How brown trout tolerate heavily polluted water

New research from the University of Exeter and King’s College London has shown how a population of brown trout can survive in the contaminated waters of the River Hayle in Cornwall where metal concentrations are so high they would be lethal to fish from unpolluted sites.

The team believe this is due to changes in the expression of their genes. The research was funded by NERC and the Salmon and Trout Association.

The researchers compared the trout living in the River Hayle with a population living in a relatively clean site in the River Teign. The results showed that the accumulation of metals in the kidney and liver – where metals are stored and detoxified – were 19 and 34 times higher in the  Hayle trout, respectively. In the gill, concentrations averaging 63 times higher were present in the Hayle fish, but there were no differences in metal content in the gut. This accumulation of metals in the Hayle fish highlights their extraordinary tolerance of the extreme metal concentrations in their environment.

In order to investigate how the Hayle brown trout are able to tolerate such high levels of metal exposure, and also look for potential signs of toxicity, advanced high throughput sequencing was conducted at the Exeter Sequencing Facility to sequence the genes and then measure changes in their expression between the two river sites. The gene encoding a protein, metallothionein, responsible for binding, storing and detoxifying a number of metals, was found to be highly expressed in the River Hayle trout, indicating its importance in their ability to tolerate metals in their environment. Evidence of the presence of other metal-binding and transporting proteins, particularly those responsible for handling iron, was also found.

Usually metals cause toxicity in fish by causing oxidative damage and disrupting the balance of ions in the body. The team found evidence that to counter this toxicity, Hayle fish showed changes in genes responsible for maintaining the balance of these ions in the body and a modest increase in anti-oxidants.

This work was led by T. Uren Webster, Dr R. van Aerle and Dr E Santos from the University of Exeter and Dr N Bury from King’s College London, and has been published in the journal Environmental Science & Technology.

Tamsyn Uren Webster said: “The work demonstrates that this population of brown trout has developed strategies for dealing with the metal pollution in the water and accumulation in their tissues avoiding the lethal damage that such concentrations of metals would normally cause.”

A detailed understanding of how the Hayle trout population has developed this tolerance could have potential implications for re-stocking rivers and increasing food security in polluted regions of the world.

Dr Eduarda Santos from Biosciences said: “The story of the brown trout in the river Hayle is a fascinating one, demonstrating its resilience and its ability to defeat the odds and tolerate the challenges imposed upon them as a result of human activities. Many aspects of this story remain untold: we do not know how or when this tolerance has arisen, and, most importantly, we do not know what the future holds for them if they are challenged with further stressors in their environment. But we know that such populations need careful management; if the Hayle brown trout, with their unique physiology, were to be lost, it is possible that this river may never be home to brown trout again. Therefore, understanding the relationship of fish with their environment is a crucial requirement to effectively manage and protect our aquatic ecosystems.” 

Dr Nic Bury said: “Cornwall has a rich history of mining activity. Despite the cessation of the majority of this activity in the 19th and 20th centuries a number of rivers and estuaries, still possess elevated metals. Brown trout are extremely sensitive to metals when tested in the laboratory. However, biology is remarkable and adaptable, and it is astonishing that trout are able to survive and flourish in the river Hayle. It may be that this population is unique and an important component of the genetic diversity of brown trout.”

[Source Article]

ImageBrown trout   (Photo credit:


How Mussels Cling to Surfaces

By Denise Chow, Staff Writer
When mussels dangle from marine surfaces, they hold on by a cluster of fine threads. These filaments may appear flimsy, but they can actually withstand powerful impacts from currents or crashing waves. Now, researchers are unraveling the secret of these thin, bungeelike cords in order to develop more effective glues and other synthetic biomedical materials.

Unlike barnacles, which fasten themselves tightly to rocks or piers, mussels use silky fibers, called byssus threads, to loosely attach to a surface while still being able to drift and absorb nutrients in the water. So, how do these seemingly delicate threads help mussels stay put?

From laboratory tests and computer models, scientists at the Massachusetts Institute of Technology (MIT) discovered that roughly 80 percent of the length of byssus threads — the same parts of the threads that connect the mussel to a hard surface on one end — is composed of stiff material, whereas the remaining 20 percent, at the end that is affixed to the mussel itself, is soft and stretchy. The combination of these different material properties likely helps the mussels adhere to surfaces, and enables them to survive the impact of various forces.

“It turns out that the … 20 percent of softer, more extensible material is critical for mussel adhesion,” Zhao Qin, a research scientist at MIT, said in a statement.

Researchers have studied byssus threads before, but Qin and his colleagues wanted to observe how these threads, and all their connecting parts, operate in simulated wave conditions.

