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Neon jackfish leaves Yellowknife fisherman stumped

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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

Posted August 31st, 2015.

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Foes can become friends on the coral reef: How seaweed becomes coral’s friend when sea stars invade

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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

Posted August 27th, 2015.

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Octopus shows unique hunting, social and sexual behavior

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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

Posted August 13th, 2015.

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Parental experience may help coral offspring survive climate change

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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>.

Posted August 7th, 2015.

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Geological game changer: When continents connected

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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

Posted June 12th, 2015.

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Longest ever tiger shark tracking reveals remarkable, bird-like migrations

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This is the tiger shark from a side view.
Credit: Courtesy of Nick Filmalter/Danah Divers

Tiger sharks are among the largest and most recognizable sharks on the planet, yet many of their habits remain mysterious because they are long-distance travelers that are hard to track. But a new study, reported in the June 9 issue of the journal Scientific Reports, has yielded the first ever continuous, two or more-year satellite tagging tracks for the animals. This study reveals remarkable, and previously unknown, migration patterns more similar to birds, turtles and some marine mammals than other fishes.

Long believed to be mainly a coastal species, the tiger sharks, in fact, made more than 7,500 kilometer, round-trip journeys every year between two vastly different ecosystems — the coral reefs of the Caribbean and the open waters of the mid-North Atlantic. Furthermore, they returned reliably to the same overwintering areas each year, a discovery with significant conservation implications.

The study was led by James Lea and Brad Wetherbee, Ph.D., co-first authors, and senior author, Mahmood Shivji, Ph.D., all of whom work out of Nova Southeastern University’s (NSU) Guy Harvey Research Institute in Florida. Renowned marine artist and conservationist Guy Harvey, a Ph.D. fisheries ecologist, is also an author on the paper and co-led the project’s tagging work, which took place near Bermuda, in collaboration with the Bermuda Shark Project.

‘As apex predators, the presence of tiger sharks — and other large sharks — is vital to maintain the proper health and balance of our oceans,’ said Dr. Shivji, who is professor at NSU and also the director of NSU’s GHRI. ‘That’s why it’s so important to conserve them, and understanding their migratory behavior is essential to achieving this goal.’

Background

The details of the movements and migrations of tiger sharks and most other large shark species have been a mystery because they are difficult to track for more than a few months because of tag or other logistic limitations. For this project, the tags the team attached to sharks near Bermuda lasted in many cases more than two years, and in some cases more than three years, sending satellite position data each time an animal surfaced.

One tiger shark, named Harry Lindo, traveled more than 44,000 kilometers (27,000 miles), the longest track distance documented for a tiger shark and possibly the longest ever published for a shark.

‘It is truly remarkable,’ said Harvey of the animal’s travels.

Tiger Shark Highway

The researchers were able to show that adult male tiger sharks in the Atlantic repeatedly spend their winters in Caribbean island locales including the Bahamas, Turks and Caicos Islands, and Anguilla. Then, during summers, they travel far into the North Atlantic, often more than 3,500 kilometers and as far north as Connecticut, though well offshore in nearly the middle of the ocean.

‘These repeated journeys were very unexpected,’ said Lea, who also works out of the Marine Biological Association of the United Kingdom, ‘The tiger shark has traditionally been considered a coastal species, and it is rare among sharks to so easily and habitually switch between the two vastly different environments.’

Remarkably, the sharks followed the same pattern each year and returned to almost the same small area in the Caribbean each time.

‘Even though they’ve got a whole range of islands to choose from, it seems like each animal has its favorite winter spot,’ said Shivji.

For the tiger sharks, the migrations are something like a ‘highway road trip,’ on their way to definite destinations. Bermuda is a handy spot for tiger shark tagging because it is the equivalent of a popular highway exit — lots of animals stop off there for a break while heading north or south. But for the most part the animals travelled directly between their migration destinations, meandering around only after arriving.

Why They Go

What makes the tiger sharks so committed to particular areas is still an open question. At the south end, the story may be fairly simple. Female tiger sharks are common in the Caribbean in the winter, so the Caribbean may just be the best place for male tiger sharks to find dates, although this is just an educated guess.

Why they go so far north is more complicated. How far they go seems to be guided by avoidance of colder temperatures — information that offers one example of how migration research can help to predict the implications of climate change for sharks.

‘There’s got to be something really good up there to make the sharks undertake such massive, repeated swims, but exactly what is a puzzle,’ said Shivji.

One possibility is that they go to feed on young loggerhead turtles that also migrate north — indeed when the researchers examined stomachs of some tiger sharks killed by long liners in the region, they found turtle remains. But then there are also turtles much farther south.

