Lizard Hunting Styles Impact Ability To Walk, Run

Source:

http://www.sciencedaily.com/releases/2008/04/080421145204.htm

ScienceDaily (Apr. 26, 2008) — The technique lizards use to grab their grub influences how they move, according to researchers at Ohio University.

A research team led by doctoral student Eric McElroy tracked 18 different species of lizards as they walked or ran in order to understand how their foraging styles impact their biomechanics.
Lizards use two basic foraging techniques. In the first approach, aptly dubbed sit-and-wait, lizards spend most of their time perched in one location waiting for their prey to pass. Then, with a quick burst of speed, they run after their prey, snatching it up with their tongues.
In the other form of foraging, known as wide or active foraging, lizards move constantly but very slowly in their environment, using their chemosensory system to stalk their prey, according to the research team, which included McElroy’s adviser Stephen Reilly, professor of biological sciences, and undergraduate honors thesis student Kristin Hickey.
Although wide foraging evolved from the sit-and-wait technique, these two styles are almost opposites. Some wide foragers are on the move about 80 percent of the time while sit-and-wait foragers may move only about 10 percent of the time, said Reilly, co-author of a recent book on the topic, Lizard Ecology, published by the Cambridge University Press.
While all lizards have the ability to run, a predatory defense mechanism, the study found that sit-and-wait lizards won’t walk. Lizards that use the sit-and-wait method of foraging use running mechanics even when moving at slower speeds.
Wide foragers, however, evolved a walking gait and mechanics. They must move at slower speeds in order to use their advanced chemosensory system to locate their prey.
Foraging and locomotion are so closely linked, in fact, that three groups of wide foragers that had reverted to using the sit-and-wait technique actually lost the ability to walk, the researchers reported.
“The most interesting aspect of this research is that it demonstrates a clear link between animal behavior and functional morphology. It’s quite amazing and surprising that the behavioral diversity that everyone knows about and is inspired by is grounded in form, function and physiology,” McElroy said.
The researchers used a race track with a built-in force plate to record the forces generated by the lizards and a high-speed video camera to record each critter moving at various speeds. The scientists collected data from the force plate and analyzed the video to determine whether the lizard was using running or walking mechanics.
The study used a large, representative sample of lizards made up of 18 different species, such as skinks, iguanas and monitor lizards. This extensive study uses one of the largest data sets for center of mass mechanics, McElroy said, and is one of the few that focuses on reptiles instead of mammals.
“Everybody works with people, dogs or horses. But they’re all freaks,” Reilly said. “They’ve gone erect, they have extra joints. They are the kings of bouncing vaulting and running fast. We are working on the sprawlers.”
The study, funded by the National Science Foundation, was featured in the April 1 edition of the Journal of Experimental Biology.
Adapted from materials provided by Ohio University.

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Arctic Marine Mammals On Thin Ice

Source:

http://www.sciencedaily.com/releases/2008/04/080423154558.htm

ScienceDaily (Apr. 26, 2008) — The loss of sea ice due to climate change could spell disaster for polar bears and other Arctic marine mammals. Sea ice is the common habitat feature uniting these unique and diverse Arctic inhabitants. Sea ice serves as a platform for resting and reproduction, influences the distribution of food sources, and provides a refuge from predators.

The loss of sea ice poses a particularly severe threat to Arctic species, such as the hooded seal, whose natural history is closely tied to, and depends on, sea ice.

