Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists hone in on causes of amphibian deformities

15.01.2003


A dramatic increase in deformed frogs and other amphibians is being caused by a range of environmental factors, all of which ultimately can be linked to human impacts on habitat, but the primary cause of many of the deformities is an epidemic of a key parasite.



These findings are the results of eight years of research by scientists around the world, and are presented in the February issue of Scientific American by researchers from Oregon State University and the University of Wisconsin.

The cause of a disturbing increase in amphibians with deformities are explored in a new article in Scientific American by researchers from Oregon State University and the University of Wisconsin. Extra legs, such as those found on the frogs in these images, are one of the most common deformities.
Click on image to go to downloadable photo



Increases in ultraviolet radiation, contaminated water and a parasitic trematode are the leading culprits in the wave of deformed legs, eye damage and other ailments that have now been found in more than 60 species of frogs, toads and salamanders in 46 states and across four continents. Of these three leading causes, the parasite appears to be the major cause of many of the deformities, the scientists say.

"We’ve finally synthesized from a wide body of research the range of causes that are linked to amphibian deformities," said Andrew Blaustein, a professor of zoology at OSU and co-author of the report with Pieter T.J. Johnson, a doctoral candidate at the University of Wisconsin.

"As is often the case in nature, it’s now clear that there are multiple causes to this problem, some of which may act in concert," Blaustein said. "But the common thread that runs through the issue is that each cause can eventually be traced to human alteration of our climate or amphibian habitat. And one of the most common deformities, extra or deformed legs, is most often linked to a particular parasite."

The deformity problem first received widespread media attention when deformed frogs were spotted by school children in Minnesota in 1995, but it quickly became apparent that its scope was extraordinarily broad and the impacts severe - in some frog populations, including one near Corvallis, Ore., 75-80 percent of the frogs are deformed.

There has always been some level of deformities in amphibians, scientists say, but nothing of this magnitude. And the sudden increase in deformities may also be one factor in overall population declines.

"Deformities undoubtedly impair amphibian survival and most likely contribute to the dramatic declines in populations that have been recognized as a global concern since 1989," the researchers said in their report. "Both trends are disturbing in their own right and are also a warning for the planet. Chances are good that factors affecting these animals harshly today are also beginning to take a toll on other species."

Since the issue first gained national attention, a range of differing causes for amphibian deformities has been suggested and studied. Years of research by dozens of investigators have now narrowed the causes down to three primary areas:

  • UVB Radiation: Rising levels of ultraviolet radiation, a side effect of the erosion of Earth’s protective ozone layer, can be implicated in at least some deformities. Research at OSU and elsewhere has shown UVB radiation can kill amphibian embryos and larvae, cause serious eye damage in adult frogs, and induce various types of bodily deformities in frogs and salamanders. It is less relevant to the range of leg deformities seen in nature, and does not lead to the growth of extra legs.

  • Water Pollution: Toxicologists studied whether widespread water pollution, especially that caused by pesticide runoff, might cause embryo deformities or other problems. Laboratory tests suggest there may be some linkage, but field tests make it clear pesticide exposure can’t be the sole cause of amphibian deformities.

  • Parasites: A tiny trematode appears to cause a significant amount of the leg deformities in amphibians, as it works through a complex ecological cycle that at various times includes aquatic snails, amphibians and birds. The parasite can form a cyst in frogs and disrupt normal limb development.

According to the researchers, the story of the parasitic trematode reveals just how complicated natural ecological processes can be, and how difficult it is to trace problems to their underlying cause. In its life cycle, the parasite at times depends on snails for survival and birds for reproduction and transportation. The amphibians, themselves, are actually just an intermediary host.

"We need to understand the complex relationships among human activity, the parasite and its hosts, and the environment in which they interact," Johnson said.

There are many interrelationships among various factors. Snails, for instance, are necessary to the life cycle of the trematode that can cause frog deformities. But snail populations may be surging at some sites due to fertilizer runoff and cattle manure that cause algal blooms and more food for the snails. A survey of the western U.S. in 2000 found that 44 of the 59 wetlands in which amphibians were infected by this parasitic trematode were reservoirs, farm ponds or other artificial bodies of water.

And water pollutants or UVB radiation, while not directly causing the majority of deformities, may set the stage by weakening an amphibian’s immune system and making it more vulnerable to a parasitic infection.

"The challenge to scientists becomes teasing apart these agents to understand their interactions," the researchers said in this article. "Humans and other animals may be affected by the same environmental insults harming amphibians. We should heed their warning."

Andrew Blaustein | EurekAlert!
Further information:
http://oregonstate.edu/dept/ncs/newsarch/2003/Jan03/explain.htm

More articles from Ecology, The Environment and Conservation:

nachricht Listening in: Acoustic monitoring devices detect illegal hunting and logging
14.12.2017 | Gesellschaft für Ökologie e.V.

nachricht How fires are changing the tundra’s face
12.12.2017 | Gesellschaft für Ökologie e.V.

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>