Great White Similarities

The only other instance where researchers have found a broadly similar, repeated migration pattern between coastal and distant open water regions is with the warm-bodied, great white and salmon sharks in the Pacific Ocean. White sharks migrate in the winter from the California and Baja coasts to a mid-Pacific open water area dubbed the ‘White Shark Café.’

‘We joke that tiger sharks, not being media stars like white sharks, wouldn’t be comfortable in a ‘café’ and prefer to hang-out in their ‘truck-stop’ in the mid-Atlantic,’ says Wetherbee, who is also based at the University of Rhode Island.

Conservation Implications

Tiger sharks are nearing threatened status, in part because of targeting for the soup fin trade. One of the most important implications of the new research, therefore, is for conservation.

‘Understanding how these animals use the oceans is the first step toward effective conservation,’ said Harvey. ‘Protecting migratory species is a great challenge because they can be found in such a wide area. Protecting the areas where animals, such as tiger sharks, spend the most time is a tractable goal once those areas have been identified.’

Guided in part by early access to the GHRI team’s data about the importance of the Bahamas habitat to the tiger shark’s annual migratory pathways, The Bahamas government established a shark sanctuary in 2011 prohibiting commercial shark fishing in their territorial waters.

How to Follow Sharks

All of the satellite tracks for tiger sharks in this study, as well as ongoing tracks for other species including mako sharks, oceanic whitetip sharks and marlins, can be found online at http://www.ghritracking.org

Source: Nova Southeastern University

Originally published here: www.sciencedaily.com/releases/2015/06/150609213349.htm

Posted June 10th, 2015.

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Why some threatened corals swap ‘algae’ partners

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This image shows Caribbean star coral (Orbicella faveolata) with individual coral polyps showing different levels of bleaching during a warm summer bleaching event in summer 2014. Image taken off northern Florida Keys.
Credit: Rivah Winter

A new research study showed why threatened Caribbean star corals sometimes swap partners to help them recover from bleaching events. The findings are important to understand the fate of coral reefs as ocean waters warm due to climate change.

The University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science research team placed colonies of Caribbean star coral (Orbicella faveolata) in a heated tank for one to two weeks to replicate ocean conditions that would lead to both mild and severe coral “bleaching” — when corals turn white as a result of the loss of symbiotic algae living in their tissues. The corals, collected from waters off Miami, were then allowed to recover at two different water temperatures, below and above the local average, to see if they recovered with the same or different algal partners.

“Since ‘symbiont shuffling’ occurs in only some cases, we wanted to understand what drives this process and whether it could help corals adjust to climate change,” said Ross Cunning, a UM Rosenstiel School alumnus and lead author of the study. “We discovered that partner switching in Caribbean star corals is dependent upon the severity of the bleaching event and the temperature during recovery.”

The researchers discovered that severe bleaching and warmer water recovery temperatures caused corals to shuffle their symbionts in favor of more heat-tolerant algae, which belong to a group of symbionts called clade D, while mild bleaching and cooler recovery drove shifts toward the less heat-tolerant algae, in clade B. The study, published in the June 3 issue of the journal Proceedings of the Royal Society B, suggests that increases in heat-tolerant symbionts in the Caribbean star coral are greatest when bleaching is more severe and the recovery environment is warmer.

Corals depend on symbiotic algae to survive and build coral reefs. Increased ocean temperatures due to climate change can cause these symbiotic algae to be expelled from the coral, an event known as bleaching, which often leads to death. Climate change is one of the main threats to the Caribbean star coral (O. faveolata), which was were recently listed as a ‘threatened’ species under the U.S. Endangered Species Act.

“These findings help resolve a long-standing debate over why some corals switch partners after bleaching, while others do not,” said Andrew Baker, UM Rosenstiel School associate professor of marine biology and ecology and a Pew fellow in marine conservation. “They show that, as the oceans continue to warm and bleaching events become more severe, we might expect heat-tolerant symbionts to become a common feature of recovering reefs. Corals that can ‘buddy up’ with different algae might be more resistant to bleaching in the future.”

Two more recent studies, also conducted in Baker’s Coral Reef Futures lab at UM, showed how corals modify their symbionts in response to environmental changes. The first, published earlier this year in the journal Global Change Biology, showed how changes in symbiont partners following bleaching directly increased corals’ thermal tolerance. The second, published in the May issue of the journal Ecology, showed that, in addition to changing the types of algae they partner with, corals also fine-tune the number of algae they contain to deal with an ever-changing environment.

“Together, these studies suggest that that the rate of warming, timing between bleaching events, and severity of each bleaching event, will play an important role in determining coral survivorship,” said Baker. “We need to better understand these changes in order to accurately predict coral reef futures.”

