While filming coral off the Solomon Islands, David Gruber, a National Geographic Emerging Explorer, encountered a “bright red-and-green spaceship.” This underwater UFO turned out to be a hawksbill sea turtle, which is significant because it’s the first time that biofluorescence has ever been seen in reptiles, according to Gruber.
Gruber is now excited to learn more about this critically endangered species and how it is using biofluorescence.
Newly discovered fossils of a giant, extinct sea creature show it had modified legs, gills on its back, and a filter system for feeding — providing key evidence about the early evolution of arthropods.
The new animal, named Aegirocassis benmoulae in honor of its discoverer, Mohamed Ben Moula, attained a size of at least seven feet, ranking it among the biggest arthropods that ever lived. It was found in southeastern Morocco and dates back some 480 million years.
“Aegirocassis is a truly remarkable looking creature,” said Yale University paleontologist Derek Briggs, co-author of a Nature paper describing the animal. “We were excited to discover that it shows features that have not been observed in older Cambrian anomalocaridids — not one but two sets of swimming flaps along the trunk, representing a stage in the evolution of the two-branched limb, characteristic of modern arthropods such as shrimps.”
Briggs is the G. Evelyn Hutchinson Professor of Geology and Geophysics at Yale and curator of invertebrate paleontology at the Yale Peabody Museum of Natural History. First author Peter Van Roy, an associate research scientist at Yale, led the research; Allison Daley of the University of Oxford is co-author.
Since their first appearance in the fossil record 530 million years ago, arthropods have been the most species-rich and morphologically diverse animal group on Earth. They include such familiar creatures as horseshoe crabs, scorpions, spiders, lobsters, butterflies, ants, and beetles. Their success is due in large part to the way their bodies are constructed: They have a hard exoskeleton that is molted during growth, and their bodies and legs are made up of multiple segments. Each segment can be modified separately for different purposes, allowing arthropods to adapt to every environment and mode of life.
Modern arthropod legs, in their most basic form, have two branches. Each is highly modified to cater to a specific function on that leg, such as locomotion, sensing its surroundings, respiration, or copulation; or it has been lost altogether. Understanding how these double-branched limbs evolved has been a major question for scientists.
A long-extinct group of arthropods, the anomalocaridids, is considered central to the answer. The youngest known anomalocaridids are 480 million years old, and all of them looked quite alien: They had a head with a pair of grasping appendages and a circular mouth surrounded by toothed plates. Their elongate, segmented bodies carried lateral flaps that they used for swimming. Until now, it was believed that anomalocaridids had only one set of flaps per trunk segment, and that they may have lost their walking legs completely.
But the recent discovery of Aegirocassis benmoulae tells another story. The new animal shows that anomalocaridids in fact had two separate sets of flaps per segment. The upper flaps were equivalent to the upper limb branch of modern arthropods, while the lower flaps represent modified walking limbs, adapted for swimming. Furthermore, a re-examination of older anomalocaridids showed that these flaps also were present in other species, but had been overlooked. These findings show that anomalocaridids represent a stage before the fusion of the upper and lower branches into the double-branched limb of modern arthopods.
“It was while cleaning the fossil that I noticed the second, dorsal set of flaps,” said Van Roy, who spent hundreds of hours working on the specimens. “It’s fair to say I was in shock at the discovery, and its implications. It once and for all resolves the debate on where anomalocaridids belong in the arthropod tree, and clears up one of the most problematic aspects of their anatomy.”
Aegirocassis benmoulae is also remarkable from an ecological standpoint, note the researchers. While almost all other anomalocaridids were active predators that grabbed their prey with their spiny head limbs, the Moroccan fossil has head appendages that are modified into an intricate filter-feeding apparatus. This means that the animal could harvest plankton from the oceans.
“Giant filter-feeding sharks and whales arose at the time of a major plankton radiation, and Aegirocassisrepresents a much, much older example of this — apparently overarching — trend,” Van Roy said.
The above story is based on materials provided by Yale University. The original article was written by Jim Shelton. Note: Materials may be edited for content and length.
Vast ranges of volcanoes hidden under the oceans are presumed by scientists to be the gentle giants of the planet, oozing lava at slow, steady rates along mid-ocean ridges. But a new study shows that they flare up on strikingly regular cycles, ranging from two weeks to 100,000 years—and, that they erupt almost exclusively during the first six months of each year. The pulses—apparently tied to short- and long-term changes in earth’s orbit, and to sea levels–may help trigger natural climate swings. Scientists have already speculated that volcanic cycles on land emitting large amounts of carbon dioxide might influence climate; but up to now there was no evidence from submarine volcanoes. The findings suggest that models of earth’s natural climate dynamics, and by extension human-influenced climate change, may have to be adjusted. The study appears this week in the journal Geophysical Research Letters.
