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Geophagus sp. “Rio Turiacu”
- From: Rio Turiacu, Brazil
- Size: 6 inches (15 cm)
Geophagus spec. “Rio Turiacu,” a “big eye” Geophagus from far eastern Brazil, is smaller than other Geophagus in the G. surinamensis group. With the relocation of Brazil’s tropical fish export hub from Manaus to Belem, more species from the region around the mouth of the Amazon are becoming available. Among these include this peaceful, smaller Geophagus that will do well in a 65-gallon (246-liter) tank with larger characins and loricariids.
For more check out our Import Report from our SEP/OCT 2015 Issue!
Posted September 15th, 2015. Add a comment
An Abyssal Grenadier smiles for the camera at 4800 meters depth in the Porcupine Abyssal Plain. (Image: WHOI/NSF)
The deep sea is a mysterious world of darkness, an inky black expanse of water descending thousands of meters into geological fissures. But recently, several research expeditions have forayed into the trenches, providing a view – spatially and temporally limited as it may be – into the least known habitats on Earth.
Alan Jamieson, a Senior Lecturer at the University of Aberdeen, has been involved in many of these efforts, using baited camera landers to examine some of the oceans’ 38 distinct habitats that extend below 6000 meters depth. He compares these deep-sea canyons to inverted mountains – isolated zones where unique organisms may develop far from the genetic influence of incoming individuals. Jamieson and other researchers want to see just how distinct each habitat is, but given the remoteness, depth, and sizes of the sites, it’s not so easy to have a look around and catalog different species.
At the Deep Sea Biology Symposium in Aveiro, Portugal last week, Jamieson provided a guided tour of the trenches. The tools of the trade are typically autonomous, camera-outfitted platforms that work something like this: a dead fish is strapped to a metal scaffold and sent to the bottom of a trench. As fish, eels, shrimp, and other alien species come in for the free buffet, the lights go up and cameras capture the scene. With time, the next level of predators come in, drawn by the unusually high density of prey; if you’re lucky, multiple trophic levels can show up in the same frame.
Over the course of several years, Jamieson and the consortium of scientists comprising the HADES team have conducted 188 lander deployments at several different sites across multiple ocean basins. This geographically dispersed effort has given Jamieson an appreciation for the entire hadal system, setting him apart in some ways from the superlative seekers who target the bottom of the Mariana Trench because it’s the ocean’s deepest point. “How much would you learn about mountain ecology,” he asks by way of analogy, “if you only studied the top of Mt. Everest? It’s bizarre that we still do this, this obsession with the deepest point.”
For example, when comparing species from the Mariana and Kermadec Trenches in the South Pacific with those from the Puerto Rico Trench, some of the same amphipods (think slightly squishy crustaceans) were found at all three sites. This is remarkable – these creatures are finely attuned to the deep-sea habitat, and yet they seem able to hop thousands of kilometers between watering holes, as it were. Whether this happens by riding natural ocean currents or is dependent upon global ship traffic is currently unknown.
Late last year, the team released a highlight reel of trench biology, above. There are balletic shrimp, cartoonishly proportioned eels, and the deepest fish yet observed, a snailfish cruising by at 8,145 meters depth. The conspicuous lack of bony fish below the ~8000 meter mark is something the HADES team is investigating further. Is it a random number that will be disproven with more observations, or is this a meaningful boundary, possibly an evolutionary remnant of a past epoch when the oceans maxed out at that depth? “The more we look at it,” says Jamieson, “the more it looks like there’s something to it.”
The deepest parts of the oceans also provide a distressing reminder of the globalized reach of anthropogenic influences. PCB plasticizers were found in the Mariana and Kermadec Trenches, and concentrations of the flame retardant PBDE in amphipods were surprisingly high. “These areas are every bit as polluted as if we would look 50 meters off the coast,” Jamieson reports, “which is quite sad.”
The ocean’s depths may not be entirely pristine any more, but they remain alluringly mysterious. “Every time you land on the bottom,” Jamieson says, “it’s like landing on another planet.”
Author: Jeffrey Marlow
Originally published here: http://blogs.discovermagazine.com/the-extremo-files/2015/09/11/have-scientists-found-the-worlds-deepest-fish/
Posted September 14th, 2015. Add a comment
This is an artist’s rendering of Pentecopterus.
You don’t name a sea creature after an ancient Greek warship unless it’s built like a predator.
