.

Adam Smith, national chair of the Australian Underwater Federation that is overseeing the count, credits its success to two reasons.

"Firstly, we have lots of sharks in Australia and people love getting in the water and diving and fishing," he said, adding that Australians also possess "a thirst for knowledge and want to make a difference."

Count participants include scuba divers, underwater spear fishermen and many other recreational water users.

While the project will continue throughout the year, the current most reported shark is the wobbegong, with 903 sightings. The grey nurse shark follows, with 733, and Port Jackson sharks round out the top three with a count of 519.

Other commonly spotted sharks include the grey reef shark, the whitetip reef shark, whale sharks, the blacktip reef shark, the tiger shark, gill sharks and the toothy great white. So far, participants have recorded 13 great white sightings.

U.S. Shark Bill Targets Finning Loopholes

Maximum Profit
Maximum Profit
After the U.S. House of Representatives subcommittee hearings last month, a new shark bill promising to close disturbing loopholes in existing shark fishing regulations has inched a step closer to becoming law.

The bill, entitled The Shark Conservation Act of 2008, specifically addresses the problem of finning, or removal of a shark's fins for shark fin soup, folk remedies and other forms of consumption.

Because of this practice, shark fins are among the world's most valuable fishing products, but the real price is that sharks are further threatened with extinction, since the marine predators usually die once their finless bodies are tossed overboard.

Sharks are also a slow-growing fish, with some species producing few pups, so recovery from over-fishing is next to impossible.

"The Shark Conservation Act of 2008 reestablishes the intended protections for sharks under U.S. law," said Congresswoman Madeleine Bordallo (D-Guam), who is Chairwoman of the Subcommittee on Fisheries, Wildlife and Oceans.

"I look forward to working with my colleagues on both sides of the aisle to advance this timely and important bill," she added.

Existing Loopholes

Bordallo explained that the bill attempts to close at least three loopholes. The first addresses the difficulty of enforcing "fin to carcass" ratios aboard vessels. Under current regulations, many fishermen can collect fins, so long as a comparable weight of shark bodies accompanies them.

"It has proven virtually impossible, however, to determine whether a given set of fins belong to a particular dressed carcass," she said. "As a result, there are reports of fishermen mixing fins and carcasses for maximum profit, continuing to discard less desirable, finned sharks at sea."

Humpback Whales Make Huge Comeback

They're Back

Once hunted to the brink of extinction, humpback whales have made a dramatic comeback in the North Pacific Ocean over the past four decades, a new study says.

The study released Thursday by SPLASH, an international organization of more than 400 whale watchers, estimates there were between 18,000 and 20,000 of the majestic mammals in the North Pacific in 2004-2006.

Their population had dwindled to less than 1,500 before hunting of humpbacks was banned worldwide in 1966.

"It's not a complete success, but it's definitely very encouraging in terms of the recovery of the species," said Jeff Walters, co-manager of the Hawaiian Islands Humpback Whale National Marine Sanctuary.

The study, sponsored by the National Oceanic and Atmospheric Administration, is the most comprehensive analysis ever of any large whale population, said David Mattila, science coordinator for the sanctuary.

At least half of the humpback whales migrate between Alaska and Hawaii, and that population is the healthiest, Mattila said.

But isolated populations that migrate from Japan and the Philippines to Russia are taking a longer to recover after whaling operations ceased, he said.

"Whales are long-lived and give birth one at a time .... so if the population gets pushed too low, it may take quite awhile to come back. Maybe that's what's happening in the west," Mattila said.

The whales are protected under federal laws that include the Marine Mammal Protection Act and the Endangered Species Act.

duminică, 7 septembrie 2008

Colossal Squid's Size Key to Survival

Big, For Good Reason

Big, For Good Reason

- The frozen colossal squid that was thawed this week shrank drastically due to water and temperature changes since it was accidentally caught by fisherman in 2007, according to officials at The Museum of New Zealand Te Papa who revealed the exact size of the squid on Thursday and believe it is still the world's largest known squid.

