University of Exeter

Scientists at the University of Exeter and Texas A&M University found that when fish fight over food, it is personality, rather than size, that determines whether they will be victorious. This is a sheepshead swordtail fish.

By Denise Chow
LiveScience

When fish fight over food, don't count the little guy out.
In hostile situations, a fish's personality — including how aggressive it acts — may matter more than size, according to new research.

The researchers from the University of Exeter in the United Kingdom and Texas A&M University in College Station studied how small fish managed relative to their larger peers when it came time for feeding. They found that small fish that exhibited aggressive behavior fared well in the feeding contests, regardless of their smaller stature.

"We wondered if we were witnessing a form of Napoleon, or small man, syndrome," Alastair Wilson, an evolutionary ecologist in the department of biosciences at the University of Exeter, said in a statement.

The findings, published in the April 2013 issue of the journal Behavioral Ecology and Sociobiology, indicate that the strength of a fish's personality may be crucial when food is scarce.

"Certainly our study indicates that small fish with an aggressive personality are capable of defeating their larger, more passive counterparts when it comes to fights over food," Wilson said. "The research suggests that personality can have far-reaching implications for life and survival."

Wilson and his colleagues paired up smaller and larger sheepshead swordtail fish (Xiphophorus birchmanni), and monitored their behavior when food was added to the tank. Fish that were more aggressive, regardless of size, were consistently the ones that won the food and subsequently gained weight, the scientists explained.

The males were more inclined to attack the other fish to win the food, whereas females were less aggressive overall, and rarely attacked their opponent, the researchers found.

According to the researchers, none of the fish were distressed or sustained physical injuries during the experiments.

An animal's "personality" is characterized if it consistently displays an observed behavior, given certain conditions or environments, the researchers said. Previous studies have suggested that aspects of an animal's personality may be inherited. As such, the researchers are keen to examine whether aggressive behavior in feeding is tied to reproductive success, and ultimately how these factors influence the heritability of certain personality traits.  

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook and Google+. Original article on LiveScience.com.

• Image Gallery: Freaky Fish
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Aquamarine Fukushima

An African coelacanth, photographed using a Remotely Operated Vehicle off the coast of Tanga, Tanzania.

The genome of the coelacanth, an ancient-looking lobed-finned fish, has been sequenced and is already providing insight to the evolutionary changes that allowed the first four-limbed animals, called tetrapods, to crawl out of the water and on to land.

The sequence and preliminary analysis, reported Thursday in the journal Nature by a team spanning 40 research institutions and 12 countries, is a "massive piece of work," Xiaobo Xu, a paleontologist at Kean University who was not involved in the effort, told NBC News in an email.

"The paper really provides rare and valuable genomic data for offering heavy-weight opinions on issues bearing on the fish (to) tetrapod transition," he said.

It also settles a debate that has long raged amongst evolutionary biologists: what fish is the closest relative of tetrapods: the coelacanth or the equally odd-looking lobed-finned lungfish. The winner, according to analysis of the newly-published genome, is the lungfish.

"We think we have definitively shown it now," Jessica Alföldi, a research scientist at the Broad Institute of MIT and Harvard and co-first author of the paper, told NBC News. "They are very close, which is why it took so much data to figure it out."

Slow evolving genes
Scientists thought coelacanths went extinct about 70 million years ago, during the Late Cretaceous period. That changed when a fish trawler off the South African coast delivered a fresh-caught coelacanth to a local natural history museum in 1938, proving that the fish are alive and well.

The coelacanths' odd, ancient-looking looks raised eyebrows and earned it the nickname "living fossil" — much to the chagrin of evolutionary biologists, noted Alföldi. ("It makes people think there was no evolution," she explained.)

Analysis of the coelacanth genome reveals that the ancient fish is indeed evolving just about as quickly as all vertebrates in every aspect except one: its genes, the stretches of protein that code for specific functions.

Other aspects, such as the amount of transposable elements — so-called "junk DNA" — that jump around the genome, is about the same as other species, a sign of evolution. In addition, big chunks of DNA are constantly being rearranged. 