The Arctic undergoes dramatic seasonal transformation. Arctic marine mammals appear to be well adapted to the extremes and variability of this environment, having survived past periods of extended warming and cooling.
"However, the rate and scale of current climate change are expected to distinguish current circumstances from those of the past several millennia. These new conditions present unique challenges to the well-being of Arctic marine mammals," says Sue Moore (NOAA/Alaska Fisheries Science Center).
The April Special Issue of Ecological Applications examines such potential effects, puts them in historical context, and describes possible conservation measures to mitigate them. The assessment reflects the latest thinking of experts representing multiple scientific disciplines.
Climate change will pose a variety of threats to marine mammals. For some, such as polar bears, it is likely to reduce the availability of their prey, requiring them to seek alternate food. Authors Bodil Bluhm and Rolf Gradinger (University of Alaska, Fairbanks) note that while some Arctic marine mammal species may be capable of adjusting to changing food availability, others may be handicapped by their very specific food requirements and hunting techniques. Species such as the walrus and polar bear fall under this category, while the beluga whale and bearded seal are among those who are more opportunistic in their eating habits and therefore potentially less vulnerable, at least in this regard.
Using a quantitative index of species sensitivity to climate change, Kristin Laidre (University of Washington) and colleagues found that the most sensitive Arctic marine mammals appear to be the hooded seal, polar bear, and the narwhal, primarily due to their reliance on sea ice and specialized feeding.
Shifts in the prey base of Arctic marine mammals would likely lead to changes in body condition and potentially affect the immune system of marine mammals, according to Kathy Burek (Alaska Veterinary Pathology Services). She and fellow researchers point out that climate change may alter pathogen transmission and exposure to infectious diseases, possibly lowering the health of marine mammals and, in the worst case, their survival. Changing environmental conditions, including more frequent bouts of severe weather and rising air and water temperatures, also could impact the health of Arctic marine mammals.
The effects of climate change will be compounded by a host of secondary factors. The loss of ice will open the Arctic to new levels of shipping, oil and gas exploration and drilling, fishing, hunting, tourism, and coastal development. These, in turn, will add new threats to marine mammal populations, including ship strikes, contaminants, and competition for prey.
Timothy Ragen (US Marine Mammal Commission) and colleagues describe how conservation measures may be able to address the secondary effects of climate change, but that only reductions in greenhouse gas emissions can--over the long-term--conserve Arctic marine mammals and the Arctic ecosystems on which they depend.
Lead authors of the collection of papers in the Special Supplement to Ecological Applications are:
John Walsh (U. of AK, Fairbanks)--climatological understanding
C.R. Harrington (Canadian Museum of Nature)--evolutionary history of arctic marine mammals
Maribeth Murray (U. of AK, Fairbanks)--past distributions of arctic marine mammals
Gregory O'Corry-Crowe (Southwest Fisheries Science Center)--past and current distributions and behaviors
Bodil Bluhm (U. of AK, Fairbanks)--food availability and implications of climate change
Kristin Laidre (U. of WA)--sensitivity to climate-induced habitat change
Kathy Burek (Alaska Veterinary Pathology Services)--effects on Arctic marine mammal health
Grete Havelsrud (Center for International Climate & Environmental Research-Oslo)--human interactions
Vera Metcalf (Eskimo Walrus Commission, Kawerak)--walrus hunting
Sue Moore (NOAA/Alaska Fisheries Science Center)/Henry Huntington (Huntington Consulting)--resilience of Arctic marine mammals to climate change
Timothy Ragen (U.S. Marine Mammal Commission)--conservation in context of climate change
Adapted from materials provided by Ecological Society of America.

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Mercury In River Moves Into Terrestrial Food Chain Through Spiders Fed To Baby Birds

Source:

http://www.sciencedaily.com/releases/2008/04/080417175221.htm

ScienceDaily (Apr. 20, 2008) — Songbirds feeding near the contaminated South River are showing high levels of mercury, even though they aren’t eating food from the river itself, according to a paper published by William and Mary researchers in the journal Science.
Lead author Dan Cristol said his paper has wide-ranging international environmental implications. Mercury is one of the world’s most troublesome pollutants, especially in water. The South River, a major tributary of Virginia’s Shenandoah River, has been under a fish consumption advisory for years, as are some 3,000 other bodies of water in the U.S.
The paper shows high levels of mercury in birds feeding near, but not from, the South River. Cristol and his colleagues also identify the source of the pollutant—mercury-laden spiders eaten by the birds. The Science paper is one of the first, if not the first, to offer scientific documentation of the infiltration of mercury from a contaminated body of water into a purely terrestrial ecosystem.
“In bodies of water affected by mercury, it’s always been assumed that only birds or wildlife that ate fish would be in danger,” said Cristol, an associate professor in William and Mary’s Department of Biology. “But we’ve now opened up the possibility that mercury levels could be very high in the surrounding terrestrial habitat, as well. It’s not just about the fish, the people who eat the fish and the animals that eat the fish. We’ve also got to look at a strip of habitat all the way around the lake or river that is affected.”
Cristol and his co-authors, all students at the College of William and Mary, have been researching mercury impacts on birds along the South River for the past three years. The waters of the river were polluted with industrial mercury sulfate from around 1930 to 1950. He explained that mercury enters the food chain through a process called methylation, in which bacteria convert the mercury to a more potent form. The methylated mercury is passed up the food chain, becoming more concentrated in the bodies of larger animals through a phenomenon known as biomagnification.
Biomagnification of mercury in fish and fish-eating birds and other animals has been studied extensively, while little attention has been paid to the effects on animals near the river, but with no direct connection to the aquatic ecosystem. The researchers studied the food actually brought by songbird parents to their nestlings.
“The birds eat a lot of spiders. Spiders are like little tiny wolves, basically, and they’ll bioaccumulate lots of contaminants in the environment. The spiders have a lot of mercury in them and are delivering the mercury to these songbirds,” Cristol said. “The question that remains is this: How are the spiders getting their mercury?”
Cristol’s group is a part of the Institute for Integrated Bird Behavior Studies at William and Mary. Co-authors on the paper are master’s degree students Ariel E. White ’07, Rebecka L. Brasso ’07, Scott L. Friedman ’07 and Anne M. Condon ’08, along with undergraduates Rachel E. Fovargue ’09, Kelly K. Hallinger ’09 and Adrian P. Monroe ’08. Cristol and his group will continue their studies of the effect of mercury in the songbirds of the Shenandoah Valley, including an examination of the effects of the contaminant on the reproduction and lifespan of the birds.
Their paper appears in the April 18 issue of the journal Science.
Adapted from materials provided by The College of William & Mary.

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Almost Extinct Turtle Discovered Living In Wild In Northern Vietnam

Source:

http://www.sciencedaily.com/releases/2008/04/080416213653.htm

ScienceDaily (Apr. 19, 2008) — "Swinhoe's soft-shell turtle" was thought to be extinct in nature. Cleveland Metroparks Zoo has just announced the discovery of a critically endangered turtle in northern Vietnam that previously was thought to be extinct in the wild. Experts from the Zoo's Asian Turtle Program confirmed that they have identified the only known living specimen of a Swinhoe's soft-shell turtle (Rafetus swinhoei) in nature.
After three years of searching lakes and wetlands along the Red River in northern Vietnam, researchers sponsored by Cleveland Metroparks Zoo and the Cleveland Zoological Society, turned their focus to a lake just west of Hanoi, where local residents claimed to have occasionally seen the gigantic soft-shell turtle. Field biologist Nguyen Xuan Thuan, with Education for Nature in Vietnam, found and photographed the turtle as it basked on the lake's surface, allowing scientists to confirm the animal was the extremely rare Swinhoe's turtle.
This is an incredibly important discovery because the Swinhoe's turtle is one of the most critically endangered species of turtle in the world," said Doug Hendrie, the Vietnam-based coordinator of Cleveland Metroparks Zoo's Asian Turtle Program. "This species has legendary status among the people of Vietnam, so this is perhaps an opportunity for the legend to live on."
Other than the turtle discovered by Cleveland Metroparks Zoo's Asian Turtle Program, only three of the giant turtles are known to remain. Two of them are at zoos in China, and one is in the Hoan Kiem Lake in Hanoi. The Swinhoe's soft-shell turtle is considered by many in Vietnam to be a national treasure.
According to folklore, the rare turtle has emerged at key points in Vietnam's history. The legend says that in the 15th century, the giant turtle rose from Hoan Kiem Lake to reclaim a magical sword that was given to Emperor Le Loi to expel the Chinese army from Vietnam. Some people believe that the single, large soft-shell turtle that occupies the lake today is the very same turtle that retrieved the sword from the Emperor and returned it to God.
Hanoi residents often line the banks of Hoan Kiem Lake in hopes of spotting the legendary turtle, which some believe brings good fortune to those who see it.
"This is one of those mythical species that people always talked about but no one ever saw, so it's hugely significant that we found this lone turtle in the wild," said Geoff Hall, General Curator of Cleveland Metroparks Zoo. "It gives us some hope for a species that truly is on the verge of extinction."
The demise of this revered species is largely due to hunters who captured and killed them for food or to make traditional medicine from their bones. Loss of nesting habitats along major rivers and pollution also are to blame. And while the recent discovery of another specimen of the Swinhoe's turtle is promising, the future of the species remains uncertain.
"Our hopes are set on finding other turtles that have somehow been overlooked by hunters or were preserved in lakes and wetlands along the Red River," Hendrie said. "However, without evidence of reproduction, the future of the legendary Hoan Kiem turtle and its three surviving cohorts looks bleak."
Efforts are underway to unite the male and female soft-shell turtles at the two separate Chinese zoos in hopes they may reproduce and ensure another generation of the species.
The largest freshwater turtle in the world, the Swinhoe's soft-shell turtle also is referred to as the Shanghai soft-shell turtle or the Yangtze soft-shell turtle. The giant turtles can weigh up to 300 pounds and measure up to 3_ feet with some living to more than 100 years old. The species historically could be found in the Red River basin of northern Vietnam, extending north into southern China and along the Yangtze River in eastern China.
Before announcing their big discovery, the team of Zoo-supported researchers notified senior government officials and took measures to protect the turtle in its natural habitat. The Swinhoe's turtle remains in the lake where it was found.
The Asian Turtle Program is a special conservation program of Cleveland Metroparks Zoo and the Cleveland Zoological Society, with all work in Vietnam being carried out in partnership with Education for Nature -- Vietnam (ENV). Additional funding and support for the Asian Turtle Program comes from Conservation International, the Turtle Survival Alliance, the Wildlife Conservation Society, Melbourne Zoo, the Turtle Conservation Fund, the Wade Foundation and the Bachelor Foundation.
Cleveland Metroparks Zoo is home to 3,000 animals representing 600 species from six continents. Committed to improving the future for wildlife, the Zoo runs conservation initiatives both locally and abroad, supporting field scientists and conservation efforts in Asia, Latin America and Africa.
Adapted from materials provided by Cleveland Metroparks Zoo.

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Early Exposure To Common Weed Killer Impairs Amphibian Development

Source:

http://www.sciencedaily.com/releases/2008/04/080416091015.htm

ScienceDaily (Apr. 18, 2008) — Tadpoles develop deformed hearts and impaired kidneys and digestive systems when exposed to the widely used herbicide atrazine in their early stages of life, according to research by Tufts University biologists.