View a slideshow of the colossal squid here.

After waiting for the tentacles to defrost so the squid could be fully extended, the researchers measured its weight at 1,091 pounds and its length at nearly 14 feet.

The squid's heft and large beak "confirm that it was almost certainly longer and is still the largest invertebrate specimen in the world," Te Papa spokesperson Jane Keig told Discovery News.

She added that it also has the largest eye of any animal at about 10.5 inches in diameter.

Other Ocean Giants

Colossal squids exemplify a phenomenon known as deep-sea gigantism, which is the tendency for invertebrates, crustaceans and other creatures of the deep to grow to become much larger than their shallower water counterparts. Some squid, in contrast to the colossal, are just a few inches long.

Dutch biologist Olaf Blaauw, who traveled to New Zealand to analyze the enormous squid, told Discovery News that whales serve as other obvious examples of gigantism. Sharks may grow to extreme lengths too.

"A whale shark can attain a length in excess of 45 feet," he said. "Basking sharks get over 30 feet…There are probably deep water shark species yet undiscovered, based on anecdotal evidence and further strengthened by the discovery of the 15-feet megamouth shark relatively recently."

He added that ocean sunfish also grow to be very large at 10 feet long and high, and weighing up to 2 tons -- "probably the heaviest bony fish around."

Another possible member of the colossal group is the giant leatherback sea turtle, which can grow to around 8 feet in length and weigh close to a ton. Japanese spider crabs and oarfish (a type of herring) also exhibit gigantism, along with other types of squid and octopi.

Why So Big?

From a Darwinian fitness perspective, "if any attribute favors survival, it will be preserved in a species until circumstances change to make another random change in shape, form or behavior more favorable," Blaauw said.

The size of these deep-sea monsters therefore somehow improves their longevity and rate of survival.

One obvious reason is that a big body can be intimidating to other animals.

"Suffice it to say, there is little out there that can tackle a thousand-pound squid armed to the beak with powerful arms, each lined with vicious hooks and suckers," Blaauw said.

Aside from humans, the colossal squid's only other natural enemies are the occasional large shark and sperm whales, which seem to have a real taste for the cephalopod giants because they hunt them voraciously. Researchers aren't even certain that a shark can actually kill a colossal squid. Large squid remains have been found in shark stomachs, but it's possible the sharks just scavenged their already dead remains.

Size Affects Eating

Whether on land or in the ocean, an animal's size appears to predict how and what it eats. Scientists first began to make this correlation after they noticed that particularly large creatures are more vulnerable to habitat changes than smaller animals are.

John Haskell of Utah State University and his colleagues developed a computer model to explain why that's the case. They discovered the way an animal forages can be directly linked to its length and weight.

"What we found is that an organism's body size is a key determinant of how often it can be expected to encounter food in its environment," Haskell said. "Resource density is often scale-dependent, that is it changes with the scale of measurement. The food density you see at one square meter changes when you zoom out to one square kilometer."

In essence, a tiny squid looks at the world a few inches at a time, while a colossal squid must look at potentially miles at a time, perhaps somewhat explaining its gigantic eyes. Prey appears to be more sparse and patchy for larger animals, which need to cover expansive territories to get their fill.

If predictions made by Haskell's model hold up, the more the colossal squid's habitat becomes fragmented, the larger its home range will become, potentially causing the squid to grow even larger and to travel longer and longer distances for food.

Shark Attack Kills San Diego Man

After the Attack

After the Attack

- A shark on Friday attacked and killed a 66-year-old swimmer who was training in the ocean off San Diego County with a group of triathletes, authorities said.

The man was attacked by what authorities believe was a great white shark at Tide Beach around 7 a.m., authorities said.

The man, a local resident whose identity was not immediately released, was taken to a lifeguard station for emergency treatment but was pronounced dead at the scene, according to a statement on the Solana Beach city Web site.

The man's injuries crossed both thighs and were made "by what is probably a great white shark," San Diego County sheriff's Sgt. Randy Webb said in a statement.

