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Guppies Can Help Fight Dengue

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MANILA, PHILIPPINES – Larvae-eating guppy fish can help combat the spread of dengue, a mosquito-borne illness giving rise to hundreds of thousands of severe cases including 20,000 deaths worldwide every year, according to a trial study by the Governments of Cambodia and the Lao People’s Democratic Republic (Lao PDR) with the support of the Asian Development Bank (ADB) and the World Health Organization (WHO).

“This is a low-cost, year-round, safe way of reducing the spread of dengue in which the whole community can participate,” said ADB health specialist Gerard Servais. “It offers a viable alternative to using chemicals and can reduce the scale of costly emergency response activities to contain epidemics.”

The community-based project, conducted in two districts in Cambodia and the Lao PDR from 2009 to 2011, resulted in a sharp decline in mosquito larvae in water storage tanks after the tiny fish were introduced. Guppies eat larvae that grow into mosquitoes, which in turn bite humans and transmit dengue.

Dengue causes severe joint and muscle pain, headache, high fever and rashes and is fatal in a small proportion of cases, in particular if not diagnosed and treated early. Outbreaks of the illness not only affect families with sudden health care costs and loss of incomes for adults put out of work, but also impact health services, businesses and tourism, straining government budgets due to unplanned spending on large-scale emergency response measures. Currently there is still no vaccine or specific medicine to treat this viral disease.

Around 2.5 billion people worldwide are at risk of contracting dengue, more than 70% of whom live in Asia and the Pacific. The threat of exposure to dengue-carrying mosquitoes is rising with uncontrolled urbanization and a surge in the use of non-biodegradable packaging, which can act as a water reservoir for dengue mosquito breeding. Dengue is spread by a specific mosquito that breeds readily in standing water, such as found in storage containers, flower pots and discarded tires. The guppies are particularly effective in these settings.

Convincing communities to accept fish in their water containers was a key element of the project. The trial showed that guppies do not harm water quality and can survive on microscopic organic material in the absence of mosquito larvae. At the project close in Cambodia, about 88% of the storage containers contained guppies, with the figure at 76% in Lao PDR.

“The project was successful in mobilizing communities with widespread grassroots participation, and high levels of acceptance of fish as an effective way of reducing the spread of dengue,” said Dr. Eva Christophel, a WHO specialist in vectorborne diseases. “This project was an important contribution to WHO’s efforts to develop a toolkit of different community-based methods to prevent and reduce the magnitude of dengue transmission.”

ADB provided financing of $1 million for the project.

– See more at: ResearchSea

Posted September 13th, 2013.

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How and Why Fish Swim in Schools

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Photo by Thomas P. Quinn.

SEATTLE – Sept. 12, 2013 – How and why fish swim in schools has long fascinated biologists looking for clues to understand the complexities of social behavior. A new study by a team of researchers at Fred Hutchinson Cancer Research Center may help provide some insight.

To be published online in the Sept. 12 issue of Current Biology, the study found that two key components of schooling – the tendency to school and how well fish do it – map to different genomic regions in the threespine stickleback, a small fish native to the Northern Hemisphere.

That’s important, said lead author Anna Greenwood, Ph.D., because it suggests that if researchers can identify the genes that influence the fishes’ interest in being social, they may be closer to understanding how genes drive human social behavior.

“The motivation to be social is common among fish and humans,” said Greenwood, a staff scientist in the Human Biology Division at Fred Hutch. “Some of the same brain regions and neurological chemicals that control human social behavior are probably involved in fish social behavior as well.”

‘Some kind of genetic factor’ controlling behavior

Greenwood and several colleagues in the Peichel Labat Fred Hutch have been studying sticklebacks for several years to understand the genesis of natural variation. In a previous study, they found that a group of marine sticklebacks from the Pacific Ocean in Japan schooled strongly, while a second group from a lake in British Columbia preferred hiding out and were less able to maintain the precisely parallel formation required for schooling.

Though both groups were raised in identical lab conditions, they behaved differently from each other when placed together in a schooling situation.

“That really suggests that there’s some kind of genetic factor controlling this difference,” Greenwood said.
This time around, the researchers used lab-raised hybrids of the strongly schooling, saltwater-dwelling marine sticklebacks and the schooling-averse sticklebacks that live in freshwater.