That’s certainly true of the recently discovered Pentecopterus, a giant sea scorpion with the sleek features of a penteconter, one of the first Greek galley ships. A Yale University research team says Pentecopterus lived 467 million years ago and could grow to nearly six feet, with a long head shield, a narrow body, and large, grasping limbs for trapping prey. It is the oldest described eurypterid — a group of aquatic arthropods that are ancestors of modern spiders, lobsters, and ticks.
A detailed description of the animal appears in the Sept. 1 online edition of the journal BMC Evolutionary Biology.
“This shows that eurypterids evolved some 10 million years earlier than we thought, and the relationship of the new animal to other eurypterids shows that they must have been very diverse during this early time of their evolution, even though they are very rare in the fossil record,” said James Lamsdell, a postdoctoral associate at Yale University and lead author of the study.
“Pentecopterus is large and predatory, and eurypterids must have been important predators in these early Palaeozoic ecosystems,” Lamsdell said.
Geologists with the Iowa Geological Survey at the University of Iowa discovered the fossil bed in a meteorite crater by the Upper Iowa River in northeastern Iowa. Fossils were then unearthed and collected by temporarily damming the river in 2010. Researchers from Yale and the University of Iowa have led the analysis.
The fossil-rich site yielded both adult and juvenile Pentecopterus specimens, giving the researchers a wealth of data about the animal’s development. In addition, the researchers said, the specimens were exceptionally well preserved.
“The Winneshiek site is an extraordinary discovery,” said Yale paleontologist Derek Briggs, co-author of the study. “The fossils are preserved in fine deposits of sediments where the sea flooded a meteorite impact crater just over 5 km in diameter.” 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.
“What’s amazing is the Winneshiek fauna comprise many new taxa, including Pentecopterus, which lived in a shallow marine environment, likely in brakish water with low salinity that was inhospitable to typical marine taxa,” said Huaibao Liu of the Iowa Geological Survey and the University of Iowa, who led the fossil dig and is a co-author of the paper. “The undisturbed, oxygen-poor bottom waters within the meteorite crater led to the fossils’ remarkable preservation. So this discovery opens a new picture of the Ordovician community that is significantly different from normal marine faunas.”
The National Science Foundation supported the research. Additional co-authors of the study were Robert M. McKay and Brian Witzke of the Iowa Geological Survey and the University of Iowa.
Story Source: Yale University
Posted September 4th, 2015. Add a comment
It’s not the Loch Ness monster, but a Yellowknife angler has ignited debate of his own after landing, and then releasing, a fluorescent green pike while fishing in Great Slave Lake.
“The whole top of the fish had a different green,” said Randy Straker. “If you look at the mouth, it looked like green lipstick. It was so bright.”
Straker was fishing with his friend Craig Thomas on Sunday in the lake’s North Arm when he made the catch.
After pulling the pike into the boat — Straker estimated it at 38 to 40 inches and 12 to 14 pounds — the two men snapped a few photos and released their catch. Afterward, though, they realized that they’d caught something quite unique.
“In hindsight, after looking at the pictures, we should have taken a whole lot more,” he said. “But we compared some pictures that we’d taken previously of a fish. And when you put it up against another pike, its way lighter. The fins were kind of a translucent green as opposed to the darker colors of a regular pike.
Avid fishermen, Thomas and Straker had worked their way around the lake for the past five years, and had “just started … exploring in that area,” said Straker.
The two were finishing up their day when Straker landed the fish. Pike, also known as jackfish, are common in Great Slave Lake, but when the catch passed by the boat, both men realized something was different.
“I was wearing polarized lenses, and I thought maybe that was causing some different coloration in the fish,” he said. “I was just about to pull my glasses off to take another look… and then my buddy made a comment about how strange the fish looked.
“Reeled it in a little tighter, and then just as it got close to the boat it kind of flared its gills and its mouth came wide open. And you could see right down its throat, and it was very fluorescent green.”
‘Like nothing we’d ever seen’
Asked if he’d seen anything like the pike before, Straker’s response was emphatic: “Nothing even close.
“We’ve seen kind of the albino look, where you might get a 50/50 split, where half the fish is lacking pigment, or we’ve seen some irregular spots, but this fish was totally, head to tail, like nothing we’d ever seen.”