"It looks like the shark came up, bit him, and swam away," said Solana Beach Deputy Fire Chief Dismas Abelman.

The attack took place about 150 yards offshore. Several swimmers wearing wetsuits were in a group when the shark attacked, said Solana Beach lifeguard Craig Miller. Two swimmers were about 20 yards ahead of the man when they heard him scream for help. They turned around and dragged him back to shore.

Swimmers were ordered out of the water for a 17-mile stretch around the attack site and county authorities sent up helicopters to scan the waters for the shark.

"The shark is still in the area. We're sure of that," Mayor Joe Kellejian said.

Rob Hill, a member of the Triathlon Club of San Diego, said he was running on the beach while about nine other members were in the water when the attack took place.

Shark Oil Contaminated by VCR Chemical

Hazardous to Your Health?

Hazardous to Your Health?

- A flame retardant found in everything from consumer electronics to furniture is contaminating waters where sharks swim and winding up in fish oils sold as nutritional supplements, according to a new study published in the journal Food Chemistry.

Scientists led by Kensaku Kakimoto of the Osaka Prefectural Institute of Public Health in Japan analyzed fish oils purchased from Japanese markets for the presence of the potentially toxic chemical hexabromocyclododecane (HBCD).

The researchers first chemically separated the oils into their basic ingredients, and then used mass spectrometry, a process that looks at charged particles, to identify the presence of HBCD.

They found it in 15 of the 22 samples. While concentrations varied, some sardine and shark liver oils from fish captured near Japan contained "relatively high levels of HBCD, indicating that both the surface and deep seawaters around Japan may have been contaminated," the researchers wrote.

It's unknown how the chemical wound up in the water, but an event as simple as someone dumping a VCR into a landfill could contribute to the problem, since rainwater could wash the chemical into oceans or the chemical could vaporize and enter the atmosphere, according to Tim Fitzgerald, an Environmental Defense Fund marine scientist.

Shark liver oil manufacturers don't always state what species the oil came from, but it is commonly derived from deep-sea sharks, dogfish sharks and basking sharks. As the name suggests, the oil is extracted from the livers, which can make up about 25 percent of the shark's total body weight.

Although certain chemicals in shark liver oil have been studied as immune system stimulants, there is little medical evidence to support some of the oil's purported health benefits, which range from treating radiation sickness to pimple breakouts to cancer.

Trapped Sea Lions Shot Dead

Sitting Ducks
Sitting Ducks

- For years, the sea lions lounging at the Bonneville Dam have had easy pickings from salmon waiting to go up fish ladders to upriver spawning grounds.

Over the weekend, the federally protected sea creatures were themselves easy prey for a gunman who shot and killed six of the sea lions as they lay in traps meant to humanely catch them.

State and federal authorities were investigating the shootings, which came less than two weeks after an appeals court issued a temporary injunction against authorities killing the salmon-gobbling mammals. Agents have been trapping them instead, but trapping will be suspended during the investigation, said Rick Hargrave, a spokesman for the Oregon Department of Fish and Wildlife.

Fishermen and American Indian tribes have pushed to protect the salmon and remove the sea lions, by lethal force if necessary.

The carcasses of the four California sea lions and two Steller sea lions were found Sunday around noon below the Bonneville Dam on the Columbia River on the border of Oregon and Washington.

The six animals appear to have been shot by somebody on the Washington side during the night, said Brian Gorman, a spokesman for the National Marine Fisheries Service.

Two open cages each contained the carcasses of two California sea lions and one Steller sea lion, he said.

Sharks Ruled Alabama's Dino-Era Waters

Goblin Shark Descendent
Goblin Shark Descendent

- The American South's golden age for sharks might very well have been the Cretaceous Era during the dinosaur age, according to tooth remains found for a number of different species.

Most recently, the teeth of Scapanorhynchus texanus, also known as the "goblin shark of Texas," were found and dated to between 78.8 and 79.2 million years ago

The teeth were recovered from what is now a vertical cliff next to a creek in western Alabama. The spot was once a seabed below waters teaming with unusual looking fish, including the now-extinct shark.

