Celebrating tadpole diversity

Tadpoles

The ability of certain Panamanian species to survive will depend on the ability of the rescue project to perfect specialized care for the individual species. (Photo by Lindsay Renick Mayer, Smithsonian

When we talk about frog diversity, we always mention how many species there are, or how they are found all over the world. We say how much frogs vary in size, or how colorful they can be. This is all true: there are more than 4,900 frog species, found on every continent, ranging from ½-inch long to more than a foot, that come in every color of the rainbow. It makes sense, then, that frogs are just as diverse during their other stages of the life cycle. Tadpoles, in fact, are among the most diverse vertebrates on Earth and are themselves morphologically and behaviorally unique from their adult counterparts.

Special Adaptations

Depending on the species, tadpoles can stay in the larval stage from eight days to two years, and vary in length from 1 to 4 inches. Overall, there is greater tadpole diversity in the tropics, but variations occur within habitats, as well. Even tadpoles with the same feeding habits can have diverse mouth shapes or behaviors. For example, tadpoles of the Asian horned frog (Megophrys montana) have an upturned mouth because they eat from the surface. Recently, however, scientists have observed a Honduran tadpole called Duellmanohyla soralia that also eats from the surface, but has a mouth in the more traditional spot. Instead, the Duellmanohyla soralia turns its body upside-down to reach the surface.

“We see tadpoles solving the same problems of survival in different ways,” says Dr. Roy McDiarmid, an amphibian zoologist and tadpole expert at the National Museum of Natural History. “This is where their diversity derives from.”

These variations show how tadpoles’ features are shaped largely by their surrounding environments. For example, tadpoles seem especially good at responding to strong predator presence. Over time tadpoles can grow their tails longer and deeper if there are numerous predators, allowing them to swim faster and look bigger. For European common frog (Rana temporaria) tadpoles, longer tails increase their chances of escape from predators up to 30 percent, according to the Institute of Zoology.

Like tail length, other adaptations can protect tadpoles from being eaten. While the majority of tadpole species have brown or faded coloration, several are multicolored. Contrary to its name, Cope’s gray tree frog (Hyla chrysoscelis) tadpoles grow red tails in response to the presence of dragonflies. Called aposematism, vibrant colors make these tadpoles appear larger or distasteful to their predators.

Researchers have only recently discovered other survival mechanisms that tadpoles have developed. In 2006, scientists discovered that if attacked, red-eyed tree frog (Agalychnis callidryas) embryos can hatch themselves within seconds and escape into the water below. These embryos can interpret vibrations on the water with astonishing precision.

“It turns out that when a snake bites into a gooey mass, all the embryos try to wiggle free,” Karen Warkentin, a biologist working at the Smithsonian Tropical Research Institute in Panama, told National Geographic.  “A wasp’s more focused attack prompts only neighboring eggs to hatch. And a rainstorm triggers nothing at all.”

Other recent research has looked at tadpole sensory input, such as smell and sound. In 2009, researchers at the University of California Davis determined that wood frog (Rana sylvatica) tadpoles can “smell” their primary predator, the salamander. The “odor” of a salamander in the water caused tadpoles to freeze. The strength of the scent determined how long the tadpoles remained still. In 2010, Dr. Guillermo Natale discovered the first evidence of aural larva communication. Natale heard tadpoles of the Bell’s horned frog (Ceratophrys ornate) “screaming” underwater when a threat was present.

Discovery

Tadpole

The amount of tadpole diversity rivals that of their adult life forms. (Photo by Brian Gratwicke, Smithsonian Conservation Biology Institute)

New and unpredictable tadpole discoveries continue to go on worldwide. For example, biologists at the Australian Museum in Sydney recently discovered that tadpoles of the vampire flying frog (Rhacophorus vampyrus) have small black fangs, instead of traditional mouthparts. In general, scientists estimate that more than 1,000 frog species have yet to be discovered, not to mention all the intricacies of their life stages.

Tadpoles are also essential for understanding the dramatic decline in frog populations. Chytrid, the epidemic that has affected 30 percent of the world’s amphibian population, is the lead cause of this decline. In tadpoles, chytrid only infects the keratin around their mouths. However, as they metamorphose into frogs, chytrid fatally spreads throughout their bodies. By studying tadpoles, we can better understand how frogs contract and carry chytrid.