Story Source: Northwind, CBC News
Originally published here: http://www.cbc.ca/news/canada/north/neon-jackfish-leaves-yellowknife-fisherman-stumped-1.3204762
Researcher Cody Clements places bottle caps into the rocky sea floor off Votua Reef, on the Coral Coast of the Fiji Islands. The caps are used to anchor small colonies of coral for experimentation to understand how crown-of-thorns sea stars and seaweed affect coral growth. The bottle caps allow for the coral colonies to be removed for accurate weighing.
Credit: Cody Clements, Georgia Tech
On the coral reef, knowing who’s your friend and who’s your enemy can sometimes be a little complicated.
Take seaweed, for instance. Normally it’s the enemy of coral, secreting toxic chemicals, blocking the sunlight, and damaging coral with its rough surfaces. But when hordes of hungry crown-of-thorns sea stars invade the reef, everything changes, reports a study to be published August 25 in the journal Proceedings of the Royal Society B.
Seaweeds appear to protect coral from the marauding sea stars, giving new meaning to the proverb: “The enemy of my enemy is my friend.” The findings demonstrate the complexity of interactions between species in ecosystems, and provide information that could be useful for managing endangered coral reefs.
“On the reefs that we study, seaweeds reduce coral growth by both chemical and mechanical means,” said Mark Hay, a professor in the School of Biology at the Georgia Institute of Technology and the paper’s senior author. “But we found that seaweeds can benefit corals by reducing predation by the crown-of-thorns sea stars. Corals surrounded by seaweeds were virtually immune to attack by the sea stars, essentially converting the seaweeds from enemies to friends.”
The research was supported by the National Science Foundation, the National Institutes of Health and the Teasley endowment at Georgia Tech.
Crown-of-thorns sea stars (Acanthaster planci) are a major problem in the Pacific, where populations of the organisms rise and fall in cycles. On the Great Barrier Reef, for example, coral cover has declined by more than 50 percent over 25 years, and the voracious spine-covered creatures – which can travel as much as 80 meters per day – get much of the blame.
“You don’t have to see the crown-of-thorns to know they have been on the reef,” said Cody Clements, a Georgia Tech graduate student in Hay’s lab and paper’s first author. “You can see where they have been because they leave trails of bleached white coral. All they leave behind are the coral skeletons.”
The sea stars climb onto favored corals, invert their stomachs out through their mouths, and digest away the corals’ living tissues – leaving white skeletons like a trail of bread crumbs that allowed Clements to not only see where the creatures had been, but also to track them to hiding places in the rocks.
During a two-year study in a marine protected area off the coast of the Fiji Islands, Clements used both observations and field experiments to examine the role of sea stars and seaweeds in the health of coral.
“Marine protected areas where we work are often surrounded by areas of coral reef that are degraded and have lots of seaweeds,” said Clements. “If seaweed is increasing in prevalence in these degraded areas, it’s likely that these predators will move into protected areas with more coral and less seaweed. That could compromise conservation efforts in these relatively small marine protected areas established to protect coral.”
Clements first assessed the impact of seaweeds by comparing the growth of corals surrounded by varying levels of seaweed cover. To accurately measure growth, he established test colonies of the coral Montipora hispida attached to the necks of plastic soft drink bottles. Matching bottle caps were nailed into seabed rock, allowing colonies to be unscrewed from their anchorages to be accurately weighed, then returned. He placed varying amounts of the seaweed Sargassum polycystum adjacent to each test colony.
“The seaweed had a negative effect on the growth of the coral, and the more seaweed that was present, the greater the impact I observed,” he said.
To study the relationship between sea star attacks and seaweed cover, Clements used photographs to assess the amount of sea star damage to different coral colonies outside the marine protected area, and related the damage to the amount of seaweed on corals in the attacked areas. Coral colonies that had been attacked had, on average, just eight percent seaweed coverage, while nearby colonies of the same species that had not been attacked averaged 55 percent coverage of seaweeds.
To more directly assess the protective role of the seaweed, Clements conducted an experiment. He fabricated ten cages in which he placed two Montipora coral colonies, one surrounded by varying levels of seaweed – between two and eight fronds – and the other lacking adjacent seaweeds. Into each cage he placed a sea star, then observed how much of each coral would be eaten.
“At the highest densities of seaweed, the sea stars were completely deterred,” Clements said. “They wouldn’t eat the coral surrounded by the seaweeds.” Coral surrounded by lower densities of seaweed were sometimes eaten, while the corals without seaweed protection were always consumed by the sea stars.