The results present a more comprehensive picture of how this common weed killer -- once thought to be harmless to animals -- disrupts growth of vital organs in amphibians during multiple growth periods.
In recent years, worldwide amphibian population declines have fueled concerns over the potentially harmful effects of pesticides on "sentinel" organisms. Previous research had revealed negative effects of atrazine on amphibians extremely early and late in development. The Tufts study, published in the February 2008 edition of "Environmental Health Perspectives," examined tadpoles during an often overlooked period of development, organ morphogenesis.
Study Results Broadens Knowledge of Herbicide's Effects During a Vulnerable Stage
Organ morphogenesis is a brief, extremely sensitive phase in the tadpoles' growth cycle when they are starting to develop organs, noted Kelly A. McLaughlin, Associate Professor of Biology and lead researcher in the study. She explained that experiments were designed to broaden the understanding of how chemicals affect biological growth in amphibians over multiple stages of development. A $5,000 Tufts University Faculty Research Marshall Grant helped fund the study.
"Amphibians are very vulnerable to contamination since atrazine is used in the same environs where they live and breed," McLaughlin said.
Atrazine is used to control broadleaf and grassy weeds on golf courses and residential lawns, according to the Federal Environmental Protection Agency. Farmers use it to treat corn and soybeans. Atrazine blocks photosynthesis once it is absorbed by plants. Chronic exposure to the herbicide during metamorphosis altered amphibian gonadal development, according to previous research.
To study the consequences of atrazine exposure during organ morphogenesis, McLaughlin and her colleagues, Professor of Biology J. Michael Reed, doctoral candidate Jenny R. Lenkowski and Lisa Deininger, a Summer Scholars program undergraduate student, collected eggs from adult female frogs and then fertilized them in vitro. Scientists exposed the developing tadpoles to 10, 25 and 35 mg/L of atrazine. The 35 mg/L dosage simulated the average amount of herbicide used when it is applied in the field, said McLaughlin.
Multiple Impacts
Twelve to 24 hours after exposure to atrazine, tadpoles were examined for abnormal heart growth, visceral hemorrhaging, intestinal coiling, edema and apoptosis (normal cell death that is "programmed" by the body).
Compared with control populations, the tadpoles that were exposed to atrazine had a dramatically higher incidence of abnormalities. The degree of deformities generally corresponded to the size of the dose. After 48 hours of exposure, the point at which organ development is disrupted most profoundly, 57 percent of the tadpoles exposed to 35 mg/L of atrazine had hearts that were smaller than normal, compared with 2% to 3% for the two control groups.
Ectopic Cell Death
The Tufts scientists also examined atrazine exposed tadpoles for increased incidence of apoptosis by measuring levels of active caspase-3 in the pronephric kidney and midbrain. Caspase-3 is a protein needed for apoptosis to occur. They conducted measurements after 6, 12, 24 and 48 hours of exposure in tadpoles exposed to 25 and 35 mg/l of atrazine. Researchers observed that the atrazine-exposed tadpoles showed significant increases in caspase-3 levels in the kidney and midbrain at 12 hours and beyond when compared with controls. The findings indicated a high incidence of ectopic, or abnormal, apoptosis.
"The increased levels of apoptosis in the midbrain and pronephric kidney we observe suggest that atrazine may cause tissue malformation by inducing ectopic programmed cell death, either directly or indirectly through a mechanism that has not been identified," wrote the researchers.
McLaughlin and her team hope that their findings will lay a foundation for further research to determine the underlying mechanism by which atrazine exposure can affect so many different organ systems during the same stage of early development.
"Our work here documents that atrazine affects amphibian's early development, so the second question is how is this happening?" she said. "We know it blocks photosynthesis in plants but why does it have such negative impact on amphibians?"
Adapted from materials provided by Tufts University, via EurekAlert!, a service of AAAS.

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Hawaiian Plant, Thought To Be Newcomer, Actually Shaped Ecology Of The Islands From The Beginning

Source:

http://www.sciencedaily.com/releases/2008/04/080415210623.htm

ScienceDaily (Apr. 18, 2008) — Scientists at the Smithsonian Institution have discovered data that suggests one of Hawaii's most dominant plants, Metrosideros, has been a resident of the islands far longer than previously believed.

Metrosideros, commonly called "ohi'a" in the Hawaiian Islands, has puzzled researchers for years. Although previously thought to be a newcomer to the islands, these plants are well integrated into the islands' ecosystems.
However, scientists from the Smithsonian's National Museum of Natural History and the Smithsonian's National Zoo now are able to show, through molecular research, that Metrosideros may have colonized the islands soon after they formed. If so, these plants would have played an important role in shaping the ecology of the islands from the beginning.
The isolated Hawaiian Islands are home to many unique and endemic species of plants and animals. To know how these species came to interact with one another and form functioning ecosystems, scientists must first know how and when each species came to be on the islands. This is particularly important in the case of Metrosideros--many species of birds and insects are specialized to coexist and feed on these plants. Knowing when Metrosideros dispersed and colonized the islands also will give scientists a better understanding of how and when the fauna that rely on them evolved.
Until now, no definitive phylogeographical study (combining evolutionary history with current distribution patterns in order to understand both) has been done on ecologically dominant species in this island group.
"What we are finding," said Scott Miller, a Smithsonian scientist working on the project, "is a distinct geographical pattern that supports a hypothesis that these plants colonized the Hawaiian Islands sequentially as they formed." This could prove that Metrosideros played a far more important role in Hawaii's ecology than once thought.
Scientists at the Smithsonian will continue to research Metrosideros in Hawaii to further determine the plant's historical colonization pattern and its influence and role in the biodiversity of the islands.
Their findings are being published in the journal Proceedings of the Royal Society B in London on April 16.
Adapted from materials provided by Smithsonian, via EurekAlert!, a service of AAAS.