“When frog species are disappearing like they are, you would want to know what’s going on at each stage of the life cycle, egg to larva to juvenile to adult–everything,” McDiarmid says.

The Challenges of Breeding

For the Panama Amphibian Rescue and Conservation Project, every tadpole means the chance for a species to survive. But because many of the rescue project’s priority species have never been kept or bred in captivity before, rearing tadpoles can mean a steep learning curve.

“Breeding frogs isn’t just about putting a male and female together and hoping for eggs,” said Lindsay Renick Mayer, spokesperson for the rescue project. “It’s about specialized husbandry for each individual species among a diverse array and unfortunately for some of these species we’re learning those skills even as the species dwindles down to just a few remaining individuals. Whether these species are one day returned to the wild depends on the rescue project’s success in perfecting the variety of care in a short period of time.”

Nadia Hlebowitsh, Smithsonian’s National Zoo

AZA Updates Amphibian Husbandry Guide

Amphibian Husbandry Resource Guide

The AZA has released an updated Amphibian Husbandry Resource Guide, a user-friendly source to aid in the development of successful amphibian conservation programs. With more thna 6,900 species of amphibians in the world, there is still much to be learned about their natural history and captive husbandry requirements. This lack of information and expertise can impede the urgent action needed for the 500+ threatened species in risk of disappearing within the immediate future. The zoological community and private sector have made great strides within the last two decades regarding amphibian husbandry and reproduction techniques, and will continue to develop new and innovative methods each year. However, as amphibian populations wane, it’s important to quickly and effectively pool resources, share expertise and learn from shared experiences to effectively remain ahead of the extinction tide. You can find a rich array of other resources on amphibians on the AZA website.

Cindy Hoffman, Defenders of Wildlife

New experiment may offer hope for frogs facing chytrid

Probiotics bath

The golden frogs were given a bath in one of four probiotic solutions. (Photo by Brian Gratwicke, Smithsonian Conservation Biology Institute)

We usually think of bacteria as bad for us, but that isn’t always the case. For us humans, the most common examples of helpful bacteria, or probiotics, live in yogurt. Now, scientists believe amphibian probiotics may be the key to fighting chytridiomycosis, the fungal disease devastating frogs around the world.

A few years ago, Reid Harris, a biology professor at James Madison University, discovered that local salamanders that could survive chytrid played host to bacteria in their skin. Now, Brian Gratwicke, a research biologist at the Smithsonian Conservation Biology Institute, is collaborating with a team from Virginia Tech, James Madison, Villanova and Vanderbilt Universities in an experiment to see if similar bacteria can protect the Panamanian golden frog, which he calls “the poster-child for amphibian conservation.”

The first step is to find a probiotic that will stick to the golden frogs. In early December, the team began giving golden frogs baths using four different types of bacteria. Researchers gathered the potential probiotics from frogs in Panama in 2009. The finalists were chosen based on their ability to prevent chytrid growth in lab tests, with a preference for bacteria that are common in close relatives of Panamanian golden frogs.

Every two weeks, each frog is swabbed to check whether its probiotic has made itself at home. The tests take some time, so a month and a half in, the team is still waiting for results to see which probiotics are sticking. But they do have some good news already.

“The bacteria haven’t been causing any problems with the frogs and they all look healthy,” said Gratwicke, who emphasizes how important it is to use only beneficial bacteria. In addition to tracking weight gain and other visible characteristics, Shawna Cikanek, a student at Kansas State College of Veterinary Medicine is using frog poop to study stress hormones to get a better picture of the animals’ overall health and whether the bacteria are causing any stress.

The probiotics that stick to the frogs for a full three months will move on to the next round of tests, when bacteria-shielded frogs will be infected with chytrid to check for any adverse effects.

“Hopefully, the bacteria are going to do their thing and protect these little guys,” said Matt Becker, a PhD candidate from Virginia Tech who is conducting the experiment. Whatever probiotics make the cut will be tested again on golden frogs bred in Panama before scientists develop a final plan.