Alison Bell, Ph.D., an associate professor of animal biology at the University of Illinois, Urbana-Champaign, said the linking of behaviors to different genomic regions in the same species – and in particular, social behavior that depends on the behavior of others – makes the study especially compelling.

“I think that’s very significant,” she said. “It’s been hard to find regions of the genome that are associated with any kind of behavioral traits in natural populations. Behavior is very plastic and it’s subject to environmental influences, so it’s been really tricky to do that.”

Hans Hofmann, Ph.D., a professor of integrative biology at the University of Texas at Austin, said the study also refutes the assertion that human behavior is too complex to understand.

“I think it shows that even such complex behaviors associated with other individuals in a very rigid and organized manner can be dissected genetically,” he said. “Studies like this tell us that we might get there eventually.”

Old bicycle wheel and lab motor used in experiment

Fish school primarily for protection from predators, and also to make swimming and foraging more efficient. Schools of fish in the wild are dynamic and fluid, but for both studies the Fred Hutch researchers had to create an environment in which they could observe the fish in unchanging conditions.

Building the device used for both experiments proved a challenge. The researchers suspended an old bicycle wheel above a circular acrylic tank and found a motor from an old lab shaker that could turn the wheel, but were stumped about how to connect them.

Greenwood and co-author Abigail Wark scoured craft shops and hardware stores looking for a suitable part, trying everything from plastic bra straps to necklaces before finding some silicone tubing that worked.
“It was a few weeks of going around to shops,” Greenwood said.

They made a mold to create model fish from resin tinted with grey pigment, dabbing on eyes with black paint to make them look more realistic. The eight models (they found that eight is the minimum number to get fish to school in a lab setting) were suspended from the bike wheel with wire.

Beyond its findings connecting specific behaviors with genomic regions, the study also found that the same regions of the genome appear to control both the stickleback’s ability to school as well as the anatomy of its lateral line, a system of organs that detect movement and vibration in water, and contain the same sensory hair cells found in the human ear.

That suggests a single gene could cause fish to detect their environment differently, Greenwood said, and supports the long-held notion that schooling behavior is controlled in part by the lateral line.

It provides a promising starting point in trying to locate the gene involved, and Fred Hutch researchers are now working on manipulating the gene they think causes changes in the stickleback’s lateral line to see if that alters the fishes’ schooling behavior.

Research on schooling behavior in fish may seem an odd fit for a cancer research center, but Greenwood said natural variation can influence not just behavior, but also susceptibility to illness and disease.

“If we can understand the process by which evolution works and the genes that tend to be affected during evolution in these other model systems, we can apply that to humans,” she said.

Source: Fred Hutchinson Cancer Research Center

Posted September 12th, 2013.

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The Ocean as a Cure All

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Tackling the risks of infection and other illnesses remains a challenge. Might the solution come from the sea?

The life that inhabits the world’s oceans has almost infinite variety. It remains an untapped source of diversity. “The oceans can be deep or shallow, they can be more or less tidal, and they can include unique environments such as volcanic vents,” says Brian McNeil of Strathclyde University in Scotland, UK. “That means that the life that lives there has huge diversity. We have only very limited knowledge of it, and especially of the microbial life forms that are found in the ocean,” he adds.

The SeaBioTech project, started in 2012, is intended to close some of these knowledge gaps by looking in the seas and oceans around the globe for life forms with novel properties. The aim is to find raw material for the world’s biotechnology industry, with a particular emphasis on antibiotics and other medical compounds. “Think about marine sponges,” says McNeil, who is coordinator for the project. “They are vulnerable to predators and to attack by fungi and bacteria, but they don’t seem to suffer much from their attacks. This is partly because they have an internal coating, the biofilm, which contains protective microbial species. We think that these microbes make compounds which deter fungi and bacteria.”

The plan is for the project to sample organisms from a wide range of marine environments, ranging from the cold Atlantic sea off Scotland to the volcanically-active region near the Mediterranean island of Santorini. The sea there is so deep that a remotely-operated submarine will be used to gather samples. “Enzymes and microbes that can survive temperatures of over 70˚C, and high levels of toxicity, could be of interest to biotechnology, perhaps for detoxifying land or water,” McNeil tells youris.com.

