Salamander Biogeography

Salamanders are conspicuously absent from several land masses. There are no salamanders in Australia, nor is there any in sub-Saharan Africa or Madagascar. The reasons for this are linked to the types of habitat and climate that salamanders prefer.

Salamanders reach their highest levels of diversity in the temperate parts of the New World, specifically in the United States and Mexico. In general salamanders prefer cooler temperatures so upland regions like the Appalachians are areas with large numbers of species and individuals. Representatives of all but one family of salamanders can be found in the United States and several families are endemic. The family of lungless salamanders, the Plethodontids, can be found all across the New World, although it reaches its highest levels of diversity in North America, several genera extend down into Central and South America. Lungless salamanders can also be found in Europe and in 2005 a species was described from Korea.

Like the lungless salamanders, other families have disjunct global distributions. The giant salamanders, the Cryptobranchids, have representatives in China and Japan, as well as the United States. The salamandrids can be found in Asia, Europe, North Africa, and North America. Many new discoveries are likely that will enable us to better understand these patterns.

Salamander Biology

Any one can recognize a frog, they have a relatively standard body form, but Salamanders display a tremendous amount of morphological and ecological variation.For example, take the giant salamanders of Asia and North America.They are large, robust species with wrinkly skin, four limbs, small eyes, and a wide, flat head. Compare this to the Siren’s of the United States who have only two reduced front limbs, external gills and are cylindrical in body shape. One might not guess at first sight that they were both salamanders.

The variation doesn’t stop there, the newts of Europein the genus Triturus are a colorful bunch any time of the year, but during the breeding season they undergo rapid and drastic morphological changes. The males develop crests on top to their backs and they take to a completely aquatic lifestyle. Fire salamanders range all across Europe and depending on different environmental variable have different reproductive strategies. For example, some populations as higher elevations will give birth to juvenile salamanders that have already completed metamorphosis, whereas other populations will deposit larvae of various stages into a pond. Some species of salamander never complete metamorphosis and are known as neotenic. The mudpuppies, waterdogs and olm of the family Proteidae are completely aquatic. Some species completely lack a free-living larval stage. Species in the neotropical genus Bolitoglossa lay eggs that the salamanders complete metamorphosis in before hatching.

Why Should You Care About Amphibians?

Amphibians are a critical part of a healthy natural world. In addition to their intrinsic value as abeautiful part of nature, they offer many benefits to us:

• They play an important role in the food web as both predator and prey, maintaining thedelicate balance of nature. Where they are disappearing, detrimental effects are already being documented.
• Amphibians eat pest insects, benefiting successful agriculture around the world and minimizing the spread of diseases, including Malaria and West Nile Virus.
• The skin of amphibians has substances that protect them from some microbes and viruses, offering possible medical cures for a variety of human diseases, including AIDS.
• Biologists refer to amphibians as “the canary in the coal mine:” They are among the first species to be affected by environmental stressors; so when they show declines in the wild, it serves as a warning to other species, including humans. Amphibians’ skin is highly permeable, allowing them to drink and breathe. Unfortunately, contaminants also readily enter the body, making amphibians an exceptional indicator of environmental quality. They are particularly sensitive to pollution, making them important sentinels to potential human threats.
• Frogs have had a special place in various human cultures for centuries, cherished as agents of life and good luck.