Researchers aren’t sure if the protective effects of the seaweed are mechanical or chemical – or perhaps both. But when Clements repeated the experiment with plastic aquarium seaweed instead of real seaweed, he found that it also had protective effects, suggesting the seaweed may be simply physical impediments making the coral difficult for the sea stars to find or consume.
Finally, Clements examined sea star feeding when the predator was given a choice between an unprotected coral it doesn’t normally consume (Porites cylindra) and Montipora – a favored prey – that had been surrounded by Sargussum. The sea stars didn’t eat the Montipora, and would wait as long as ten days before finally consuming the Porites.
“If you’ve got a choice between ice cream and broccoli, you’re going to choose ice cream – unless broccoli is the only thing you can get,” he said.
The varying relationship between coral and seaweed illustrates the kind of complexity scientists have to understand when studying species-diverse ecosystems such as coral reefs, Clements noted.
“In a scenario that didn’t involve the crown-of-thorns sea stars, interactions with the seaweed would have been negative for the coral,” he noted. “But when you add the crown-of-thorns into the equation, it can be beneficial for the coral to be associated with the seaweed. Even if it suffers reduced growth, that’s better than being eaten.”
Information from research like this can help scientists protect corals, which are essential to the survival of reef ecosystems.
“We are interested not only in how direct interactions between species play out, but also how these indirect interactions come into the picture and influence the wider community,” said Clements. “When it comes to coral reefs, that is very important because these interactions can affect the trajectory of an entire community of organisms.”
Story Source: Georgia Institute of Technology
Originally published here: www.sciencedaily.com/releases/2015/08/150825205850.htm
The larger Pacific striped octopus has a unique hunting style.
Photo credit: Roy Caldwell/UC Berkeley
Unlike most octopuses, which tackle their prey with all eight arms, a rediscovered tropical octopus subtly taps its prey on the shoulder and startles it into its arms.
“I’ve never seen anything like it,” said marine biologist Roy Caldwell, a University of California, Berkeley, professor of integrative biology. “Octopuses typically pounce on their prey or poke around in holes until they find something. When this octopus sees a shrimp at a distance, it compresses itself and creeps up, extends an arm up and over the shrimp, touches it on the far side and either catches it or scares it into its other arms.”
The creature, known as the larger Pacific striped octopus, also turns out to be among the most gregarious of known octopuses. While most species are solitary, these have been seen in groups of up to 40 off the Pacific coasts of Nicaragua and Panama.
And while male octopuses typically share sperm with females at arm’s length, ready to flee should the female get aggressive or hungry, mating pairs of this octopus when observed in captivity sometimes cohabit in the same cavity for at least a few days while mating, with little indication of escalated aggression. Mating pairs have even been observed to share meals in an unusual beak-to-beak position.
They do engage in rough sex, however. The pair grasp each other’s arms sucker-to-sucker and mate beak-to-beak, as if kissing. The females mate frequently and lay eggs over several months, whereas the females of most known octopuses die after a single brood.
Little known about world’s octopuses
The peculiar behaviors seen in the larger Pacific striped octopus are actually a testament to how little is known about most octopuses, Caldwell said. While their behavior and neurobiology have been extensively studied, most research is based on observations of just a handful of the more than 300 species of octopus worldwide.
“There are a lot of species of octopus, and most have never even been seen alive in the wild and certainly haven’t been studied,” he said.
Caldwell and his colleagues, including Richard Ross of the California Academy of Sciences and former UC Berkeley doctoral student Christine Huffard of the Monterey Bay Aquarium Research Institute, will publish their findings Aug. 12 in the journal PLOS ONE.
A fourth co-author, Panamanian biologist Arcadio Rodaniche, observed much of this strange behavior in the 1970s while studying captured specimens in a saltwater swimming pool in Panama. The behavior was so at odds with accepted octopus behavior, however, that he was unable to publish more than an abstract. The species has still not been officially described and has no scientific name.
Caldwell, too, once doubted the brief description of the octopus’s behavior, and only stumbled across the species while pursuing a smaller relative, Octopus chierchiae, on the Pacific coast of Central America. Both are “harlequin” octopuses, so called because of their semi-permanent stripes and spots. The animal lives in water between 40 and 50 meters (150 feet) deep, typically on muddy, sandy plains at the mouths of rivers, probably living in cast-off shells or rock cavities. Females grow to less than 7 centimeters across (3 inches), while males max out at less than 4.5 centimeters (2 inches).