"But if we look at the proteins and say how much have these proteins changed in the last 400 million years, they have changed more in us than in the coelacanths, and they have changed a lot more in pretty much every other vertebrate species that we looked at," Alföldi said.

Why? 

One speculation is that coelacanths haven't needed to evolve, Alföldi said. They live in deep sea caves and appear to have few predators or competitors for food.

Fin to limb
Comparisons of the coelacanth genome with other vertebrates allows researchers to see what genes were lost and regulatory elements gained as lobed-finned fish crawled out of the sea and on to land. 

Some of the preliminary findings are expected, such as a suite of changes to regions of the genome that control limb development, for example. 

"This is consistent with the hypothesis that the autopod (the hand and digits) of land-living vertebrates is a modification of features already present in lobe-finned fishes, rather than something that arose entirely de novo," Matt Friedman, a paleobiologist at Oxford University, said in an email to NBC News.

Others, however, were unexpected, though "end up making total sense once you think about it," Alföldi said.

For example, genes related to smell exhibit a wide range of changes as vertebrates came on to land, which make sense given that smelling underwater is different than on land, she noted. Other changes are seen in sections of the genome that regulate immunity and the way fish and land animals poop.

For Friedman, who was not involved with the team, the findings are in line with decades of paleontological and anatomical studies of the coelacanths and other lobe-finned fish.

"Apart from specific genetic details — which are of course new — most of what is here seems to corroborate our current ideas about evolutionary changes associated with the origin of terrestriality," he said.

The specific genetic details will allow members of the research team and the broader scientific community to better understand what Yu called "the unique genomic features that shed light on the shared evolutionary past of lobe-finned fish and tetrapods."

John Roach is a contributing writer to NBC News. To learn more about him, visit his website. 

Wakasa History and Folklore Museum, Fukui, Japan

Early humans were cooking fish 12,000 years ago in pots like this reconstructed early vessel from Torihama, Japan.

In the chilly final years of the last ice age, hunting communities in Japan may have served up warm fish stews of salmon and shellfish for dinner. 

In charred scrapings from clay pots dating back to the Jomon period 15,000 years ago, scientists found well-preserved traces of fat from marine and freshwater fish and shellfish. The pots themselves are among the oldest clay vessels found anywhere, but until now, no one could confirm what they were used for. 

"It is the oldest example of cooking in pottery," Oliver Craig, a senior lecturer in archaeology at the University of York,  told NBC News. Craig is the lead author of a research paper on the pots appearing in Thursday's issue of the journal Nature.

Even older clay vessels have been found in China, but pinpointing their age has been difficult.

The flakes of burnt pottery have introduced archaeologists to a Stone Age society that stewed their fish and ate it in groups, going against the stereotype of Stone Age humans as hunters and gatherers. The researchers analyzed up to 30 milligrams of burnt remains from 101 vessels that were found at 13 different sites.

Cooking pots would have come in handy as early humans struggled to survive during the last ice age. "It seems like pottery in Japan was innovated during the coldest periods, which is what you might expect," Craig says. Because the oldest pots from the Jomon sites, the pots that date back 15,000 years, are fairly rare, he guesses that fish stewing may have been part of a feasting ritual.

If that's true, the clay vessels didn't merely serve a functional role as cooking vessels. They also brought people together. "I would say that through most of human history, eating has always been an important social activity," Simon Kaner, head of the Center for Archaeology and Heritage at the Sainsbury Institute for the Study of Japanese Arts and Cultures, told NBC News.

Tokamchi City Museum

This 15,000 year-old pot is from Kubodera-minami, Niigata Prefecture, Japan.

The pots may not have been reserved exclusively for special occasions. "The use of pots would have facilitated such communal meals, as well as experimentation with all sorts of different ways of cooking based on aquatic resources like fish stews," Peter Bogucki, an archaeologist at Princeton University, told NBC News in an email. Bogucki believes the pots may have been part of regular life, especially in the later years of the Jomon period. According to Kaner, the hunters of that period ate a range of natural foods and had a deep knowledge of the plants and animals around them. 