Source: University of Miami Rosenstiel School of Marine & Atmospheric Science

Originally published here: www.sciencedaily.com/releases/2015/06/150604100915.htm

Posted June 8th, 2015.

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Sisters act together: Cichlid sisters swim together in order to reach the goal

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Cichlid fish in the Lake Tanganyika.

Credit: Stefanie Schwamberger

The manner and routes of dispersal vary with the species and the ecological conditions. Many fish form shoals to avoid predation. Shoaling with familiar conspecifics affords the fish an even greater advantage by increasing the benefit for relatives. This promotes the continuation and future spread of an individual’s own genetic information.

Franziska Lemmel-Schädelin, Wouter van Dongen, Yoshan Moodley and Richard Wagner from the Konrad Lorenz Institute of Ethology studied Neolamprologus caudopunctatus, a species of cichlid fish endemic to Lake Tanganyika, Africa’s second largest and the world’s second deepest freshwater lake. Lake Tanganyika has a surface volume of about 33,000 m², which corresponds to the size of Belgium. The researchers studied the influence of sex and size on dispersal and shoaling behavior.

Females dispersed longer distances than males

Lemmel-Schädelin and her field assistants carried out a number of dives in October and November 2008 to study the dispersal behavior and relationships of over 900 cichlids. The divers collected DNA samples from the dorsal fins and documented the body size and sex of the fish. An analysis of the data showed that over the course of their lives the females dispersed farther from their parental nesting sites than males.

“To avoid inbreeding and resource competition, it is usual among many animals for one sex to disperse farther from their place of birth than the other. Male-biased dispersal is more frequently the norm among mammals, with females remaining near the original nesting area. Among the cichlids we studied, on the other hand, it appears to be the females that disperse,” says ethologist Lemmel-Schädelin.

Kin-shoaling promotes the spread of an individual’s own genes

The researchers discovered another phenomenon while studying the familial relationships within the shoals. Small — and therefore probably younger — females tend to shoal with female siblings. Small males do not, instead preferring to shoal with non-sibling males. Larger — and therefore older — fish no longer exhibit this preference for kin-shoaling.

Richard Wagner explains this behaviour as follows: “Females disperse around eleven times as far from their parental nests than males. This naturally involves a certain risk for the females. We observed that females tended to shoal with their female siblings. They probably do so in order to minimize the risks of long-distance dispersal and to increase the chance of at least one member of the family making it.”

“Cichlid research is especially interesting from an evolutionary perspective,” says Lemmel-Schädelin. “Africa’s three largest lakes — Lake Victoria, Lake Tanganyika and Lake Malawi — are home to cichlids that are believed to have emerged from a limited source population. The ancestral animals followed the rivers to enter these lakes, where they found a number of ecological niches in which they began to develop in different directions. This makes it possible here to look at evolution in action, so to speak, and to research the emergence of new species and a rich repertoire of different behavior’s,” Lemmel-Schädelin explains.

Source: Veterinärmedizinische Universität Wien

Posted June 2nd, 2015.

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Genetic analysis of the American eel helps explain its decline

150528124204_1_540x360[1]
American Eels of the upper St. Lawrence grow slowly but attain larger sizes (top) compared with eels in coastal areas (bottom).
Credit: Guy Verreault/Current Biology 2015

The American eel has been a concern for the U.S. Fish and Wildlife Service since 2007, when it was first considered for, but failed to receive, Endangered Species Act protection. The numbers of these slender, slimy, ancient fish in freshwater areas have been decreasing rapidly due to dams, pollution, and overfishing, but scientists have been puzzled as to why the fish can’t recolonize. Now, a new look at eel genetics published on May 28 in Current Biology finds that there are differences between eels that feed in freshwater and eels that feed in brackish environments that were previously thought to be genetically interchangeable.

Both freshwater and brackish American eels are the same species, but they vary in size and have very different growth rates and life spans. Once a year, sexually mature eels from both groups migrate thousands of miles to spawn in the Sargasso Sea (located in the North Atlantic Ocean east of Bermuda). The offspring are carried off by the current to their new homes. It’s been thought that young American eels can detect whether they’ve ended up in brackish or freshwater habitats and acclimate accordingly. But this new study suggests that eels are predisposed to survive in these environments, depending on what genes they inherited.

“People have considered these differences in growth and age to be 100 percent due to phenotypic plasticity, independent of the genotype,” says lead author Scott Pavey, a postdoctoral fellow at the Integrated Biology Institute of Laval University in Quebec, Canada. “But what we found is that genes affect whether an eel can survive freshwater or brackish environments.” This helps explain why some conservation efforts to preserve the freshwater eel haven’t been successful, as more plentiful brackish eels cannot easily change their traits to survive in freshwater environments.