Ross and Caldwell obtained 24 live specimens from a pet supplier between 2012 and 2014 and observed them in their laboratories at the California Academy and UC Berkeley. Ross even put some on display at the academy’s Steinhart Aquarium, where guests could have observed several pairs mating daily and producing multiple clutches of eggs.
“Personally observing and recording the incredibly unique cohabitation, hunting and mating behaviors of this fascinating octopus was beyond exciting — almost like watching cryptozoology turn into real-life zoology,” Ross said. “It reminds us how much we still have to learn about the mysterious world of cephalopods.”
“Each time a different type of octopus is studied, we need to redefine our theories about their behavior. It turns out most don’t live up to their ‘denizen of the deep’ reputation,” Huffard said.
Hundreds of young octopuses
In these captive environments, the biologists observed females laying eggs for up to six months and brooding for up to eight months. Even after their eggs began hatching, females continued to feed, mate and lay hundreds more eggs — another unusual behavior.
The larger Pacific striped octopus exhibits a striking high-contrast display of colors and patterns, which can vary from a pale to dark reddish-brown hue to black with white stripes, and spots with both smooth and uneven skin textures.
“They certainly respond to one another when they display their highly contrasting stripes and spots, so their coloration appears to be useful for group living,” Caldwell said. “Nevertheless, while they tolerate one another and sometimes pair up, I don’t think they are highly social.
“Only by observing the context in which these behaviors occur in the wild can we begin to piece together how this octopus has evolved behaviors so radically different from what occurs in most other species of octopus,” he added.
Story Source: University of California – Berkeley
Originally published here: www.sciencedaily.com/releases/2015/08/150812151220.htm
This is an adult coral (Pocillopora damicornis)
Photo Credit: Hollie Putnam
A new study from scientists at the University of Hawai’i — Mānoa’s (UHM) Hawai’i Institute of Marine Biology (HIMB) reveals that preconditioning adult corals to increased temperature and ocean acidification resulted in offspring that may be better able to handle those future environmental stressors. This rapid trans-generational acclimatization may be able to “buy time” for corals in the race against climate change.
Hollie Putnam, lead author of the Journal of Experimental Biology-featured study and HIMB assistant researcher; and Ruth Gates, co-author and HIMB senior researcher, exposed two groups of parental corals to either ambient ocean conditions or IPCC-predicted future ocean conditions — warmer and more acidic water. As expected, the harsher future conditions negatively affected the health of the parental coral — lowering photosynthesis and production to consumption ratios. Surprisingly, however, the offspring of parents who were exposed to future conditions appeared healthier when re-exposed to the harsher environment.
“By preconditioning the corals while the offspring are being brooded it may be possible to increase the offspring’s potential to perform under stressful environmental conditions,” said Putnam.
Corals have been suffering huge losses in diversity and abundance on reefs worldwide due to local stressors such as overfishing, coastal development, pollution, and sedimentation, for example. Further, global stressors such as increased temperature result in coral bleaching — a breakdown in the symbiosis between the cnidarian host and the symbiotic algae — which can cause mass coral mortality. Additionally, corals exposed to ocean acidification can struggle to build their skeletons and reefs are undergoing bio erosion and dissolution.
“Together these local and global stressors are placing an unprecedented strain on coral reef ecosystems. It has even been predicted that some corals may go extinct and the reefs will not provide the same biological diversity and provisioning — goods and services valued at hundreds of billions of dollars annually,” said Putnam.
It is thought genetic adaption is the primary option for corals to respond to climate change. With the rapid rate of environmental change, however, genetic adaptation may not be able to keep pace. Putnam and Gates were interested in the potential for other more rapid response mechanisms like the acclimatization provided when adults provision their offspring based on their environmental experience. The researchers think epigenetics, or a change in the quantity and product of a gene without a change in DNA sequence, may be one such acclamatory mechanism that allows the organism to rapidly adjust to environmental change. Epigenetics and parental effects, they say, may help to buffer corals against the rapidly changing climate.
“Our work suggests that when we consider multiple life stages in connection and their environmental history, corals have resources to respond to climate change that we have not yet considered fully,” said Putnam. “This may be good news for corals of the future.”