Old clay pots from around the world are gradually revealing the eating habits of ancient people. Neolithic cattle-rearing communities in Europe made soft, unfermented cheese 7,500 years ago in sieve-like pots. Fragments of those vessels found in Poland contained incriminating traces of milk fats. Similarly, traces of dairy fat from vessels found in Africa suggests that humans began making yogurt on that continent around the same time. 

More on ancient eating habits: 

• Say cheese! Central European farmers did, 7,500 years ago
• Israeli researchers find ancient disposable cutlery
• Piles of ancient pottery unearthed in Greece

Nidhi Subbaraman writes about science and technology. Follow her on Twitter and Google+. 

Robert Sansom

The Euphanerops sported bizarre fins below its anus, revealing some of the odd turns evolution took on the path to vertebrate evolution.

By Tia Ghose, LiveScience

A 370-milion-year-old, primitive fish sported a weird pair of fins just below its anus, new research shows.

The strange appendages, detailed Tuesday in the journal Biology Letters, were found on an ancient jawless fish called Euphanerops longaevus that lived around the time that jawless fishes like lampreys split off from jawed vertebrates, which include everything from sharks to humans.

"What's weird about this organism is that it had a paired anal fin. It's unique — no other known fossil or modern fish is known to have that disposition," said study co-author Robert Sansom, a paleontologist at the University of Manchester in the U.K.

The findings suggest that early in primitive vertebrates' history, evolution experimented with a number of wacky body plans, only some of which survived, Sansom told LiveScience. [Image Gallery: The Freakiest Looking Fish]

Early fish
The Euphanerops fish were 3.9 inches long and looked somewhat like modern-day eels. The specimens were unearthed in a fossil bed in Miguasha, Quebec, decades ago, and were stored in collections in the National History Museum in London and the Museum d'Histoire Naturelle, Miguasha, in Quebec.

Previously, researchers weren't sure exactly what to make of the creatures' weird fins. Some thought the anal appendages might actually have been displaced from another part of the animal's body in the fossilization process.

Early body plan
The researchers weren't convinced of the displacement explanation. By comparing the 3-D surfaces of the fossil under a microscope, the team concluded that the fin pair was actually located below the anus on the living creature. Though it's not clear exactly how the fins were used, the fins most likely helped the fish get around, Sansom said.

The fossil dates to a critical period of vertebrate evolution: Jawed and jawless vertebrates diverged roughly around this time. Eventually jawed fish developed paired fins (but not anal fins) that evolved to become arms and legs. In fact, the same genes code for shark fins and human limbs.

The discovery changes the view of how fishes were evolving at this time, Sansom said.

"Rather than gradual acquisition of complex characteristics, maybe there was a bit more experimentation and odd acquisitions," he said.

Specialized trait?
The finding of paired anal fins is "beautifully illustrated," said Michael Coates, a vertebrate paleontologist at the University of Chicago, who was not involved in the study.

"It might just be the first vestige, it might be some kind of precursor to generating paired fins" that are commonly seen throughout jawed vertebrates, Coates told LiveScience.

But it's also possible they were a specialized trait that only Euphanerops possessed, not reflective of the evolutionary history of jawed vertebrates as a whole, Coates said.

Follow Tia Ghose on Twitter @tiaghose. Follow LiveScience@livescience,Facebook &Google+. Original article on LiveScience.com.

• Image Gallery: 25 Amazing Ancient Beasts
• Top 10 Useless Limbs (and Other Vestigial Organs)
• In Photos: Spooky Deep-Sea Creatures
  

Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Bent Christensen / AP file

Calling their results alarming, the Swedish researchers who did the study suspect the little drugged fish could become easier targets for bigger fish because they are more likely to venture alone into unfamiliar places.

By Jeff Donn, Associated Press

BOSTON —  What happens to fish that swim in waters tainted by traces of drugs that people take? When it's an anti-anxiety drug, they become hyper, anti-social and aggressive, a study found. They even get the munchies.

It may sound funny, but it could threaten the fish population and upset the delicate dynamics of the marine environment, scientists say.