So far, chytrid has defied attempts to stop it. Scientists may be able to selectively breed frogs resistant to chytrid, but there has been very little work done so far in that direction. But there are high hopes for probiotics’ potential to protect frogs. “It’s a long shot, but it’s our best shot,” said Gratwicke.

Becker hopes that one day, probiotics will allow Panamanian golden frogs to return to their homes. “These guys are really neat and it’s so sad not to see them in the wild,” he said. “We have a moral obligation since indicators are pointing to humans as major spreaders of the disease through the frog trade.”

Meghan Bartels, Smithsonian’s National Zoo

Volunteering for Save the Frogs Day

April 28 was Save the Frogs Day. (Photo courtesy of the Panama Amphibian Rescue and Conservation Project)

Volunteering for the Panama Amphibian Rescue and Conservation Project reached a whole new level of awesomeness when we organized an event for the 4th Annual Save the Frogs Day. Being able to spread the word about global amphibian declines and the status of Panama’s amphibian population was a rewarding way to spend the day at the Summit Municipal Park where the project is located. More than 200 events in 39 countries took place in this year’s Save the Frogs Day.

On April 28, we arrived at the park during the tranquility of the early morning to set up our tables and chairs amidst the chattering of the capuchin monkeys, while the parrots never tired of greeting us with their cheerful “hola.” Meanwhile in another part of the park, our star attractions were enjoying their climate-controlled habitat, as their likeness was depicted in coloring sheets for kids to learn about the importance of our endangered amphibian friends. Once the families started arriving, kids and parents alike were welcomed under our tent to color, paint, make frog masks, and get their questions answered about amphibian conservation. In the span of just a few hours, we had an impressive wall of frog art paintings hanging out to dry, which the kids took home as a reminder about saving the frogs and their environment. They will perhaps become the next generation of amphibian conservationists.

Erica Wrona, volunteer for the Panama Amphibian Rescue and Conservation Project

Now Hear This

Is your volume turned up? Hear what this horned marsupial frog (Gastrotheca cornuta) has to say to Cheyenne Mountain Zoo’s Dr. Della Garelle during an exam at an Amphibian Rescue and Conservation Project breeding center in Panama. He sounds more like a baby than a frog! This uniquely vocal species is on the verge of extinction due to the chytrid fungus.

The female horned marsupial frog carries fertilized eggs in a pouch on her back and the eggs hatch as fully developed frogs! This particular species produces the largest known amphibian eggs.

Katie Borremans, Cheyenne Mountain Zoo

Rocket frog.

Panama poison dart frog (Colostethus panamensis)

Panama poison dart frog (Colostethus panamensis)

Cute Frog of the Week: May 14, 2012

The Panama poison dart frog, also called the common rocket frog, lives in Columbia and Panama. They prefer to live in humid forested environments along rocky streams in lowland areas and are members of a poisonous family of amphibians.

Like the green poison dart frog, these guys monitor their eggs after they lay them on piles of leaves, and females carry the newly hatched tadpoles on their backs for up to nine days where they continue to grow, before eventually being released into a fast-flowing stream to complete their development. This tends to be a behavioral trend among poison dart frogs, though depending on the species, either the male or female will care for the young and move them. In addition, different species of poison dart frogs will carry their young to different kinds of water sources, whether it is a pool, lake, stream, etc.

These frogs are diurnal, meaning that they are most active during the day. Although not endangered, their numbers are decreasing, most likely due to deforestation, illegal planting, pesticides, logging and human settlement. When its habitat is altered, these frogs do not adapt well, so in order to preserve the Panama poison dart frog population, there have been some protected areas established throughout Central America.

Photo by Brian Gratwicke, Smithsonian Conservation Biology Institute.

Every week the Panama Amphibian Rescue and Conservation Project posts a new photo of a cute frog from anywhere in the world with an interesting, fun and unique story to tell. Be sure to check back every Monday for the latest addition.

Send us your own cute frogs by uploading your photos here: http://www.flickr.com/groups/cutefrogoftheweek/

Start Spreading the Word

Paul Crump

Houston Zoo Amphibian Program Manager Paul Crump meets a family attending the Milam County Nature Fest. The aquarium on the table holds Houston toad ‘ambassadors.’ More than 600 people attended the one day Nature Fest in Rockdale, Texas. (Photo courtesy of the Houston Zoo)

Learning about endangered species is the first step in helping to protect them.