In a new series of experiments, the researchers are expanding their analysis to more coral life stages by tracking the coral larvae from preconditioning in their parents until they settle and grow into juveniles. Their goal is to assess the “grandchildren” after 3-4 years, when the first offspring become reproductive. They are also comparing the response to temperature and ocean acidification simultaneously and separately to determine if one factor is more influential than another.
Story Source: University of Hawaii at Manoa
Originally published here: <www.sciencedaily.com/releases/2015/08/150805191724.htm>.
By Ted Judy
The author’s wild-caught oscars imported from the Rio Orinoco. Photograph by Ted Judy.
Nine months ago, I decided to get a group of oscars to grow out, which was when I found out that there are not very many in stores, so I ended up buying some wild fish imported from the Orinoco River in Venezuela. They are probably Astronotus ocellatus, but they may also be an undescribed species. They have a lace-like pattern in their fins that is not seen in the tank strain A. ocellatus, and they do not have as much red (which has been developed in tank strains through selective breeding). I have six of them growing up in a 75-gallon tank. I expect to have to reduce the number eventually, and I am hoping to end up with a nice breeding pair. So far the fish are much more shy than the tank-raised oscars I have kept in the past, but they are no less intelligent. I can tell by the way they look at me. Check out this video of the author’s oscars as they go through their morning routine, and another of them a year later.
One of the cichlid fish from Guatemala, Thorichthys meeki, collected by LSU Curator of Ichthyology Prosanta Chakrabarty for the study that refuted the date in which the Isthmus of Panama was formed.
Credit: Courtesy of Prosanta Chakrabarty, LSU
New study shakes up understanding of when continents connected
A long-standing fact widely accepted among the scientific community has been recently refuted, which now has major implications on our understanding of how Earth has evolved.
Until recently, most geologists had determined the land connecting North and South America, the Isthmus of Panama, had formed 3.5 million years ago.
But new data shows that this geological event, which dramatically changed the world, occurred much earlier. In a comprehensive biological study, researchers have confirmed this new information by showing that plants and animals had been migrating between the continents nearly 30 million years earlier.
“This means the best-dated geological event we ever had is wrong,” said Prosanta Chakrabarty, LSU Associate Professor in the Department of Biological Sciences and Curator of Ichthyology at the LSU Museum of Natural Science. His research on the evolution of freshwater and marine organisms in Central America was part of the study with colleagues at the Smithsonian Tropical Research Institute, American Museum of Natural History and University of Gothenburg, which included living and extinct mammals, birds, plants, fish and invertebrate animals published by the Proceedings of the National Academy of Sciences.
The researchers found large pulses of movement among these plants and animals between North and South America from 41 million, 23 million and eight million years ago. These coordinated spikes in migration imply that geological changes in Central America, such as landmass formation and new freshwater corridors, were aiding migration for many kinds of plants and animals.
“Before, South America was thought of as an island with no communication until 3.5 million years, so the only way to explain such high biodiversity was to say that it accumulated extremely fast. Now, with a longer history, we know that processes and patterns took a lot of time to form,” said Christine Bacon, lead author of the study and associate researcher at the University of Gothenburg. “Our results change our understanding of the biodiversity and climate, both at the regional and global levels.”
Even after the reported geological closure, geminate marine species, those close relatives found on opposite sides of the narrow isthmus, also provide evidence that this landmass between North and South America is more like a sponge where organisms can periodically pass rather than a solid barrier. The current expansion of the Panama Canal has yielded new fossils that have informed these observations.
“Now we know that the closure of the Isthmus of Panama, which is supposed to be one of the biggest deals in geology, is just one part of a really complicated puzzle of how the continents came together,” Chakrabarty said.
He and colleagues at LSU mapped the evolution of two major families of fishes in Central America — cichlids, which include many aquarium fish, and poeciliids, which include guppies and swordtails. They collected samples of fishes from every country in Central America and sequenced the DNA to determine the genetic relationship between species. Matching the skeletal structure of fish found in the fossil record, they calibrated the DNA-based evolutionary tree and determined the age of each species.
Because freshwater fish can only migrate when a new passage way opens to a river or lake, there must have been dry land with freshwater running through it, Chakrabarty said. Therefore, their arrival in Central America signifies early geological changes.