“We figured there must be something else going on,” Markus Buehler, head of MIT’s department of civil and environmental engineering, said in a statement. “The adhesive is strong, but it’s not sufficient.”

The researchers placed an underwater cage in Boston Harbor for three weeks to see how mussels attached themselves to glass, ceramic, wood and clay surfaces. In the lab, the scientists used a tensile machine to test the strength of byssus threads as they were pulled and deformed.

Even though byssus threads have both stiff and stretchy properties, the filaments are made of a protein closely related to collagen, the researchers said. From their experiments, the scientists discovered that the distribution of stiffness along the threads is critical to their effectiveness.

Understanding how byssus threads work could help scientists design synthetic materials with similarly flexible properties, such as surgical stitches that connect tissues together. The findings could also help in the development of new building materials, sensors for underwater vehicles and other equipment that could be subjected to extreme conditions, the researchers said.


DHA in fish oil can sooth and prevent neuropathic pain

DURHAM, N.C. — Physicians and patients who are wary of addiction to pain medication and opioids may soon have a healthier and more natural alternative.

A Duke University study revealed that a derivative of DHA (docosahexaenoic acid), a main ingredient of over-the-counter fish oil supplements, can sooth and prevent neuropathic pain caused by injuries to the sensory system. The results appear online in the Annals of Neurology.

The research focused on a compound called neuroprotectin D1=protectin D1 (NPD1=PD1), a bioactive lipid produced by cells in response to external stimuli. NPD1=PD1 is present in human white blood cells, and was first identified based on its ability to resolve abdominal and brain inflammation.

“These compounds are derived from omega-3 fatty acids found in fish oil, but are 1,000 times more potent than their precursors in reducing inflammation,” said Ru-Rong Ji, professor of anesthesiology and neurobiology at Duke University Medical Center and principal investigator of the study.

The team used laboratory mouse models of nerve injuries to simulate pain symptoms commonly associated with post-surgical nerve trauma. They treated these animals with chemically-synthesized NPD1=PD1, either through local administration or injection, to investigate whether the lipid compound could relieve these symptoms.

Their findings revealed that NPD1=PD1 not only alleviated the pain, but also reduced nerve swelling following the injuries. Its analgesic effect stems from the compound’s ability to inhibit the production of cytokines and chemokines, which are small signaling molecules that attract inflammatory macrophages to the nerve cells. By preventing cytokine and chemokine production, the compound protected nerve cells from further damage. NPD1=PD1 also reduced neuron firing so the injured animals felt less pain.

Ji believes that the new discovery has clinical potential. “Chronic pain resulting from major medical procedures such as amputation, chest and breast surgery is a serious problem,” he said. Current treatment options for neuropathic pain include gabapentin and various opioids, which may lead to addiction and destruction of the sensory nerves.

On the other hand, NPD1=PD1 can relieve neuropathic pain at very low doses and, more importantly, mice receiving the treatment did not show signs of physical dependence or enhanced tolerance toward the lipid compound.

“We hope to test this compound in clinical trials,” Ji said. The initial stages of the trial could involve DHA administration through diet and injection. “DHA is very inexpensive, and can be converted to NPD1 by an aspirin-triggered pathway,” he said. The ultimate goal is to develop a safer approach to managing chronic pain.



ImageImage credit: Ru-Rong Ji and Zhen-Zhong Xu, Duke University Medical Center

Family tree of fish yields surprises

The mighty tuna is more closely related to the dainty seahorse than to a marlin or sailfish. That is one of the surprises from the first comprehensive family tree, or phylogeny, of the “spiny-rayed fish,” a group that includes about a third of all living vertebrate species. The work is published July 15 in the journal Proceedings of the National Academy of Sciences.

The spiny-rayed fish are an incredibly diverse group, including tuna and billfish, tiny gobies and seahorses, and oddities such as pufferfish and anglerfish. The fish occupy every aquatic environment from coral reefs and open oceans to lakes and ponds. It includes all the major commercially fished species — all of which are threatened. But until now, no one has had any idea exactly how more than 18,000 species in 650 families are related to each other, said Peter Wainwright, professor and chair of evolution and ecology at the University of California, Davis and senior author on the paper.

“There has been a ‘bush’ at the top of the family tree leading to the rest of the vertebrates,” Wainwright said. “Now we have this beautiful phylogeny of one-third of all vertebrates.”

The study also shows that after roaring along for their first 100 million years, the pace of evolution of the spiny-rayed fish downshifted about 50 million years ago.

Some groups of fish have gone along steadily for millennia; others have gone through bursts of rapid evolution. Overall, the researchers found that the rate at which new species formed was fairly constant across the group from their origin to about 50 million years ago, then dropped about five-fold and has remained at that level since.

That might mean that these fish have essentially filled the available spaces, Wainwright said.

