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 A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

nachricht Value from wastewater
16.08.2017 | Hochschule Landshut

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New bioimaging technique is fast and economical

21.08.2017 | Medical Engineering

Silk could improve sensitivity, flexibility of wearable body sensors

21.08.2017 | Materials Sciences

On the way to developing a new active ingredient against chronic infections

21.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>