In 1968, a small amphibian landed a spot on the list of “Rare and Endangered Fish and Wildlife of the United States.” Five years later, the Houston toad was included in the passing of the Endangered Species Act and became one of the first amphibian species in the United States, and maybe even the world, to be recognized as declining.

Today the Houston toad is no longer found in its namesake city, and fewer than 300 individuals remain in the wild, largely due to habitat loss.  The Houston Zoo is working with the US Fish and Wildlife Service, Texas Parks and Wildlife Department, Texas State University and the Environmental Defense Fund to ensure the toad’s survival. The Zoo also works with private landowners to restore habitat and monitor populations in Houston toad counties. But before we can involve a landowner in the project we have to find them–and that’s where the Zoo’s education and outreach programs come in.

Mainstream media of course plays a major role in the effort.  A recent front-page story in the Houston Chronicle highlighted the need for private landowners to participate in the restoration project. The article generated a dozen responses from interested landowners and raised the profile of the effort. But grassroots efforts also play an important role.

Through our collaboration with the US Fish and Wildlife Service and the Texas Parks and Wildlife Department, the Zoo has developed opportunities for the presentation of education and outreach programs in counties northwest of Houston, the Houston toad’s current range. In late February, a landowner workshop sponsored by Texas AgriLife Extension and the Texas Forest Service brought 200 landowners together to learn about woodland and pond management and how to get involved in the Houston toad recovery project. Recently, three members of the Houston Zoo Conservation Department participated in the Milam County Nature Fest 2012. Supported by the Texas Parks and Wildlife Department, the festival drew more than 600 participants from surrounding communities in prime Houston toad range for a day of nature exhibits and demonstrations, crafts and games for children and an opportunity to meet Houston toads and hear from those who are directly involved in the toad’s recovery.

It’s one thing to tell the world about the importance of amphibians to the balance of nature. It’s another thing entirely when you see the smile on a child’s face when they have an up-close encounter with an endangered species. Then you know you’ve connected.

-Brian Hill, Houston Zoo

Smithsonian scientists survey frogs in the Peruvian Andes

Acancocha water frog (Telmatobius jelskii)

Last December two researchers from the Smithsonian Conservation Biology Institute spent two weeks in Peru surveying the Acancocha water frog (Photo by Jessica Deichmann, SCBI)

Imagine measuring the tail of a squirmy, inch-long tadpole. Now imagine doing that where the air is thin enough to make you dizzy, a hail storm is about to start and you just spent 45 minutes up to your elbows in a freezing cold stream.

Last December, Jessica Deichmann, a research scientist with the Smithsonian Conservation Biology Institute, and Ed Smith, a biologist at the Smithsonian’s National Zoo’s Amazonia Exhibit, spent two weeks doing just that to complete a survey of the Acancocha water frog (Telmatobius jelskii). They were participating in a frog surveying trip for SCBI’s Center for Conservation Education and Sustainability’s Peruvian Biodiversity Monitoring and Assessment Program (BMAP). The program lends Smithsonian scientific expertise to gas and oil companies to assess the effects of development projects on local plants and animals. This information is used to improve restoration work, and reduce environmental impacts of future development. This was the third survey along the path of a natural gas pipeline constructed in 2009 that runs from the Amazon over the Andes to the Pacific Ocean—about 250 miles.

The Acancocha water frog is found only in the cold clear streams of the high-elevation Peruvian Andes. The frog is one of about 40 species researchers are surveying around the construction of this particular pipeline. Scientists chose this species because although historically it has been fairly abundant, it lives in a relatively small area with precise habitat requirements. When individuals of a species are clustered together, it’s easier to lose the entire species.

“You always worry about frogs with small geographic ranges—not just frogs, but any species,” Deichmann said.

When you think of the Peruvian Andes, you probably think of Macchu Picchu, a lush green mountainside where, as Smith jokes, “if you sit too long you have orchids growing on you.” Smith and Deichmann, however, were in a very different ecosystem called puna and sometimes nicknamed equatorial tundra. Puna is found high in the Andes, where trees no longer grow, rain is scarce, and nights are freezing. The team spent much of its time about 15,000 feet above sea level, where the air is so thin that breathing is hard until you get used to it. “For us lowland landlubbers, that alone was an exhausting business,” Smith said.