"Judging from the abundance of shark teeth preserved in the Cretaceous of Alabama, sharks were abundant in Alabama seas during the Cretaceous," Martin Becker, who led the project, told Discovery News.

"Shark teeth are also abundant, however, in Cretaceous deposits of the Gulf Coast and the Atlantic coastal plain, so it's pretty clear that they were abundant up and down the coast of what is now the United States," added Becker, an associate professor of environmental science at William Paterson University.

Becker and colleagues David Seidemann, John Chamberlain, Dieter Buhl and William Slattery studied 15 fossil shark teeth from the vertical cliff created by Trussels Creek in Greene County, Ala. Although the researchers focused on the goblin shark specimen, also nicknamed "spade snout," they believe some of the teeth belonged to different sharks because the deposit concentrated materials coming from various parts of a seabed.

They cut slices of the teeth to study its three different types of tissues: the orthodentine and osteodentine, which form the pulp cavity and root structure of a tooth, and the enameloid, which is the hard outer surface.

The scientists then determined the strontium isotope composition of each of the different types of tooth tissue. Strontium isotopes have a radioactive component that increases incrementally over time as the result of decay. When compared with the non-changing part of the metal's atoms, scientists can date tooth fossils.

They can also reconstruct past environments, since the chemical composition of the teeth usually locks in certain isotopic signatures of the seawater in which the shark lived.

The findings have been accepted for publication in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

The researchers discovered that tooth enamel provided far more accurate data than the other parts of the tooth, suggesting that future studies should focus only on the hard enamel surfaces.

"We expect that enamel in any creature would be less susceptible to alteration after its formation than the other dental tissues, probably because enamel is well-crystallized and not as porous as dentine," explained Seidemann, a Brooklyn College geochemist.

joi, 4 septembrie 2008

Shark Fin Demand Pushes 11 Species Near Extinction

Heavy Price
Heavy Price
Overfishing driven in part by an insatiable appetite for shark-fin soup has threatened 11 species of the ocean-dwelling predators with extinction, according to a report released on Thursday.

The first study to assess the worldwide status of 21 species of pelagic sharks and rays -- those living and hunting in open seas -- found that more than half are rapidly being fished out of existence.

Particularly vulnerable species include the short-finned mako, the thresher and the silky, said the report, to be published in the journal Aquatic Conservation: Marine and Freshwater Ecosystems.

"Despite mounting evidence of decline and increasing threats to these species, there are no international catch limits for oceanic sharks," said co-author Sonja Fordham, a researcher at the Oceans Conservancy and Shark Alliance in Brussels.

"Our research shows that action is urgently needed on a global level if these fisheries are to be sustainable."

Many big shark species have fallen prey to booming Asian economies where shark-fin soup is prized as a must-have delicacy at weddings and other banquet occasions. The fins are often sliced off of living fish which are then discarded in the sea.

Accidental "by-catch" by industrial fishing operations have also decimated shark populations, the study said.

Sharks and big rays are especially vulnerable to overfishing because they take many years to reach sexual maturity and have relatively few offspring.

"We are losing species at a rate 10 to 100 times greater than historic rates," said the study's lead author, Nicholas Dulvy, a professor at Sime Fraser University in Vancouver, Canada.

The report, presented at a major UN conference on biodiversity in Bonn, calls for the establishment and enforcement of science-based catch limits for sharks and rays, and a ban on the practice of "shark finning."

The 11-day Bonn conference seeks to prevent the destruction of countless plant and animal species.

It is the ninth of its kind of countries who signed up to the UN Convention on Biological Diversity at the 1992 Rio Earth Summit.

Oldest Live Birth Captured in Fish Fossil

"Mother Fish"
- She is the oldest mother of any species ever found, a 380-million-year-old fish immortalized in a fossil while still attached to her offspring by an umbilical cord.

Dubbed "mother fish" by the scientists who discovered her in northwestern Australia, Materpiscis attenboroughi is not only an entirely new genus and species, but pushes back the first known case of live birth in the animal kingdom by some 200 million years.

