Navigation Links
New study points to agriculture in frog sexual abnormalities
Date:7/3/2008

GAINESVILLE, Fla. --- A farm irrigation canal would seem a healthier place for toads than a ditch by a supermarket parking lot.

But University of Florida scientists have found the opposite is true. In a study with wide implications for a longstanding debate over whether agricultural chemicals pose a threat to amphibians, UF zoologists have found that toads in suburban areas are less likely to suffer from reproductive system abnormalities than toads near farms where some had both testes and ovaries.

"As you increase agriculture," said Lou Guillette, a distinguished professor of zoology, "you have an increasing number of abnormalities."

Guillette is one of several UF authors of a paper on the research appearing in the online version of the journal Environmental Health Perspectives. The lead author is Krista McCoy, who did the work as part of her UF School of Natural Resources and the Environment dissertation.

Several past studies have suggested a link between herbicides commonly used in farming and sexual abnormalities in tadpoles and frogs. Such deformities may be responsible for declines in frogs documented in areas affected by agricultural contaminants, such as Sierra Nevada, Calif., McCoy said. Amphibians are declining worldwide and agricultural chemicals are considered to be one likely cause, she said. Others include pathogenic infections and habitat loss.

Past research has compared frogs collected from natural areas with those collected from agricultural areas. Other efforts have pointed to specific chemicals, including the herbicide Atrazine, as causing abnormalities. The UF study is the first peer-reviewed study to compare abnormalities in wild toads toads are a variety of frogs -- from heavily farmed areas with frogs from both partially farmed and completely suburban areas. In so doing, it highlights the difference between the impact of agriculture versus development.

"Our study is the first to explicitly ask, of these two areas of human disturbance, do we see a greater proportion of abnormal animals in one versus another?" Guillette said.

Because the results implicate agriculture, future research can narrow the focus to agricultural chemicals, McCoy said.

"Because we know what chemicals are used at these agricultural sites, we can begin to pin down the chemical cause of these abnormalities by conducting controlled experiments with each chemical alone and in combination," she said.

The researchers gathered giant toads, known scientifically as Bufo marinus, from five sites stretching from Lake Worth to Belle Glade and down to Homestead in South Florida. Bufo marinus is a very large, exotic, invasive, species known to be deadly to small animals. Guillette said the researchers studied the toad in part because they are easy to catch and their large size ensures enough blood for analysis. Also, he said, "they are common in other agricultural areas around the world," which means they are a good generalist species.

One of the sites consisted almost entirely of land devoted to sugar cane or vegetable farms. The amount of farmland declined in three other sites, with the last being entirely suburban. Researchers calculated the amount of farmland in each site using Google Earth images.

Each site was 2.1 square miles, with the toads collected at the center. That's because the toad's home range is known to be about 1.2 miles, and the researchers sought only those toads living entirely within each site. The researchers collected at least 20 toads from each site in 2005 and 2006.

Examination of the euthanized toads revealed a pattern: The more agricultural the land where they lived, the more sexual organ abnormalities or so-called "intersex" toads -- toads who have both female and male internal reproductive organs, not a normal condition for this and most species of amphibians.

While normal male toads' forelimbs are thicker and stronger than those of their female counterparts, more of the intersex frogs only found in agricultural areas had thin, weak forearms. Also, intersexes had fewer "nuptial pads," areas of scrappy skin on their feet used to grip females during copulation.

Where a sex was clear, the male toads appeared by far the most affected. Normal males are brown, while females are mottled with brown stripes. However, males from agricultural areas were mottled, looking like females.

Internally, the more agricultural the sites, the more feminized the males' reproductive organs. Many had both ovaries and testes. Not only that, both the impacted males and the intersex frogs had less of the male hormone testosterone than normal males, suggesting diminished reproductive capabilities, Guillette said.

Guillette and McCoy said the study's results may have important implications not only for other wild species, but also for people.

"What we are finding in Bufo marinus might also occur in other animals, including other amphibian species and humans," McCoy said. "In fact, reproductive abnormalities are increasing in humans and these increases could partially be due to exposure to pesticides."


'/>"/>

Contact: Lou Guillette
ljg@zoo.ufl.edu
University of Florida
Source:Eurekalert

Related biology news :

1. Childhood obesity indicates greater risk of school absenteeism, Penn study reveals
2. A study by the MUHC and McGill University opens a new door to understanding cancer
3. Study begins to reveal clues to the cause and progression of sepsis
4. Clones on task serve greater good, evolutionary study shows
5. New study warns limited carbon market puts 20 percent of tropical forest at risk
6. New study examines how rearing environment can alter navigation
7. Study links cat disease to flame retardants in furniture and to pet food
8. New continent and species discovered in Atlantic study
9. Study shows link between alcohol consumption and hiv disease progression
10. Feeling hot, hot, hot: New study suggests ways to control fever-induced seizures
11. Study finds environmental tests help predict hospital-acquired Legionnaires disease risk
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/2/2017)... , Feb. 1, 2017  Central to its ... meaningful advances worldwide, The Japan Prize Foundation today ... who have pushed the envelope in their respective ... Communication. Three scientists are being recognized with the ... that not only contribute to the advancement of ...
(Date:1/31/2017)... , Jan. 31, 2017  Spero Therapeutics, LLC, ... for the treatment of bacterial infections, today announced ... antibacterial candidates from Pro Bono Bio Ltd (PBB) ... of multi-drug resistant forms of Gram-negative bacteria.   The ... Infectives Ltd, a PBB group company. ...
(Date:1/26/2017)... -- Crossmatch, a leading provider of security and identity management ... fraud, waste and abuse in assistance operations around the ... Disaster Relief conference in Panama City ... foreign assistance organizations throughout Latin America ... largely unacknowledged problem in the foreign assistance and disaster ...
Breaking Biology News(10 mins):
(Date:2/16/2017)... 16, 2017  ImMAGE Biotherapeutics (OTCMKTS: IMMG), an early-stage biotechnology ... a better treatment for triple negative breast cancer (TNBC), announced ... France program. The YEi Start in ... to help entrepreneurs grow their business in France ... American companies selected to complete an intensive one week immersion ...
(Date:2/16/2017)... 16, 2017 Research and Markets ... Global Markets" report to their offering. ... ... biobrick parts, delivery plasmids, chassis organisms, synthetic cells, production ... genome editing, bioinformatics and specialty media) and enabled technologies ...
(Date:2/16/2017)... DENVER , Feb. 16, 2017 UCHealth ... hospital to utilize LungDirect for pulmonary nodule patient management. ... a nodule, or a spot on the lung, UCHealth ... spent on manual data entry. Stephanie ... been tracking my nodule patients with an Excel spreadsheet, ...
(Date:2/16/2017)... 2017  Windtree Therapeutics, Inc. (Nasdaq: ... aerosolized KL4 surfactant therapies for respiratory diseases, announced ... showed that aerosolized KL4 surfactant reduced lung inflammation ... animal model. The Company believes that these preclinical ... that supports the role of KL4 surfactant as ...
Breaking Biology Technology: