Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Biologists discover amphibian eggs use defenses against water molds

23.10.2006
Protective jelly layers and hatching early help embryos avoid dangerous molds

Boston University (BU) scientists have discovered that several species of amphibians use defense mechanisms to protect themselves against deadly water molds found in vernal pools of New England. Using both field observations and laboratory experiments, Ivan Gomez-Mestre, a research associate in Professor Karen Warkentin's laboratory in the Department of Biology at BU, describes the various methods used by the spotted salamander, wood frog, and American toad to help avoid and survive water mold infections. The results appear in the October issue of the journal Ecology.

"Certain water molds cause substantial mortality for aquatic eggs of a wide range of fish and amphibian species throughout the world," said Dr. Gomez-Mestre. "The observations and results of this study demonstrate that there are both parental and embryonic-stage traits that defend egg clusters against water mold infections in three species of amphibians found in the Northeast."

In the Northeast, vernal pools fill with the rising water table of fall and winter or with the melting and runoff of winter and spring snow and rain. Many vernal pools in the region are covered with ice in the winter months and contain water during spring and early summer. Typically by late summer, most pools are completely dry.

To assess the incidence and impact of water mold on eggs of the three study species, Gomez-Mestre and the team – which included Dr. Warkentin and Justin Touchon, a graduate student in the Warkentin lab – surveyed nine vernal pools in Lynn Woods Reservation (Lynn, MA) in spring 2005. The team surveyed the ponds twice weekly from late-March through early-June before the pools dried for the summer. All egg clutches found were flagged and monitored until they hatched except for several that were collected for laboratory experiments.

In order to determine the presence or absence of water molds in the ponds, the researchers sank five tea bags filled with sterilized hemp seeds into each pond as water mold baits. After 10 days, the bags were retrieved and plated on a sterilized cornmeal agar medium on Petri dishes and grown in incubators. Water mold was found in all ponds surveyed. Eight of the nine had high infection rates, with 66 – 86 percent of baits infected, but baits from the largest pond with the thickest tree canopy and the lowest temperature showed only 16 percent infection rate.

"We visually estimated the degree of mold infection within each clutch and considered clutches to be infected when mold had grown over 5 percent or more of the clutch and increased over subsequent observations," said Touchon.

According to the results, all three amphibian species display behaviors that help protect them from or survive infections by water molds. These defense mechanisms are carried out either by the adult females when laying eggs or by the developing embryos themselves.

Spotted salamanders wrap their eggs in a protective jelly layer that prevents mold from reaching the embryos. Wood frog egg clusters have less jelly, but are laid while ponds are still cold and mold growth is slow. Eggs of the American toad experience the highest mold infection levels since they are surrounded by only a thin jelly coating and laid when ponds have warmed and mold grows rapidly. However, eggs of all three species are capable of hatching early if mold reaches them and this response was strongest in the American toads. Toad embryos hatched as much as 36 percent prematurely, before they could even move, suggesting accelerated development and the use of enzymes to aid hatching.

"This is quite a dramatic change. If you compared it to humans, this would be like a six months premature baby," said Warkentin.

In the case of the salamanders, early hatching occurred only after the protective jelly coating was removed in the lab and mold was able to reach the eggs. Although this jelly works well as an anti-mold defense for spotted salamanders near Boston, in upstate New York the species suffers high mortality from water mold infections.

"We don't yet know if the mold is different in Boston, or the eggs," said Gomez-Mestre.

Another interesting finding from the study is despite being potential toad hatchling predators, wood frog tadpoles can have a positive effect on toad eggs by eating mold off infected toad clutches which increases their survival rates.

Water molds are a common threat for aquatic embryos, but the study species all demonstrated traits that function to reduce the risk of infection, as well as responses once infection occurs. Parental traits, including breeding early in the year or providing eggs with a protective jelly, decrease the risk of infection to a clutch while hatching early enables embryos to escape a clutch already infected with mold.

"These defenses appear to reduce the overall impact of water mold, so that massive egg mortality is normally associated with a several stressors. Furthermore, interactions with other species may further reduce mortality rates of infected clutches," explained Gomez-Mestre. "The impact of water molds on a given species therefore depends not only on the effectiveness of the its own defenses, but also on the community composition and the ecological interactions at work in the pool."

Kira Edler | EurekAlert!
Further information:
http://www.bu.edu

More articles from Ecology, The Environment and Conservation:

nachricht Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>