The tail-first birthing process was probably similar to that of some species of sharks and rays living today, says the study, published Thursday in the British journal Nature.

"The discovery is certainly one of the most extraordinary fossil finds ever made, and changes our understanding of the evolution of vertebrates," commented lead researcher John Long, head of science at Museum Victoria.

Long and his colleagues were particularly astounded to find such a sophisticated reproductive system so far back on the evolutionary clock.

"It shows us that live birth was occurring at the same time as egg laying, and that these mechanisms evolved together rather than sequentially," explained co-author Kate Trinajstic, who together with Long found the fossil.

The existence of the embryo and umbilical cord within the specimen also provides the first-ever example of "internal fertilization" -- that is, sex with penetration, the study says.

About 10 inches long, "mother fish" belongs to an extinct group of vertebrates, known as placoderms, that thrived during Middle Palaeozoic Era some 420 to 350 million years ago.

Antarctic Mega-Iceberg Suffocates Seals

Weddell Seals
Life Before the Berg
Weeks after the controversial listing of polar bears as threatened species, new research graphically demonstrates how changes to polar ice can devastate local animals.

The findings of a grim new study illustrate the direct, and often immediate, effects that climate change can have on the physiology, behavior and survival of wild species.

An Iceberg the Size of Rhode Island

In 1998, ecologist and evolutionary biologist Terrie Williams of the University of California at Santa Cruz and her team began a study on Weddell seals in Antarctica.

Three years later, an enormous iceberg detached near Antarctica's McMurdo Sound. According to Williams and her colleagues, the event was caused by global warming, which has likely been melting and weakening ice at the poles.

The 4,200-square-mile iceberg -- dubbed B-15 -- drifted westward and lodged on nearby Ross Island. The lives of countless animals would soon forever change.

Seals Struggle for Breathing Room

"Our first clue that there was a problem was that the seals were not returning to their usual pupping areas, and that there were fewer seals even later in the season," Williams told Discovery News.

She and her colleagues noticed that the ice around Ross Island did not experience its usual "break-out" that year. Normally the ice thaws, creating thinner areas where diving seals can carve breathing holes in the ice shelf. Instead, the presence of B-15 thickened the surrounding ice.

"We started out with three feet of ice and were up to a nine feet thickness" by 2002, the last year of the study, Williams said.

Filming both above and below the thickened ice, Williams and her colleagues observed seals lining up to breathe at the few holes they were able to make with their front canine teeth. Lacking the energy to swim further, fights ensued in the lines, with animals lashing out at each other for access to air.

Williams explained that after B-15 dislodged, there were 80 miles of ice between McMurdo and the open ocean.

"Weddell seals can only swim four miles under ice before they have to come up to breathe, so you can see the problem," she said.

Physiological Systems Overtaxed

The researchers measured the oxygen consumption of seals that managed to surface, and by analyzing the underwater video, calculated the energy cost of each stroke the seals made during dives.

After comparing these calculations with prior data on seals diving under normal conditions, the researchers found that the new environment simultaneously increased the seals' need for oxygen and reduced their access to air.

Since seals dive to hunt, most were unable to catch enough prey to sustain themselves and their pups.

Fishing Nets Entangling Fewer Dolphins

The most recent dolphin counts in the eastern tropical Pacific Ocean suggest that two species decimated by deaths in tuna fishing nets may be making a comeback.

Populations of the northeastern offshore spotted dolphin and the eastern spinner dolphin plummeted by 80 and 70 percent, respectively, between 1960 and 1990, as they were caught in nets set for tuna. More than six million dolphins have died this way since the late 1950s.

Thanks to increasingly strong regulations to prevent these deaths passed in the 70s, 80s and 90s, dolphin deaths have declined drastically, with fewer than 1,000 dolphins now dying a year in nets.

"Because they were so good at reducing the mortality, we've been expecting the population to recover for quite some time now," said Jeremy Rusin, of the National Oceanic and Atmospheric Association's Southwest Fisheries Science Center in La Jolla, Calif.