The findings, published online Thursday in the journal Science, add to the mounting evidence that minuscule amounts of medicines in rivers and streams can alter the biology and behavior of fish and other marine animals.

"I think people are starting to understand that pharmaceuticals are environmental contaminants," said Dana Kolpin, a researcher for the U.S. Geological Survey who is familiar with the study.

Calling their results alarming, the Swedish researchers who did the study suspect the little drugged fish could become easier targets for bigger fish because they are more likely to venture alone into unfamiliar places.

"We know that in a predator-prey relation, increased boldness and activity combined with decreased sociality ... means you're going to be somebody's lunch quite soon," said Gregory Moller, a toxicologist at the University of Idaho and Washington State University. "It removes the natural balance."

Researchers around the world have been taking a close look at the effects of pharmaceuticals in extremely low concentrations, measured in parts per billion. Such drugs have turned up in waterways in Europe, the U.S. and elsewhere over the past decade.

They come mostly from humans and farm animals; the drugs pass through their bodies in unmetabolized form. These drug traces are then piped to water treatment plants, which are not designed to remove them from the cleaned water that flows back into streams and rivers.

The Associated Press first reported in 2008 that the drinking water of at least 51 million Americans carries low concentrations of many common drugs. The findings were based on questionnaires sent to water utilities, which reported the presence of antibiotics, sedatives, sex hormones and other drugs.

The news reports led to congressional hearings and legislation, more water testing and more public disclosure. To this day, though, there are no mandatory U.S. limits on pharmaceuticals in waterways.

The research team at Sweden's Umea University used minute concentrations of 2 parts per billion of the anti-anxiety drug oxazepam, similar to concentrations found in real waters. The drug belongs to a widely used class of medicines known as benzodiazepines that includes Valium and Librium.

The team put young wild European perch into an aquarium, exposed them to these highly diluted drugs and then carefully measured feeding, schooling, movement and hiding behavior. They found that drug-exposed fish moved more, fed more aggressively, hid less and tended to school less than unexposed fish. On average, the drugged fish were more than twice as active as the others, researcher Micael Jonsson said. The effects were more pronounced at higher drug concentrations.

"Our first thought is, this is like a person diagnosed with ADHD," said Jonsson, referring to attention deficit-hyperactivity disorder. "They become asocial and more active than they should be."

Tomas Brodin, another member of the research team, called the drug's environmental impact a global problem. "We find these concentrations or close to them all over the world, and it's quite possible or even probable that these behavioral effects are taking place as we speak," he said Thursday in Boston at the annual meeting of the American Association for the Advancement of Science.

Most previous research on trace drugs and marine life has focused on biological changes, such as male fish that take on female characteristics. However, a 2009 study found that tiny concentrations of antidepressants made fathead minnows more vulnerable to predators.

It is not clear exactly how long-term drug exposure, beyond the seven days in this study, would affect real fish in real rivers and streams. The Swedish researchers argue that the drug-induced changes could jeopardize populations of this sport and commercial fish, which lives in both fresh and brackish water.

Water toxins specialist Anne McElroy of Stony Brook University in New York agreed: "These lower chronic exposures that may alter things like animals' mating behavior or its ability to catch food or its ability to avoid being eaten — over time, that could really affect a population."

Another possibility, the researchers said, is that more aggressive feeding by the perch on zooplankton could reduce the numbers of these tiny creatures. Since zooplankton feed on algae, a drop in their numbers could allow algae to grow unchecked. That, in turn, could choke other marine life.

The Swedish team said it is highly unlikely people would be harmed by eating such drug-exposed fish. Jonsson said a person would have to eat 4 tons of perch to consume the equivalent of a single pill.

Researchers said more work is needed to develop better ways of removing drugs from water at treatment plants. They also said unused drugs should be brought to take-back programs where they exist, instead of being flushed down the toilet. And they called on pharmaceutical companies to work on "greener" drugs that degrade more easily.