Pavey, in collaboration with ecologist Louis Bernatchez and colleagues, used new sequencing technologies to screen the eel genome in 45,000 places. The analysis identified 99 genes that differ between freshwater and brackish eels, including those associated with growth rate, heart development, and smell. It’s unknown whether this type of genetic differentiation exists in other, non-eel marine species with high levels of phenotypic plasticity.

The question remains, though, as to why eels would have such a strange approach to survival. The fish is considered evolutionarily ancient, so they must be doing something right. “It’s a different strategy, a kind of hedging your bets,” speculates Pavey. His team is now working to publish and release the entire genome of the eel. This will provide an important tool for other researchers to conduct similar studies on different aspects of eel ecology.

Source: Cell Press

Originally published here: www.sciencedaily.com/releases/2015/05/150528124204.htm

Posted May 29th, 2015.

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New Colonial Marine Organisms Discovered in Madeira

Favosipora purpura

Favosipora purpurea, one of the new species of bryozoans discovered on the island of Madeira.
Credit: Javier Souto et al.

The Portuguese island of Madeira is considered a diversity hotspot for bryozoans, which are colonial, principally marine, organisms. However, the fauna of these small animals only started being documented a short while ago. A team of Spanish and Portuguese scientists have now discovered two new species of bryozoans, as well as another that had previously only been found in the waters of Rio de Janeiro (Brazil).

To date, some 140 species of bryozoans have been identified in Madeira, which is why some authors consider the island to be a diversity hotspot for the zoological group. However, most of the knowledge they have of the region’s animals is from studies carried out by English researchers at the end of the 19th and beginning of the 20th centuries.

Over the last few years, the application of more modern study techniques, together with electron microscopy, has enabled the diversity of these organisms to be analysed in greater detail, meaning greater distinctions between species can be made. This technology, in the majority of cases, allows researchers to compare the material collected now with what was gathered previously.

Thanks to these new methods, scientists from various Spanish and Portuguese centres have analysed samples of rocks colonised by the organisms at a depth of 11 metres, which were collected from the south of the island in August 2013. The results, published in the journal Zootaxa, reveal the discovery of two new species: Favosipora purpurea and Rhynchozoon papuliferum.

“This study not only describes two species of bryozoans which are new to science, but six documented species from the island of Madeira and a species considered endemic to Brazil which was found outside those waters for the first time are also described again,” Javier Souto, a researcher affiliated with the University of Vienna and the department of Zoology and Biological Anthropology of the University of Santiago de Compostela (USC), said.

In order to draw these conclusions, the team studied material gathered by the researchers themselves and samples collected at the end of the 19th century held in the Manchester Museum (UK). “In doing this we were able to confirm that all this material corresponded to a species that had never been discovered before, which we named Rhynchozoon papuliferum,” said Souto.

According to the biologist, the name is related to the papilla-esque morphology of avicularians (zooids that are specialists in defence), “a fact that British scientist A. W. Waters (who gives his name to the collection of bryozoans in the English museum) had noticed as early as 1909, but the characteristic did not lead him to discover a new species,” explained the Spanish researcher.

However, Favosipora purpurea, which takes its name from the colour of its colonies, is the first species belonging to this genus to be observed in the Atlantic Ocean, and it had previously only been known to inhabit the Pacific and Indian Oceans. As for its characteristics, it is more or less circular with a two-centimetre diameter.

Rediscovering the bryozoans

“The bryozoans are one of the most important fouling organisms of the marine benthos and often go unnoticed because of their small size,” underlined the author. Around 6,000 species are currently known around the world, but the actual figure is believed to be in the region of 11,000.

These animals form colonies that range from a few millimetres to large colonies almost a metre in size and they can consist of a mere few zooids right up to thousands of them, with morphologies and functions within the group varying from one species to another.

“This morphological variation is what distinguishes one species from another. In order to observe this variation, a scanning electron microscope, which enables accurate identification, is required,” noted Souto. The study also enabled six previously recorded species to be re-observed on the Portuguese island, with the technology providing new data and images of said species.

The study was carried out within the framework of a species monitoring project whose objective is to recognise diversity and detect species introduced by human activity on the island of Madeira. The initiative was started in 2013 by Joao Canning Clode, a researcher at, among other centres, the Marine Biology Station of Funchal (Maderia).

Story Source: Plataforma SINC

Originally published here:  www.sciencedaily.com/releases/2015/05/150519083546.htm

Posted May 20th, 2015.

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