It took longer than expected to see improvement, but the latest survey, conducted in 2006, estimates the northeastern offshore spotted dolphin population at 857,884, up from 822,157 in 2003, and 636,780 in 2000. NOAA estimated the eastern spinner dolphin population at more than 1.06 million in 2006, compared with 673,943 in 2003.

Although the counts show an increase, Rusin emphasized that the results do not indicate a conclusive trend. The large area covered by the survey -- almost the size of North America -- means the estimates carry large uncertainty.

"We need additional surveys to be sure that the increases we've seen this year are real increases, and not just the reflection of statistical uncertainty," Rusin said.

One group of dolphins, the western/southern spotted dolphins, continued to decline. This finding, coupled with the rise of the northeastern offshore spotted dolphin, may simply be explained by a migration of some individuals from one zone to another, Rusin said.

Fish 'Fly' Against Currents With Wing-Like Fins

Flying Parrotfish
Flying Parrotfish
- A team of researchers has found how some reef fish use their fins to fly underwater, allowing them to survive in the sometimes cyclonic currents surrounding coral reefs.

The research, led by Chris Fulton from The Australian National University, appears in the journal Coral Reef.

Fulton says he first noticed the wing-like fins during surveys of coral reefs in Australia.

"We were surveying different reef fish across different gradients on the Great Barrier Reef and we noticed that some of the ones that lived in the very shallow areas were very abundant -- lots of individuals of just a few species," Fulton said.

"When we looked at those few species in a bit more detail, we noticed something a bit unique about their fins -- a wing-shaped fin."

The wing shape allows fish such as parrotfish, wrasse and surgeonfish to fly through the water using a figure-of-eight pattern.

"Most fish when they move their pectoral fins on the side of their body, they move them just like you row a boat -- they have a power stroke and then a recovery stroke," Fulton says. "By doing that they are only creating thrust half the time."

He says fish with wing-shaped fins keep them spread at all times and sweep in a figure-of-eight pattern that constantly generates thrust.

"They do this by inclining their fins at just the right angle to create lift from the water flowing over the fin, similar to the way air moves over the wing of a bird to propel them through their air," Fulton said.

Fulton believes the extra push that the wing-like fins give the fish helps them survive in the shallow and sometimes turbulent waters surrounding coral reefs.

"They're dealing with waves crashing on to them all day, everyday, and those crashing waves create water motions that are extreme," he said.

"If you scaled up the differences in the thickness of water to the thickness of air ... it would be like us dealing with cyclone force winds everyday."

Chris and his colleagues, David Bellwood from James Cook University and Peter Wainwright from the University of California, Davis, observed the fish swimming around the reef and in flow tanks, which allowed them to record the fish's movement on high-speed video cameras.

"We set up a high-speed video, which records about 200 frames per second and we run them at different speeds in the tank and record the motion of their fins on the high-speed camera," he said.

They found some species could move at up to 10 body lengths per second. By comparison, Olympic champions reach speeds of just 1.3 body lengths per second, and then only for the brief 22 seconds of the 50-meter freestyle sprint.

Fulton says the U.S. Office of Naval Research has taken interest in the research, looking to use it in the development of future remote control submersibles.

"Things that we are learning from 50 million years of evolution have taught us that fish are a very good solution," he said.

But Fulton doesn't envisage Olympic swimmers using the winged-shaped technique in the near future.

"It may give us ideas for a new swimming stroke in a human, how to make fine adjustments in the swimming stroke at different speeds," he said. "But humans are constrained by our rather clumsy sort of limbs that aren't really made for water."

marți, 2 septembrie 2008

Bug-Eyed Flatfish Evolution Revealed

Left-Eyed Flatfish
Left-Eyed Flatfish
- Starting with Charles Darwin, evolutionary biologists have fretted and fought over the origins of flatfish, among the handful of weird, deeply asymmetrical creatures in Nature's bestiary.

Did flatfish wind up with two eyes on the same side of a lopsided skull through a few chance mutations?

Or did this happen gradually, over tens of millions of years?