Peruvian Andes

Smith and Deichmann were in a very different ecosystem called puna and sometimes nicknamed equatorial tundra. (Photo by Jessica Deichmann, SCBI)

The team—Deichmann, Smith and two Peruvian biologists—took samples at twelve sites where the pipeline crosses mountain streams. At each site, they spent about 45 minutes upstream, elbow-deep, feeling for frogs and tadpoles. For each tadpole, first, the team swabbed its mouth for a sample for chytrid testing. The team also recorded the tadpole’s body length, tail length, mass, and developmental stage, and photographed each sample before the animal was returned to the stream.  They also took measurements of the stream itself. Then the team repeated the whole process downstream of the pipeline. Any one site could take five or six hours.

But Deichmann is clear that the process was worth it. “Just to find frogs and tadpoles was exciting,” she said. “Especially adults—after hours and hours in freezing cold water and your arms are purple, when you find your first frog it’s just so exciting.”

The team hasn’t processed the data yet, but their initial measurements suggest some good news: so far, they have seen no obvious effects as a result of the pipeline. However, although the team found hundreds of tadpoles, they found only 10 adult frogs in all the sample areas.

Unfortunately, that suggests chytrid is playing a role in shaping the population structure. The skin fungus follows skin keratin proteins, the amphibian equivalents of those found in human skin calluses, hair and nails. Tadpoles usually survive chytrid infection because they have keratin only around their mouths. As they develop their keratin “suit of armor,” frogs are left vulnerable to the disease that has decimated them in less than half a century.

“From metamorphosis, something called the ‘chytrid clock’ starts ticking,” Smith said. In adults, “chytrid interferes with water balance, usually in a lethal way.” Because of this, chytrid-struck populations often consist of many tadpoles and a few adults.

And according to the previous surveys, “at pretty much all the sites where frogs and tadpoles were present, chytrid was present,” Deichmann said.

Mountain stream

At each of 132 sites, the team spent about 45 minutes upstream, elbow-deep, feeling for frogs and tadpoles. (Photo by Jessica Deichmann, SCBI)

But until they have the results from lab tests on the mouth swabs the team took, they won’t have the full picture about how the disease is affecting these populations.  And chytrid isn’t the only danger these frogs face. “In a lot of our streams we were, not surprisingly but disappointingly, finding trout,” an invasive predator, Smith said.

Deichmann and Smith agree that the data they collected will be useful for conservation efforts. “Monitoring populations now gives us a baseline without which we can never know what’s changed,” Smith said. The team has a tentative follow-up survey scheduled for the dry season of 2012, during the northern hemisphere’s summer. Deichmann hopes that the data from this December’s trip will allow the program to modify the survey protocol to make sure future trips are gathering the most helpful data possible.

And of this expedition? “It was an amazing trip,” Deichmann said. “The habitats are stunning, the scenery is stunning. You’re at the top of the world.”

Meghan Bartels

A United Front in Panama

The Panama Amphibian Rescue and Conservation Project implementation team met in Panama in February. From left: Pete Riger, Alan Pessier, Eric Baitchman, Paul Crump, William, Heidi Ross-Griffth, Angie Estrada, Jorge Guerrel, Della Garelle, Roberto Ibanez (Photo by Brian Gratwicke, Smithsonian Conservation Biology Institute)

Amphibian conservationists convened in El Valle, Panama, last month to plan the future of our fight to save amphibians. We didn’t do any collecting this trip, as frogs are much harder to find during the dry season. Parts of the country, including past collection sites in the Darien region, are also currently too dangerous. Instead, members of the project’s implementation team met with the El Valle Amphibian Conservation Center (EVACC). We are joining forces and looking at ways we can work together as one organization with two campuses.

Dr. Alan Pessier of San Diego Zoo Global facilitated the two-and-a-half day strategic planning session where a SWOT analysis was used to identify the organizations’ combined Strengths, Weaknesses, Opportunities, and Threats. Participants included Heidi Ross, director of EVACC; Roberto Ibañez project director in country; Brian Gratwicke, project coordinator; Angie Estrada and Jorge Guerrel, project staff; Peter Riger and Paul Crump, Houston Zoo; Eric Baitchman, Zoo New England; Della Garelle, Cheyenne Mountain Zoo.