“The cool thing is there are so many freshwater fish species that are essentially stuck in one place until the land changes, so they can tell us about the history of the Earth,” he said.
The formation of the Isthmus of Panama had large-scale effects on the planet. It divided the Atlantic and Pacific oceans, thus changing sea levels and ocean currents. This affected global temperatures possibly causing periods of glaciation.
“The geology of this whole region is so complicated, and it’s amazing to me that the biology can inform us of that,” he said. Chakrabarty has been conducting research on Central American freshwater fish for about 15 years. He has received more than $1 million in National Science Foundation funding for this work. He and his lab have collected fish species from every country in Central America and have expanded the specimen collection at LSU to South America, the Greater Antilles and much of Asia. He is currently researching the evolution and migration of freshwater fish between South America, Central America and the Greater Antilles that may have began 50 to 60 million years ago.
Materials provided by Louisiana State University
Originally published here: www.sciencedaily.com/releases/2015/06/150609213351.htm
Rock crab habitats are predicted to shift away from warm temperatures at the equator and toward shallower, more oxygenated water.
Credit: J. MacCausland / U.S. Geological Survey
Modern mountain climbers typically carry tanks of oxygen to help them reach the summit. It’s the combination of physical exertion and lack of oxygen at high altitudes that creates one of the biggest challenges for mountaineers.
University of Washington researchers and collaborators have found that the same principle will apply to marine species under global warming. The warmer water temperatures will speed up the animals’ metabolic need for oxygen, as also happens during exercise, but the warmer water will hold less of the oxygen needed to fuel their bodies, similar to what happens at high altitudes.
The study, published June 5 in Science, finds that these changes will act together to push marine animals away from the equator. About two thirds of the respiratory stress due to climate change is caused by warmer temperatures, while the rest is because warmer water holds less dissolved gases.
“If your metabolism goes up, you need more food and you need more oxygen,” said lead author Curtis Deutsch, a UW associate professor of oceanography. “This means that aquatic animals could become oxygen-starved in the warmer future, even if oxygen doesn’t change. We know that oxygen levels in the ocean are going down now and will decrease more with climate warming.”
The study centered on four Atlantic Ocean species whose temperature and oxygen requirements are well known from lab tests: Atlantic cod that live in the open ocean; Atlantic rock crab that live in coastal waters; sharp snout seabream that live in the subtropical Atlantic and Mediterranean; and common eelpout, a bottom-dwelling fish that lives in shallow waters in high northern latitudes.
Deutsch used climate models to see how the projected temperature and oxygen levels by 2100 due to climate change would affect these four species’ ability to meet their future energy needs. If current emissions continue, the near-surface ocean is projected to warm by several degrees Celsius by the end of this century. Seawater at that temperature would hold 5-10 percent less oxygen than it does now.
Results show future rock crab habitat would be restricted to shallower water, hugging the more oxygenated surface. For all four species, the equator-ward part of the range would become uninhabitable because peak oxygen demand would become greater than the supply. Viable habitats would shift away from the equator, displacing from 14 percent to 26 percent of the current ranges.
The four animals were chosen because the effects of oxygen and temperature on their metabolism are well known, and because they live in diverse habitats. The authors believe the results are relevant for all marine species that rely on aquatic oxygen for an energy source.
“The Atlantic Ocean is relatively well oxygenated,” Deutsch said. “If there’s oxygen restriction in the Atlantic Ocean marine habitat, then it should be everywhere.”
Climate models predict that the northern Pacific Ocean’s relatively low oxygen levels will decline even further, making it the most vulnerable part of the ocean to habitat loss.
“For aquatic animals that are breathing water, warming temperatures create a real problem of limited oxygen supply versus elevated demand,” said co-author Raymond Huey, a UW professor of biology who has studied metabolism in land animals and in human mountain climbers.
“This simple metabolic index seems to correlate with the current distributions of marine organisms,” he said, “and that means that it gives you the power to predict how range limits are going to shift with warming.”
Previously, marine scientists thought about oxygen more in terms of extreme events that could cause regional die-offs of marine animals, also known as dead zones.
“We found that oxygen is also a day-to-day restriction on where species will live, outside of those extreme events,” Deutsch said. “Ranges will shift for other reasons, too, but I think the effect we’re describing will be part of the mix of what’s pushing species around in the future.”
Source: University of Washington
Originally published here: www.sciencedaily.com/releases/2015/06/150604162455.htm