“People have ignored seafloor volcanoes on the idea that their influence is small—but that’s because they are assumed to be in a steady state, which they’re not,” said the study’s author, marine geophysicist Maya Tolstoy of Columbia University’s Lamont-Doherty Earth Observatory. “They respond to both very large forces, and to very small ones, and that tells us that we need to look at them much more closely.” A related study by a separate team this week in the journal Science bolsters Tolstoy’s case by showing similar long-term patterns of submarine volcanism in an Antarctic region Tolstoy did not study.
Volcanically active mid-ocean ridges crisscross earth’s seafloors like stitching on a baseball, stretching some 37,000 miles. They are the growing edges of giant tectonic plates; as lavas push out, they form new areas of seafloor, which comprise some 80 percent of the planet’s crust. Conventional wisdom holds that they erupt at a fairly constant rate–but Tolstoy finds that the ridges are actually now in a languid phase. Even at that, they produce maybe eight times more lava annually than land volcanoes. Due to the chemistry of their magmas, the carbon dioxide they are thought to emit is currently about the same as, or perhaps a little less than, from land volcanoes—about 88 million metric tons a year. But were the undersea chains to stir even a little bit more, their CO2 output would shoot up, says Tolstoy.
Some scientists think volcanoes may act in concert with Milankovitch cycles–repeating changes in the shape of earth’s solar orbit, and the tilt and direction of its axis—to produce suddenly seesawing hot and cold periods. The major one is a 100,000-year cycle in which the planet’s orbit around the sun changes from more or less an annual circle into an ellipse that annually brings it closer or farther from the sun. Recent ice ages seem to build up through most of the cycle; but then things suddenly warm back up near the orbit’s peak eccentricity. The causes are not clear.
Enter volcanoes. Researchers have suggested that as icecaps build on land, pressure on underlying volcanoes also builds, and eruptions are suppressed. But when warming somehow starts and the ice begins melting, pressure lets up, and eruptions surge. They belch CO2 that produces more warming, which melts more ice, which creates a self-feeding effect that tips the planet suddenly into a warm period. A 2009 paper from Harvard University says that land volcanoes worldwide indeed surged six to eight times over background levels during the most recent deglaciation, 12,000 to 7,000 years ago. The corollary would be that undersea volcanoes do the opposite: as earth cools, sea levels may drop 100 meters, because so much water gets locked into ice. This relieves pressure on submarine volcanoes, and they erupt more. At some point, could the increased CO2 from undersea eruptions start the warming that melts the ice covering volcanoes on land?
That has been a mystery, partly because undersea eruptions are almost impossible to observe. However, Tolstoy and other researchers recently have been able to closely monitor 10 submarine eruption sites using sensitive new seismic instruments. They have also produced new high-resolution maps showing outlines of past lava flows. Tolstoy analyzed some 25 years of seismic data from ridges in the Pacific, Atlantic and Arctic oceans, plus maps showing past activity in the south Pacific.
The long-term eruption data, spread over more than 700,000 years, showed that during the coldest times, when sea levels are low, undersea volcanism surges, producing visible bands of hills. When things warm up and sea levels rise to levels similar to the present, lava erupts more slowly, creating bands of lower topography. Tolstoy attributes this not only to the varying sea level, but to closely related changes in earth’s orbit. When the orbit is more elliptical, Earth gets squeezed and unsqueezed by the sun’s gravitational pull at a rapidly varying rate as it spins daily—a process that she thinks tends to massage undersea magma upward, and help open the tectonic cracks that let it out. When the orbit is fairly (though not completely) circular, as it is now, the squeezing/unsqueezing effect is minimized, and there are fewer eruptions.
The idea that remote gravitational forces influence volcanism is mirrored by the short-term data, says Tolstoy. She says the seismic data suggest that today, undersea volcanoes pulse to life mainly during periods that come every two weeks. That is the schedule upon which combined gravity from the moon and sun cause ocean tides to reach their lowest points, thus subtly relieving pressure on volcanoes below. Seismic signals interpreted as eruptions followed fortnightly low tides at eight out of nine study sites. Furthermore, Tolstoy found that all known modern eruptions occur from January through June. January is the month when Earth is closest to the sun, July when it is farthest—a period similar to the squeezing/unsqueezing effect Tolstoy sees in longer-term cycles. “If you look at the present-day eruptions, volcanoes respond even to much smaller forces than the ones that might drive climate,” she said.