He adds that the less romantic phase of the project, the lab work that will follow the sample-gathering, will also be the difficult part. The approach is to search for interesting gene sequences as well as for antibiotic activity. Antibiotics are an especially important target for the project, because of growing bacterial resistance to existing antibiotics. In addition, there could be compounds of interest as additives for cosmetics, or for wound healing. There could also be new vaccines for the fast-growing global fish industry. At the moment, farmed fish are plagued by sea lice and other parasites. The project could lead to fish vaccines that are less polluting than those used today.

Some experts perceive the project as an original initiative and praise its unprecedented scale. “While we have appreciated the importance of marine organisms, genetics and biochemistry since the 1970s,” says Frank Koehn, research fellow for natural products and world-wide medicinal chemistry at the pharmaceutical corporation Pfizer, based in Groton, Connecticut, USA, “we now recognise more clearly that microbes and larger organisms are an untapped source of genetic diversity, and of compounds that can be important to human and animal health.” He adds that there are already anticancer drugs in use that were discovered in the marine environment.

What is more, “many species of marine microorganisms, algae and invertebrates have been shown to produce interesting small molecules,” says Camila Esguerra, lecturer at the laboratory for molecular biodiscovery at the University of Leuven in Belgium. She is involved in a completely separate EU-funded project in marine biodiscovery, calledPharmaSea. She points out that SeaBioTech is designed to discover how these molecules might work as pharmaceuticals. But it could be 10-15 years before the findings of this project turn into usable drugs or treatments.

Perhaps the project’s biggest problem may be the public acceptability of new compounds from the sea, according to Yvonne Armitage, sector lead for biosciences at the UK government’s biosciences knowledge transfer network, based at the Roslin Institute in Scotland. However, chemicals from the marine environment are already used in cosmetics, foods and nutraceuticals, so this issue should be manageable.

Finally, the political issue of intellectual property in the wild environment is another possible problem for a project of this type. Esguerra says that “an uncoordinated and complex mixture of legal domains” has jurisdiction over these resources… This includes theUN Convention on the Law of the Sea, the Convention on Biological Diversity, and a range of intellectual property rights law. In the past, universities and companies collected and used soil and water samples without payment, and without proper contracts to control the use that was made of them.

But Koehn, who is also an unpaid member of the scientific advisory board for the project, contends that more recently, progress has been made in this area. He concludes: “Nations now regard biodiversity as part of their wealth, and there is an understanding that it has to be paid for.”

Photo courtesy of Sean Nash

Source: CommNet

Posted September 9th, 2013.

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Fast-Lived Killies

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Photograph by Radim Blazek, Matej Polacik and Martin Reichard.

African annual fish take the adage ‘live fast, die young’ to a whole new level with the discovery that their short lifespan is accompanied by the most rapid sexual maturation of any vertebrate species. The find, reported in the open access journal EvoDevo as part of a series on extreme environments, adds to our knowledge of extremophile lifestyles.

Extreme environments can give rise to extreme adaptations. The tiny annual fish of Africa live in temporary puddles created by seasonal rainfall, and so must grow and reproduce quickly in order to lay their hardy eggs before the waters dry up.

African annual fish can grow up to 23% of their body length in a day, report Martin Reichard and colleagues, who studied wild-caught fish in captivity. One species, Nothobranchius kadleci  started reproducing at 17 days old, at a size of just 31 mm, with a related species, N. furzeri maturing only one day later. The fish then produced eggs that developed to the hatching stage in as few as 15 days, making the time from one generation to the next as little as  month – the most rapid sexual maturation time and minimum generation time of any known vertebrate species.

When the pools dry up, dormant embryos can survive in the dried mud for months, until the next rains come and the life cycle begins again. In the lab, half of embryos skipped dormancy when incubated on a peat substrate in a Petri dish. In the wild these individuals would populate secondary pools produced within a single rainy season after the primary pool desiccated. The findings suggest that rapid growth and maturation do not compromise subsequent fecundity.

Animals with a long life span can afford to take things slow. The tiny cave-dwelling salamander, olm (Proteus anguinus), which lives for over 100 years, takes 16 years to reach sexual maturity. But when the risk of mortality is high or lifespan shorter, animals reach sexual maturity earlier. The tiny goby, Schindleria, and females of house mouse lab strains (Mus musculus) become sexually mature at just 23 days old.