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Lizards Undergo Rapid Evolution After Introduction To A New Home

Source:

http://www.sciencedaily.com/releases/2008/04/080417112433.htm

ScienceDaily (Apr. 18, 2008) — In 1971, biologists moved five adult pairs of Italian wall lizards from their home island of Pod Kopiste, in the South Adriatic Sea, to the neighboring island of Pod Mrcaru. Now, an international team of researchers has shown that introducing these small, green-backed lizards, Podarcis sicula, to a new environment caused them to undergo rapid and large-scale evolutionary changes.
“Striking differences in head size and shape, increased bite strength and the development of new structures in the lizard’s digestive tracts were noted after only 36 years, which is an extremely short time scale,” says Duncan Irschick, a professor of biology at the University of Massachusetts Amherst. “These physical changes have occurred side-by-side with dramatic changes in population density and social structure.”
Researchers returned to the islands twice a year for three years, in the spring and summer of 2004, 2005 and 2006. Captured lizards were transported to a field laboratory and measured for snout-vent length, head dimensions and body mass. Tail clips taken for DNA analysis confirmed that the Pod Mrcaru lizards were genetically identical to the source population on Pod Kopiste.
Observed changes in head morphology were caused by adaptation to a different food source. According to Irschick, lizards on the barren island of Pod Kopiste were well-suited to catching mobile prey, feasting mainly on insects. Life on Pod Mrcaru, where they had never lived before, offered them an abundant supply of plant foods, including the leaves and stems from native shrubs. Analysis of the stomach contents of lizards on Pod Mrcaru showed that their diet included up to two-thirds plants, depending on the season, a large increase over the population of Pod Kopiste.
“As a result, individuals on Pod Mrcaru have heads that are longer, wider and taller than those on Pod Kopiste, which translates into a big increase in bite force,” says Irschick. “Because plants are tough and fibrous, high bite forces allow the lizards to crop smaller pieces from plants, which can help them break down the indigestible cell walls.”
Examination of the lizard’s digestive tracts revealed something even more surprising. Eating more plants caused the development of new structures called cecal valves, designed to slow the passage of food by creating fermentation chambers in the gut, where microbes can break down the difficult to digest portion of plants. Cecal valves, which were found in hatchlings, juveniles and adults on Pod Mrcaru, have never been reported for this species, including the source population on Pod Kopiste.
“These structures actually occur in less than 1 percent of all known species of scaled reptiles,” says Irschick. “Our data shows that evolution of novel structures can occur on extremely short time scales. Cecal valve evolution probably went hand-in-hand with a novel association between the lizards on Pod Mrcaru and microorganisms called nematodes that break down cellulose, which were found in their hindguts.”
Change in diet also affected the population density and social structure of the Pod Mrcaru population. Because plants provide a larger and more predictable food supply, there were more lizards in a given area on Pod Mrcaru. Food was obtained through browsing rather than the active pursuit of prey, and the lizards had given up defending territories.
“What is unique about this finding is that rapid evolution can affect not only the structure and function of a species, but also influence behavioral ecology and natural history,” says Irschick.
Results of the study were published March 25 in Proceedings of the National Academy of Sciences. This research was supported by the National Science Foundation and the Fund for Scientific Research in Flanders. Additional members of the research team include Anthony Herrel of Harvard University and the University of Antwerp, Kathleen Huyghe, Bieke Vanhooydonck, Thierry Backeljau and Raoul Van Damme of the University of Antwerp, Karin Breugelmans of the Royal Belgian Institute of Natural Sciences and Irena Grbac of the Croatian Natural History Museum.
Adapted from materials provided by University Of Massachusetts, Amherst.

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