Daniel Fornari, a senior scientist at Woods Hole Oceanographic Institution not involved in the research, called the study “a very important contribution.” He said it was unclear whether the contemporary seismic measurements signal actual lava flows or just seafloor rumbles and cracking. But, he said, the study “clearly could have important implications for better quantifying and characterizing our assessment of climate variations over decadal to tens to hundreds of thousands of years cycles.”
Edward Baker, a senior ocean scientist at the National Oceanic and Atmospheric Administration, said, “The most interesting takeaway from this paper is that it provides further evidence that the solid Earth, and the air and water all operate as a single system.”
A team of scientists and undergraduate students have analyzed the body size for 25 marine species, including whales, sharks, squids, and other ocean giants. The project elucidates both the challenges of arriving at exact measurements and the human bias toward larger individuals.
“Several years ago I noticed that people kept staying that giant squids reached 60 feet in length, which is amazingly long,” says Craig McClain, the assistant director of the National Evolutionary Synthesis Center in Durham, N.C., and the primary author of the paper. “When I started actually looking at the data, I found that that estimate was actually quite unrealistic.”
McClain explained that the muscle fibers in squids loosen and stretch during decomposition, which could account for the measurement of specimens found ashore in the 1800s. This new research indicates that the longest scientifically verified length is estimated at 12 meters (nearly 40 feet).
“It’s one part a databasing effort and one part historical research: double-checking museum specimens; talking with other scientists and collectors; and even checking eBay for specimens for sale,” McClain says.
To cast a wider net, he invited graduate and undergraduate students to join the project and select the marine species that most fascinated them. The results of their collective research will be published Tuesday, January 13 to PeerJ.
The species range from well-known behemoths like the Great White Shark, Giant Octopus, and walrus to more obscure creatures such as the Giant Tubes Worm and the Colossal Squid.
Meghan Balk, a coauthor and Ph.D. candidate at the University of New Mexico, researched the Southern Elephant Seal, as well as several shark species. For her, the study illustrated the great variability of size within a single species.
“What people think of as the biggest representatives aren’t usually the most optimal,” Balk says. “It says a lot about what it means to be large. How beneficial is it to be the biggest in a big species?”
Bigger isn’t always better. The tallest man in recorded history, Robert Wadlow, stood at 2.72 meters (nearly 9 feet), which is far from the average human height. Individuals like Wadlow often had shortened lifespans because of health complications related to their size.
Marine megafauna can also fall into a wide range of sizes within the same species.
“It’s fascinating as to why there is size variation [and] why everything isn’t less skewed,” Balk says. “How many sizes does an organism go through from the time it’s born to the time it’s an adult?” She explains that while mammals eat the same diet throughout their lives, animals like fish, sharks, and turtles eat different foods as they grow. For these species, size has a cascading effect within marine food webs.
The authors also considered environmental factors that could give rise to bigger species, as well as situations in which a larger size would be beneficial. For example, the Giant Clam can reach lengths of 1.37 meters (4.5 feet) because it receives additional nourishment from symbiotic photosynthetic bacteria. Similarly, larger Whale Sharks and Blue Whales are less susceptible to starvation: If a habitat is depleted of food, these filter-feeders have the mass to support a migration and subsequent fasting to reach more plankton-rich waters.
“Metabolism is a function of size because it indicates how much oxygen and carbon an animal consumes,” McClain says. “Knowing whether a whale shark is 10 tons, 15 tons, or 20 tons lets us know how many light bulbs worth of energy it uses every day.”
In tackling a search that would become quite gigantic itself, the authors contacted fisheries, marine centers, and other scientists.
“This is one of my first experiences in doing research in such a collaborative setting,” says Catherine Chen, a coauthor and Duke University junior who investigated the Blue Whale, Sperm Whale, and Ocean Sunfish. “I got to work with the International Whaling Commission’s datasets, which allowed me to look and play with over 200 years of whale capture data.”
Social media also proved advantageous to the project. McClain created a website, The Story of Size, where the authors posted regularly. The students promoted their work by sharing updates and their own impressions. With posts like, “Why You Should Give a Damn about a Giant Clam,” the site added a playful tone to the scientific discourse and also made the project more accessible to the general public.