Earlier studies of a laboratory strain of an African annual fish suggested that it took the fish four weeks to mature, but this may have been an over-estimate. Previous reports of early maturation were based on anecdotal evidence, but this study is based on quantitative data and demonstrates that the rapid growth rate in the lab is still an underestimate compared to that in the wild.

Source: BioMed Central

Posted September 6th, 2013.

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Siblings Wired Differently

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Much as human siblings can have vastly different personalities despite their similar resemblance and genetics, two closely related species of electric fish from the Amazon produce very different electric signals. These species, new to science, are described in the open access journal ZooKeys by Drs. John Sullivan of Cornell University in Ithaca, New York, Jansen Zuanon of theNational Amazonian Research Institute in Manaus, Brazil and Cristina Cox Fernandes of the University of Massachusetts, Amherst.

The two new species are bluntnose knifefish, genus Brachyhypopomus, that live under rafts of unrooted grasses and water hyacinth along the margins of the Amazon River called “floating meadows.” These are weakly electric relatives of South America’s famous electric “eel” (not a true eel) that can produce strong electric discharges of hundreds of volts. By contrast, these weakly fishes produce pulses of only a few hundred millivolts from an organ under the body that extends out onto a filamentous tail. Nearby objects in the water create distortions to the electric field that are sensed by receptor cells on the fishes’ skin. In this way, they are able to “electrolocate” through their complex aquatic environment at night. Their short electric pulses, too weak to be sensed by touch, are also used to communicate the sender’s species identity and gender to other electric fishes.

“The most striking differences between these two similar species have to do with their electric organs and their electric organ discharges, or EODs,” says lead author John Sullivan, Curatorial Affiliate at theCornell University Museum of Vertebrates. “If it weren’t for these traits, we undoubtedly would have thought they were a single species. The one we are calling Brachyhypopomus bennetti has a huge electric organ, a short, fat tail, and produces a monophasic EOD; the other one that we’re calling Brachyhypopomus walteri has a more typical electric organ, a long thin tail, and a more typical biphasic EOD.”

It turns out the monophasic EOD of the new species Brachyhypopomus bennetti is highly unusual. Most species of this kind of knifefish produce EOD waveforms with both a positive and negative phase to them, as viewed on an oscilloscope: essentially alternating current. In this way, there is no net positive or negative current generated by the signal. “All of this fish’s relatives, including its newly described sister species, have biphasic EODs,” says Sullivan. “For that reason we know that this trait evolved in this species’ lineage. The interesting question is why.”

One widely accepted idea is that the biphasic EOD with its reduced amount of direct current (DC) is an adaptation to hide from predatory fish, like catfishes and electric eels, that are equipped with a type of electroreceptor that are sensitive to DC. So why would one species seemingly court danger by evolving a monophasic EOD?

The only other electric fish in the Amazon with a similar monophasic EOD is the fearsome electric eel. This fish has both a weak EOD used for electrolocation and communication as well as a much more powerful EOD used to stun prey and for defense. A theory proposed by Dr. Philip Stoddard of Florida International University contends that, in much the same way that the Viceroy butterfly—a species tasty to birds—evolved wing color patterns to mimic the distasteful Monarch butterfly, the harmless B. bennetti ‘s EOD waveform evolved to mimic that of the electric eel, a species electroreceptive predatory fishes may have learned to avoid.

In this paper, the authors suggest an additional possible benefit of of B. bennetti’s monophasic EOD. Unlike biphasic species, B. bennetti’s EOD waveform is largely unaffected after their tails are partially bitten off by predators, a common type of injury in this species. They suggest that this species’ preference for floating meadow habitat near river channels may put them at particularly high risk of predation and ‘tail grazing’ by other fishes.

The authors show that the EOD waveforms of Brachyhypopomus species with biphasic EODs are severely altered after such injuries, whereas those of B. bennetti are not. “Any change to the EOD waveform likely impairs electroreception and communication and the monophasic EOD waveform may have been favored by natural selection in a species that suffers a lot of tail injuries,” says Sullivan. “Selection for both EOD stability and mimicry of electric eels could be going on simultaneously…both hypotheses make predictions that should be tested,” said Sullivan.

Source: Pensoft Publishers

Posted September 4th, 2013.

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