The answer, in turns out, has been gathering dust for nearly two centuries in museum drawers, according to a study published Thursday in the British journal Nature.

That was where Matt Friedman, a graduate student at the University of Chicago, found two fossils that clearly show a glacial evolutionary shift from normal upright fish to their bug-eyed, bottom-hugging descendents.

Each dates from the Eocene epoch, some 45 million years ago, and one -- Heteronectus chaneti -- is an entirely new genus and species.

The other is from the Amphistium genus, whose earliest known specimens date back some 200 million years.

Both are true "missing links," with one eye just below the dorsal fin on the side of the fish closest to the ocean floor.

For reasons unknown to scientists, some species of modern flatfish, such as turbot, have both eyes on the left side, while other -- halibut and sole, for example -- see from the right side.

The two fossils "deliver the first clear picture of flatfish origins, a hotly contested issue in debates on the mode and tempo of evolution," said Friedman.

There can no longer be any doubt, he said in a statement: "The evolution of the profound cranial asymmetry of extant flatfishes was gradual in nature."

The flatfish controversy has vexed scientists for at least 150 years, and even provided fodder for creationist challenges to the very notion of Darwinian evolution.

All the great figures of early evolutionary biology weighed in with theories falling roughly into two schools.

The absence of any fossils showing a halfway point between normal fish and flatfish led some to believe that change took place in dramatic leaps, a process they called "saltation".

Others, including Darwin himself, predicted that we would one day find evidence of a gradual eye migration that mirrors the maturation of living forms.

When flatfish are only days old they are perfectly symmetrical.

But they rapidly metamorphose as they grow, with one eye migrating toward the other.

Neither of the key fossils rediscovered by Friedman had been examined with modern scientific tools for fear of causing damage.

But Friedman was finally allowed to treat a single specimen housed in the Naturhistorisches Museum in Vienna with a weak acid bath, and to carry out computer-based tomography imaging of the skull of another specimens at the Natural History Museum in London.

Both fossils had been found in limestone quarries in northern Italy.

Singing for Sex: Even Toadfish Do It

Everything But the Girl
Everything But the Girl
- It's not exactly Tony serenading Maria in "West Side Story," but for all their homeliness toadfish also sing to attract mates.

OK, singing may be a stretch; it's more of a hum. But it turns out to be useful, for science as well as the fish. Exploring how their nervous system produces sounds is allowing scientists to trace the earliest developments of vocalization in other animals, including people.

Many animals communicate vocally -- birds chirp, frogs thrum, whales whistle -- and comparing the nerve networks in a variety of vertebrates suggests that making sounds originated in ancient fishes, researchers report in Friday's edition of the journal Science.

The sounds of whales and dolphins are well known, but most people don't realize fish also make sounds, lead researcher Andrew H. Bass of Cornell University said in a telephone interview. He's a professor of neurobiology and behavior.

"I'm not saying fish have a language or are using higher powers of the brain," he added quickly. "But some of the networks of neurons, nerve cells in the brain, are very ancient."

The whole nervous system basis that led to speech originated in fish hundreds of millions of years ago, he said.

He studied the hindbrain in the larvae of midshipmanfish and toadfish, which grow up to produce more than one type of sound.

"It's not as complex as what you hear mammals and birds doing; it's the simplest type of communication ... but the parts of the nervous system that generate sounds are easiest to study in these fish," Bass said.

His team found two major uses of sound.

One is the hum in which the male sings to attract the female to his nest. Bass characterized it as like the drone of bees or a motor running.

The second type is a threat sound, more of a grunt or growl, to protect nesting territory.

The locations of the vocal nerves described in the study are consistent with the organization of the vocal systems in frogs, birds and mammals, supporting the idea of a common early development, Daniel Margoliash and Melina E. Hale of the University of Chicago comment in a perspective on Bass's study.

However, they add: "The story of the evolution of vocalizations is still being written, both for its deep ancestral roots and for its most modern development."

The research was funded by the National Science Foundation and the National Institutes of Health.