“It’s not uncommon in evolution to see a rapid diversification followed by a slowdown, but it’s never been seen on such a scale before,” he said.

Wainwright’s laboratory worked with the lab of Tom Near, a former postdoctoral scholar at UC Davis now at Yale University, and colleagues at the University of Tennessee, The Field Museum in Chicago, Florida Atlantic University and CUNY Staten Island to construct the family tree. Matt Friedman, a paleontologist at the University of Oxford, England, added fossils that helped set dates for branches of the tree.

The researchers looked at 10 genes in more than 500 fish species representing most of the families of spiny-rayed fish. They used the genetic data to construct a tree, grouping related families together. They also looked at the pace of evolution — the rate at which new species formed — in different branches, and across the group as a whole.

The spiny-rayed fish originated about 150 million years ago, separating from more primitive fish, such as lampreys, sharks and sturgeon, and from the ancestors of salmon and trout. Since then, they have spread into every aquatic habitat on Earth.

The tree shows some interesting relationships. For example, tuna are more closely related to seahorses than to swordfish or barracuda. The oddly shaped pufferfishes are related to anglerfish, the only fishes whose bodies are wider than they are deep.

Cichlids, a family that includes about 2,000 species of freshwater fish known for brooding their young in their mouths and a favorite for studies of evolution, are related to the engineer gobies, an obscure family of just two species that live on coral reefs and raise their young in a nest.

Wainwright’s special interest is in the evolution of fish jaws. Fish have two sets of jawbones, an outer jaw and “pharyngeal jaws” in the throat that adapted to different functions. In some fish, the lower pharyngeal jaw is fused into a single solid bone that can be used to crush prey such as shellfish.

Biologists had assumed that this fused jaw had evolved once and then spread into different groups of fish. Instead, the new tree shows that this structure evolved at least six times in different groups of fish.

Additional collaborators on the project were: Samantha Price at UC Davis; Alex Dornburg, Ron Eytan and Kristen Kuhn at Yale University; Leo Smith at the Field Museum; Jon Moore, Florida Atlantic University; and Frank Burbrink, College of Staten Island/CUNY, Staten Island. Funding was provided by the National Science Foundation.

[Original article]

1 Serving of Fish Weekly May Lower Anxiety During Pregnancy

By Bahar Gholipour, Staff Writer  

Eating at least some fish during pregnancy may lower women’s risk of anxiety, a new study suggests.

In the study, women who never or rarely ate dark or oily fish (such as tuna and salmon) were 53 percent more likely to have high levels of anxiety in their third trimester of pregnancy, compared with women who ate fish at least once a week.

The researchers also found that among vegetarian women, those who had the strictest diets were 25 percent more likely to have anxiety, compared with women who followed more flexible vegetarian diets and occasionally consumed fish or meat.

The link between higher fish consumption and lower risk for anxiety may be due to the omega-3 fatty acids in fish, the researchers said, writing in their study published July 12 in the journal PLOS ONE.

While stress is not uncommon in pregnant women, studies have linked high levels of anxiety to babies being born prematurely or with low weight.

“In order to have a healthy pregnancy, women need to follow a healthy diet, and not something special for pregnancy,” said study author Juliana Vaz, a researcher at the Federal University of Pelotas in Brazil. A healthy diet can include whole grains, vegetables, meat, poultry and fish, she said.

Some fish and seafood are good sources of omega-3 fatty acids, which are among the nutrients that cannot be made by the body, and must be obtained from diet.

Scientists have been studying the role of omega-3 in the body and how it affects different organs, including the heart and brain.

“We continue to see consistent data from many studies, suggesting that omega-3s have an impact on a range of behavioral disorders such as depression, anxiety, or schizophrenia,” said Dr. Ski Chilton, professor of physiology and pharmacology at Wake Forest University, who was not involved in the study.

Because of the demands of a growing fetus, pregnant women need higher amounts of nutrients. The lack of fish and meat in a vegetarian diet may explain why vegetarian women in the study tended to experience more anxiety, the researchers said.

“In this study, the vegetarian group did not fare well at all. The fetus’s brain is growing dramatically, and the fetus is getting all the omega-3s that are being produced,” Chilton said.

The study involved more than 9,500 women, who the researchers grouped based on their dietary patterns. One group was labeled the “health-conscious” group, and included women who mainly ate fruits, salad, fish and cereals. The “traditional” group’s diet consisted mainly of vegetables, red meat and chicken. Other groups were vegetarians, women who ate large amounts of processed food, and women who had a diet rich in sweets.

At the 32 weeks of pregnancy, the women completed questionnaires, and those who scored in the top 15 percent were classified as having high levels of anxiety.