Sandoz, one of three companies approved to sell oxazepam in the U.S., "shares society's desire to protect the environment and takes steps to minimize the environmental impact of its products over their life cycle," spokeswoman Julie Masow said in an emailed statement. She provided no details.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

© Clelia Gasparini

Guppies (Poecilia reticulata) are one of the few fish species to directly copulate during sex. Females of this species are promiscuous, and prefer flamboyant males with large spots of color on their bodies (shown here).

By Charles Choi, LiveScience contributor

Ugly friends can make you look better, at least if you're a guppy, researchers say.

Scientists investigated guppies (Poecilia reticulata), a common aquarium pet, and one of the few fish species to directly copulate during sex. Females of this species are promiscuous, and prefer flamboyant males with large spots of color on their bodies.

Recent theory suggests that in species where females prefer showy mates, males might prefer courting females that are surrounded by relatively drab males. In other words, males should prefer surroundings that make them look attractive.

To prove this theory, researchers experimented with wild-caught guppies from Trinidad. They had male guppies choose between two females surrounded by either a pair of drab males or a pair of males with large orange body spots. They also focused on whether males had prior experience courting females in the presence of competition or not.

The scientists found male preference for relatively unattractive competitors increased with experience, with experienced males spending about 62 percent of their time with females surrounded by relatively drab males, while more naive males spent only about 57 percent of their time with such females. Similar findings were seen when it came to females that males had previously observed surrounded by drab males.

In fact, as long as males were approaching females surrounded by even drabber males, their chance at getting some action increased.

"We believe we have showed how drab males can still be chosen by females — if they are able to exploit the right social context," researcher Clelia Gasparini, a behavioral ecologist at the University of Western Australia, told LiveScience. In other words, drab males can get sex if they discover females surrounded by even drabber males. [The Animal Sex Quiz]

These findings might hold true at times in other species, including humans, but further confirmatory research is needed. "Different outcomes for different species are not surprising — every species has peculiar mating systems," Gasparini said. For instance, choice of partners might not be based only on attractiveness, but other traits, such as the ability to provide parental care to offspring.

Past research found the reverse was apparently also true — that having a good-looking significant other will cause other potential mates to find a man or woman more desirable. Still, humans are different from guppies. For instance, monogamy is common with humans but not guppies, "and all together this makes our mating system quite complex to compare with the results in guppies," Gasparini said.

Future research can analyze how male guppies improve their courtship with experience, and how long they remember and can use knowledge of their rivals' quality, Gasparini said.

Gasparini and her colleagues Giovanna Serena and Andrea Pilastro detailed their findings online Feb. 13 in the journal Proceedings of the Royal Society B: Biological Sciences.

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• Top 10 Swingers of the Animal Kingdom
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Christian Mehlfuehrer / UC Davis

The highly invasive lionfish is easily available through aquarium and internet sales and represents a potential threat for California waters, according to a new report.

By John Roach, NBC News Digital

Exotic and colorful aquarium fish, such as those made famous by the Disney film "Finding Nemo," are escaping to the open ocean in real life and disrupting marine ecosystems, according to a new report on the spread of invasive species.

More than 11 million non-native aquarium fish and plants — from tropical fish to seaweed and snails, representing 102 species — are imported annually through the California ports of Los Angeles and San Francisco, the report found. 

Of those, 13 species have been introduced to California marine waters, most likely because they were released from aquariums. More than two thirds successfully made a home for themselves in California. 

The number of introduced invasive aquarium species is relatively low compared to those released via other means, such as ballast water released from ship hulls, but aquarium fish are grown to be hardy and robust, which makes them highly successful when they reach foreign waters.

"The aquarium trade species tend to be really bad actors," Susan Williams, a professor of evolution and ecology at the University of California at Davis, told NBC News. "We believe that that is in part due to the fact that they have to be so hardy to be able to survive the trade."

Williams is the lead author of the new report, one of six on the various ways marine invasive species are spread. It was prepared for the California Ocean Protection Council, a government agency. The results, she said, can be generalized to the rest of the world.

The problem of aquarium fish in marine ecosystems has been studied for several years, including work done more than a decade ago by Williams. What’s new here is that the researchers, for the first time, were able to examine data from U.S. Fish and Wildlife inspections, not just what was reported.