“Having them write everything as a report is probably a disservice. Those are different styles of writing that require different techniques,” McClain says. “The big question is: Can you do research and outreach at the same time and not have it become a burden?”
The students were also required to tweet about their research, which for some, including Chen, meant creating their first Twitter accounts.
“Twitter’s really good for reaching out to the general public but also for talk between scientists,” Chen says. Through Twitter she met Trevor Branch, a professor of aquatic and fishery science at the University of Washington. Branch was able to help Chen with data on Blue Whales and even became a coauthor of the paper.
While academics including Branch and institutions like the IWC welcomed the opportunity to share their data, some sources were reluctant. The team hopes their work will help shift the attitude toward open access in a more favorable direction.
“A lot of questions that we sought to answer are still not answered either because of lack of research or lack of access,” Balk says. “I think that this paper will open up discussions about collecting and sharing data to gain a broader understanding of a species.”
Despite challenges, McClain is pleased with his team’s results, which he thinks will slowly replace the erroneous measurements found in academic papers, fishery databases, textbooks, and more.
“Precise, accurate, and quantified measurements matter at both a philosophical and pragmatic level,” McClain says. “Saying something is approximately ‘this big,’ while holding your arms out won’t cut it, nor will inflating how large some of these animals are.”
Mysteries of the deep come alive as satellite data bring thousands of uncharted sea mountains and new clues about deep ocean structures into focus
Accessing two previously untapped streams of satellite data, scientists at Scripps Institution of Oceanography at UC San Diego and their colleagues have created a new map of the world’s seafloor, creating a much more vivid picture of the structures that make up the deepest, least-explored parts of the ocean. Thousands of previously uncharted mountains rising from the seafloor and new clues about the formation of the continents have emerged through the new map, which is twice as accurate as the previous version produced nearly 20 years ago.
Developed using a scientific model that captures gravity measurements of the ocean seafloor, the new map extracts data from the European Space Agency’s (ESA) CryoSat-2 satellite, which primarily captures polar ice data but also operates continuously over the oceans, and Jason-1, NASA’s satellite that was redirected to map the gravity field during the last year of its 12-year mission.
Combined with existing data and drastically improved remote sensing instruments, the new map, described in the journal Science, has revealed details of thousands of undersea mountains, or seamounts, extending a kilometer or more from the ocean bottom. The new map also gives geophysicists new tools to investigate ocean spreading centers and little-studied remote ocean basins.
“The kinds of things you can see very clearly now are abyssal hills, which are the most common land form on the planet,” said David Sandwell, lead scientist of the paper and a geophysics professor in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics (IGPP) at Scripps.
The authors of the study say the map provides a new window into the tectonics of the deep oceans. Previously unseen features in the map include newly exposed continental connections across South America and Africa, and new evidence for seafloor spreading ridges at the Gulf of Mexico that were active 150 million years ago and are now buried by mile-thick layers of sediment.
“One of the most important uses of this new marine gravity field will be to improve the estimates of seafloor depth in the 80 percent of the oceans that remains uncharted or is buried beneath thick sediment,” the authors say in the report.
“Although CryoSat-2’s primary mission is in the cryosphere, we knew as soon as we selected its orbit that it would be invaluable for marine geodesy, and this work proves the point,” said Richard Francis, a coauthor of the paper and project manager for the development of CryoSat-2 at the European Space Agency, and honorary professor in the Department of Earth Sciences at University College London.
The new map also provides the foundation for the upcoming new version of Google’s ocean maps to fill large voids between shipboard depth profiles.
“The team has developed and proved a powerful new tool for high-resolution exploration of regional seafloor structure and geophysical processes,” says Don Rice, program director in the National Science Foundation’s (NSF) Division of Ocean Sciences. “This capability will allow us to revisit unsolved questions and to pinpoint where to focus future exploratory work.”
“The use of satellite altimeter data and Sandwell’s improved data processing technique provides improved estimates of marine gravity and bathymetry world-wide, including in remote areas,” said Joan Cleveland, Office of Naval Research (ONR) deputy director, Ocean Sensing and Systems Division. “Accurate bathymetry and identifying the location of seamounts are important to safe navigation for the U.S. Navy.”
In addition to Sandwell and Francis, coauthors of the paper include R. Dietmar Muller of the University of Sydney, Walter Smith of the NOAA Laboratory for Satellite Altimetry, and Emmanuel Garcia of Scripps.
The study was supported by NSF, ONR, the National Geospatial-Intelligence Agency, and ConocoPhillips.