The outcome was an ambitious and detailed action plan to achieve our mutual goals of creating assurance colonies of Panama’s most vulnerable amphibian species, and ultimately re-establishing their healthy wild populations. We plan to expand our ability to house more priority species and breed them reliably, better communicate progress on our work to interested parties, continue to improve husbandry and increase efficiency, identify staffing and equipment needs, prioritize research projects, and develop re-introduction criteria.

Dr. Della Garelle, Director of Conservation, Cheyenne Mountain Zoo

National Zoo Successfully Collects Sperm Samples to Save Endangered Frog

Gina Della Togna, an SCBI PhD student and native Panamanian, is one of the researchers in charge of the sperm collection procedure.

Gina Della Togna, an SCBI PhD student and native Panamanian, is one of the researchers in charge of the sperm collection procedure. (Photo courtesy of the Smithsonian Conservation Biology Institute)

With nearly one-third of all amphibian species at risk of extinction as the result of the deadly chytrid fungus, the Smithsonian’s National Zoo has taken a bold step toward preserving amphibian genes and the world’s incredible amphibian biodiversity. Researchers at the Smithsonian Conservation Biology Institute in Washington, DC, have begun to collect sperm samples from the Zoo’s collection of Panamanian golden frogs (Atelopus zeteki), which are extinct in the wild.

Although researchers have collected sperm samples from other amphibian species such as Mississippi gopher frogs and leopard frogs, there are no publications detailing sperm collection methods from Panamanian golden frogs. SCBI’s colleagues at the Maryland Zoo have aided in the process, providing advice to the SCBI researchers about the method to collect the frogs’ spermatozoa using hormonal stimulations.

“We currently have three other species of Atelopus in captive assurance colonies in Panama,” said Brian Gratwicke, an SCBI conservation biologist who leads the Zoo’s amphibian conservation program to curb global amphibian declines. “If we can freeze some of their sperm, golden frogs will be a model to secure the long-term genetic integrity of other toad species in similar situations.”

Gina Della Togna, an SCBI PhD student and native Panamanian, is one of the researchers in charge of the sperm collection procedure. Even though this is still a fairly new endeavor, Della Togna said she felt that it was easy compared to collecting sperm from mammals. After hormonal stimulation, spermatozoa are excreted in the urine from the frog’s cloaca, a multipurpose opening from which feces, urine and gases are expelled. This is in contrast to mammals, which possess specialized structures for the expulsion of waste and reproduction.

Atelopus zeteki sperm

A Panamanian golden frog sperm

Although sperm collection from this species has been successful, finding the most efficient and repeatable stimulation protocol is critical. Then, identifying the right cryoprotectant and freezing method will be another challenge. Researchers suspect that the cell component most likely responsible for the movement of the sperm, called a mitochondrial vesicle, has a unique structure compared to that of other animals.

“The mitochondrial vesicle is a very fragile structure,” Della Togna said. “Protecting this structure will definitely be one of our greatest challenges.”

Even in the face of numerous challenges, the research team overseeing the sperm collection and storage of the samples remains optimistic.

Pierre Comizzoli, an SCBI gamete biologist supervising the PhD project  is enthusiastic about the prospect of this endeavor and is charged with studying the complex golden frog sperm structure with Della Togna.

“It is always exciting to discover new biological mechanisms,” Comizzoli said. “Spermatozoa from each species have unique traits that needs to be well understood before developing preservation protocols.”

Other than its genetic and natural significance, the Panamanian golden frog is a meaningful symbol of culture for Panamanians. Pre-Columbian peoples used to make golden “huacas,” or sacred objects, in the image of these frogs, along with creating legends about these renowned frogs, which endure in the Panamanian countryside today, Della Togna said.

“This species does not exist anywhere else in the world,” Della Togna said. “You will find pictures and sculptures of it in local markets, in indigenous handcraft sales, and on lottery tickets, among places. Hopefully this project will help to ensure that one day you will be able to see them once again on the banks of Panamanian streams where they belong.”

Phil Jaseph, Smithsonian’s National Zoo