The data, in turn, will allow robust comparisons across the other ways invasive species are spread, such as ships and fish farms, and inform agencies on how best to combat the problem.

The new report focused on the killer algae Caulerpa and predatory lionfish, two well-known trouble makers in the aquarium trade. The algae, for example, infected two lagoons in Southern California in 2000 and cost $6 million to eradicate.

Lionfish were introduced to Florida in 1999 and spread throughout the Caribbean and up the East Coast by 2010. They are not yet in California waters, but are able to withstand cooler temperatures and if introduced could establish themselves in San Francisco bay, and further north as waters continue to warm.

"Lionfish are voracious predators in their native habitats, and in their invaded habitat any predator is a potential threat to the native ecosystem," Williams said.

Other aquarium trade species of particular concern include the ever popular green chromis, a damselfish that is being imported through California in large numbers. Even though they are not predators, damselfish are aggressive toward other fish, Williams said.

Preventing the spread of aquarium fish "is not rocket science," she said. Simple measures such as passing out brochures with proper disposal instructions at pet stores would help. Currently, this is not a widespread practice, she added.

"If people were just aware that they shouldn’t dump their aquariums in any natural waters," she said, "that goes a long way to averting this problem." 

John Roach is a contributing writer for NBC News Digital. To learn more about him, check out his website.

Takashi Maie

The Nopoli rock-climbing goby (Sicyopterus stimpsoni) uses the same muscles for feeding and climbing waterfalls.

By Charles Choi
LiveScience

 A waterfall-climbing fish in Hawaii uses the same muscles to both rise and feed, researchers have discovered.

Scientists looked at the Nopoli rock-climbing goby (Sicyopterus stimpsoni), also known in Hawaiian as o'opu nopili. This plant-eating fish is found throughout Hawaii, and was once greatly relished as food, apparently being a favorite snack among priests.

Many gobies can inch their way up waterfalls with the aid of a sucker on their bellies formed from fused pelvic fins. The Nopoli rock-climbing goby, on the other hand, can climb waterfalls as tall as 330 feet (100 meters) with the aid of a second mouth sucker, which develops after their mouthparts move from a forward-facing position to under the body during a two-day-long metamorphosis into adulthood.

"For a human to go the equivalent distance based on body size, it'd be like doing a marathon, some 26 miles (42 kilometers) long, except climbing up a vertical cliff-face against rushing water," researcher Richard Blob, an evolutionary biomechanist at Clemson University in South Carolina, told LiveScience. Indeed, an old Hawaiian saying is that as the Nopili clings, so will luck.

The goby, which can grow up to 7 inches (18 centimeters) long as an adult, feeds by cyclically sticking the tip of its upper jaw against rock to scrape food off surfaces. This behavior is quite distinct from other Hawaiian gobies, which feed by sucking in food from the water. Given the apparent similarity of the climbing and feeding behaviors of the S. stimpsoni species, researchers thought one might have developed from the other. [ See Video of Waterfall-Climbing Fish ]

"The fish gave us an opportunity to see how unusual behaviors evolved," Blob said.

To see if these behaviors really were as similar as they looked, the scientists captured Nopoli rock-climbing gobies from a stream on the island of Hawaii by net while snorkeling and kept them in aquaria.

They next filmed the gobies' jaw-muscle movements as the fish climbed and ate, either scraping food off glass microscope slides or climbing up angled plastic boards. They found that overall movements were indeed similar during both activities.

It remains uncertain whether feeding movements were adapted for climbing, or vice versa.

"To understand the sequence of steps in the evolution of this extreme behavior, we want to look at closely related species that do one of the behaviors, but not the other," Blob said. "This fish has relatives in many oceanic islands, such as the Caribbean."

The scientists detailed their findings online Friday in the journal PLOS ONE.

They will also present their findings Sunday at the Society for Integrative and Comparative Biology annual meeting in San Francisco.

Follow LiveScience on Twitter @livescience. We're also on Facebook  and Google+.

• The 10 Weirdest Animal Discoveries of 2012
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