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Pesticide Atrazine Can Turn Male Frogs Into Females

University of California – Berkeley

Atrazine, one of the world’s most widely used pesticides, emasculates three-quarters of adult male frogs, who then cannot reproduce, and turns one in 10 into females, according to a new study by University of California, Berkeley, biologists. While the experiments were performed on a common laboratory frog, the African clawed frog, field studies indicate that atrazine, a potent endocrine disruptor, similarly affects frogs in the wild, and could possibly be one of the causes of amphibian declines around the globe.

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Tasmanian Devils

Australian scientist, Kathy Belov, discovered a genetically distinct colony of Tasmanian devils that may save the species from being extinct from a contagious cancer.

“We think these devils may be able to see the cancer cells as foreign and mount an immune response against them,” Ms. Belov said. “We think more animals might survive in the wild than we initially thought.”

“I don’t think this means that we can sit back and go, ‘Everything is OK,’ because we’ve already seen that the tumor has started to evolve,” Belov warned. “But now we can say that we’ve got a glimmer of hope. There may be some animals that may survive this epidemic.”

Tasmanian devils with large facial tumours were photographed in north-east Tasmania during 1996. More than a decade later, we know these characteristics are consistent with Devil Facial Tumour Disease (DFTD) – a fatal condition in Tasmanian devils, characterised by cancers around the mouth and head.

As at February 2010, the Tasmanian devil population has decreased by approximately 80%. DFTD has been recorded across more than 60% of the state, spreading between seven to 20km easterly per year (depending on the habitat). To date, there has not been any evidence of DFTD found in the far north-west of Tasmania.

The Save the Tasmanian Devil Program is the official joint strategy of the Australian and Tasmanian Governments. It features:

•Captive and free-ranging Insurance Populations
•Collaborative laboratory-based investigations of DFTD
•Management strategies for wild populations.
See the Save the Tasmanian Devil Program information on the Tasmanian Department of Primary Industries, Parks, Water and Environment website.

What we know about the disease
The Tasmanian devil disease is a new disease, an infectious cancer, that is restricted to Tasmanian devils.

No affected animals were reported among the 2000-plus Tasmanian devils trapped by wildlife biologists between 1964 and 1995.

Once the cancer becomes visible, it always appears to be fatal – usually within three months. Small lesions, or lumps, in and around the mouth quickly develop into large tumours on the face and neck (and sometimes other parts of the body).

Tasmanian devils with facial tumours find it difficult to eat. Death results from starvation and the breakdown of body functions.

In diseased areas, nearly all the Tasmanian devils that are sexually mature (older than two years of age) become infected and succumb to the disease. Juveniles as young as one year old can also be infected.

Devil listed as “endangered”
In May 2009, the Australian Government uplisted the Tasmanian devil from “Vulnerable” to “Endangered” under national environmental law.

Tasmania’s Threatened Species Act 1995 has also listed the devil as “Endangered” since May 2008. Federal Environment Minister, Peter Garrett, said the species was under continued threat, but that the uplisting would provide it with greater protection.

“Fortunately, strong action is being taken to find out more about the Devil Facial Tumour Disease and to stop its spread,” Mr Garrett said.

“The Australian Government has already committed $10 million over five years to the Save the Tasmanian Devil Program. This is to help with research into disease transmission and treatment, and to support captive and wild populations.”

Sightings of the devil have declined by 80% since before 1996, when DFTD was first observed. As at February 2010, DFTD has been found across more than 60% of Tasmania. No cases of DFTD have been recorded west of the Murchison Highway, which roughly runs between Burnie and Queenstown.

In September 2006, DFTD was gazetted under the Animal Health Act 1995 as a List B notifiable disease. The Tasmanian devil has also been listed as “Endangered” on the Red List of the International Union for the Conservation of Nature and Natural Resources (IUCN) – widely considered the most authoritative and objective system for classifying species in terms of their risk of extinction.

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The potentially deadly yellow-fever-transmitting Aedes aegypti mosquito detects the specific chemical structure of a compound called octenol as one way to find a mammalian host for a blood meal, Agricultural Research Service (ARS) scientists report.

Scientists have long known that mosquitoes can detect octenol, but this most recent finding by ARS entomologists Joseph Dickens and Jonathan Bohbot explains in greater detail how Ae. aegypti—and possibly other mosquito species—accomplish this.

Dickens and Bohbot, at the ARS Invasive Insect Biocontrol and Behavior Laboratory in Beltsville, Md., have shown that Ae. aegypti taps into the “right-handed” and “left-handed” structural nature of octenol, which is emitted by people, cattle and other mammals. This ability to detect the “handedness” of molecules has been shown in mammals, but the discovery is the first case of scientists finding out how it works in an insect, according to the researchers.

When they hunt for a blood meal, mosquitoes hone in on a variety of chemicals, including carbon dioxide, lactic acid, ammonia and octenol. Octenol is one of many carbon-based compounds that have a molecular structure that can take on either a “right-handed” or “left-handed” form. Each form is a mirror image of the other, and a form’s “handedness” is determined by how its molecular bonds are assembled.

The scientists used frog eggs to help them make their discovery. They injected RNA from Ae. aegypti into the frog eggs, allowing the egg membranes to mimic the mosquito’s ability to detect octenol. Then they attached microelectrodes to the frog egg cell membranes, passed octenol over them and recorded the electrical signals stimulated by the odors.

They ran the tests using both the right- and left-handed forms of octenol. The scientists found heightened electrical activity when the membrane was exposed to the right-handed form, and weakened activity when it was exposed to the left-handed form.

There are many natural compounds that can take on either a right-handed or left-handed form. While the effects of those differences on many plants and animals remains a mystery, the report, published in PLoS ONE, shows the effects of octenol’s dual structure on the yellow fever mosquito and adds to scientists’ understanding of how mosquitoes sense the world around them. It also may open the door to speedier development of better mosquito repellents and traps, according to Dickens.

The team’s research is being funded by the Department of Defense Deployed War Fighter Protection Research Program.

ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture.

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