It’s not exactly clear how low omega-3s in diet may result in anxiety, but it could be that low omega-3s in the blood may disrupt communication between cells, and affect how the body responds to psychological stress, the researchers said.

While low dietary omega-3s may exacerbate anxiety outside of pregnancy as well, as suggested by previous research, the effects may be more pronounced during pregnancy. Because of the nutritional demands of the fetus, a pregnant woman may experience a more severe omega-3 deficiency, Chilton said.

Pregnant women should avoid eating fish that contains high levels of mercury, such as tilefish, swordfish, king mackerel and shark. It is safe to eat up to 12 ounces a week (the equivalent of two average meals) of a variety of fish lower in mercury, such as salmon, pollock, catfish and canned light tuna, according to the U.S. Food and Drug Administration and the Environmental Protection Agency.

(Original article:

ImageCooked Atlantic salmon

Do Fish Feel Pain?

Do fish feel pain? The question is as old as angling itself, but it has never been answered definitively.

A recent study now concludes that fish lack the necessary pain receptors in their brains to experience pain the way humans and other animals do.

While fish have nociceptors — sensory receptors that respond to physically damaging objects and events by sending warning signals to the brain — these receptors don’t function in the same way in fish as they do in humans, according to the study’s authors.

“Even if fishes were conscious, it is unwarranted to assume that they possess a humanlike capacity for pain,” the authors of the study, published in the latest issue of Fish and Fisheries, wrote in the study’s abstract.

The researchers claim that one group of nociceptors, known as C-fiber nociceptors, is responsible for pain in humans but is rare in finned fishes and absent in sharks, ray and skates.

Another group of nociceptors, the A-delta nociceptors, evokes a simple, reflexive avoidance response that’s fundamentally different from genuine pain, the researchers wrote.

Critics, however, say the scientists are ignoring several other studies that contradict their findings.

In a 2003 study, fish were injected in the lips with bee venom or an acid solution. The fish reacted immediately, rubbing their lips on the side or bottom of their tank, rocking from side to side and breathing at a rate comparable to that of a fish swimming at top speed, New Scientist reports.

And a 2009 study found that after experiencing a painful event, fish demonstrated defensive or avoidance behaviors, indicating the fish felt pain and remembered it.

“There are a number of studies which we believe provide enough evidence to show that fish do feel pain, and this remains our view,” a spokesman for the Royal Society for the Prevention of Cruelty to Animals (RSPCA) told The Telegraph.

The argument over fish feeling pain has driven a wedge between anglers and animal-rights activists, but one of the study’s authors feels the divisive debate is unproductive.

“I think that fish welfare is very important, but I also think that fishing and science is too,” Robert Arlinghaus of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin, told The Telegraph.

“There are many conflicts surrounding the issue of pain and whether fish can feel it, and often, anglers are portrayed as cruel sadists,” Arlinghaus said. “It’s an unnecessary social conflict.”

(Original article on



200-Year-Old Rockfish Caught Off Alaska

In 1813, President James Madison occupied the White House, Americans occupied Fort George in Canada (a result of the War of 1812) and a rockfish was born somewhere in the North Pacific.

Two hundred years later, that same rockfish was caught off the coast of Alaska by Seattle resident Henry Liebman — possibly setting a record for the oldest rockfish ever landed.

Troy Tydingco of the Alaska Department of Fish and Game told the Daily Sitka Sentinel that the longevity record for the shortraker rockfish (Sebastes borealis) is 175 years, but that fish “was quite a bit smaller than the one Henry caught.”

“That fish was 32-and-a-half inches [83 centimeters] long, where Henry’s was almost 41 inches [104 cm] — so his could be substantially older,” Tydingco said.

Samples of the rockfish have been sent to a lab in Juneau, where the actual age of Liebman’s fish will be determined, according to the Sentinel.

Scientists can estimate the age of a fish by examining an ear bone known as the otolith, which contains growth rings similar to the annual age rings found in a tree trunk.

Animal longevity remains a puzzle to biologists. Some researchers have found that smaller individuals within a species tend to live longer than their bigger brethren. This may be due to the abnormal cell growth that accompanies both larger body size and the risk of cancer.

The longest-lived animal ever found was a quahog clam scooped from the waters off Iceland. The tiny mollusk was estimated to be 400 years old.

At 39.08 pounds (17.73 kilograms), Liebman’s fish may also set a record for the largest rockfish ever caught.

“I knew it was abnormally big, [but I] didn’t know it was a record until on the way back — we looked in the Alaska guidebook that was on the boat,” Liebman told the Sentinel.

He plans to have the fish mounted,  so he can continue to tell the fish story that he’s already been “getting a lot of mileage” out of, according to the Sentinel.

(Original article on