Content from www.amphibianark.org

And they sure do look pretty…

Harlequin Frog Rescue Mission #2

The second half of our expedition with Jeff Corwin and the film crew from Animal Planet was to El Cope in Panama s Omar Torrijos National Park. There we searched for the orange-and-black harlequin frog known as Atelopus varius. Several years ago amphibian populations at El Cope were struck by an epidemic fungus and a number of species were largely or entirely wiped out. However recent reports suggested that Atelopus varius tadpoles had been observed in one or more stream pools and that the species was just barely hanging on. Our search here was principally for adult males that might serve as mates for six gravid egg-bearing females maintained at the El Valle Amphibian Conservation Center although we didn t hold out very much hope for success. Male harlequin frogs spend almost all their time in the stream thus they are the first to succumb to the water-borne amphibian chytrid fungus. Adult females which spend much of their time in the surrounding forest venture down to the stream only during the mating season apparently minimizing contact with the fungus and surviving longer than their mates. We did not find any adult males but we did collect about a dozen froglets which must have just metamorphosed from tadpoles. In addition we found a sub-adult female. Our finds offer some hope for the future of harlequin frogs at El Cope since these individuals somehow managed to survive in an environment that was once swept by an epidemic fungus. Perhaps the disease has run its course Perhaps these individuals have developed a resistance to infection Tests will help us determine the answers to these questions and the results may help us save a species that otherwise faces the serious threat of extinction.

Harlequin Frog Rescue Mission #1

The amphibian genus Atelopus – commonly referred to as harlequin frogs - contains approximately 80 species, more than sixty of which are Critically Endangered according to the IUCN Red List of Threatened Species.  No other group of frogs, toads or salamanders in the world teeters as precariously on the brink of extinction.  Harlequin frogs inhabit the tropical forests of Central and South America. Six species are native to Panama where the Houston Zoo is conducting an ambitious amphibian rescue effort.

During the first week of April, Bill Konstant, Director of Conservation and Science, joined with Edgardo Griffith, Director of Panama’s El Valle Amphibian Conservation Center (EVACC), to search of two very rare harlequin frog species.  Bill and Edgardo were accompanied by Animal Planet’s Jeff Corwin, who is filming a documentary for Discovery Channel entitled Vanishing Frogs that should air sometime this fall 

The first site the team visited was Sierra Llorona, which has not yet been infected by the deadly chytrid fungus that has decimated amphibian populations throughout the New Worldtropics.  The team was looking for Atelopus limosus, a small green-and-black species that was discovered in 1995 and inhabits the banks of briskly flowing, rocky mountain streams.  Bill and Edgardo were looking for female frogs, specifically, since the captive colony at EVACC contained only males. Early in the afternoon of April 4^th, they found the first of four small females and went on to collect an additional four males.  Although Edgardo has been conducting amphibian surveys throughout various parts of Panama or the last decade, these were the first female Atelopus limosus he had ever laid eyes upon.  Hopefully, they will become the founders of a sustainable breeding colony.   

Salamander Diversity

Salamanders come in second behind anurans when it comes to the number of species on the planet. There are approximately 560 species described, that’s a 10 times less than the number of frogs and toads. Salamanders are broken down into nine families, and as you’d expect, less than the forty-five anuran families.The largest salamander in North America is the two-toed Amphiuma. These eel like amphibians grow to nearly four feet long. Hellbenders are sometimes thought of as the largest, and whilst they are probably the heaviest, they only reach 2 and half feet long.

Frogs and toads come in second, however, when it comes to size. The largest amphibian on the planet is the Chinese Giant Salamander. These creatures can reach 6 feet in length and inhabits the cool flowing, forested streams of China.Over exploitation for human consumption is threatening the existence of these magnificent animal. Giant salamanders can also be found in Japan.The smallest species of salamander in the world is a species of lungless salamander from Mexico. This species has no common name, its scientific name is Thorius arboreus and can reach maturity at 15mm in length

How do you tell the difference between a lizard and a salamander?

Lizards and salamanders may look alike, but they represent two separate classes of animals and are as different from one another as you are from an ostrich.

True, the typical lizard and salamander has four legs and a long tail, but the similarities pretty much stop there. The lizard is a reptile and the salamander is an amphibian. If you visit your local zoo, you should be able to observe both creatures in the same building, perhaps even side by side.

If you look closely, starting at the head, it becomes clear very quickly that the lizard is a very attentive animal, turning its head this way and that, trying to follow potential predators and prey with its eyes. The salamander, by contrast, doesn’t seem nearly as interested in its surroundings and tends to stare straight ahead. Lizard legs typically are much longer and more muscular than salamander legs, so lizards can really dart about and put on a burst of speed, while salamanders usually just plod along, step by step.

A lizard’s skin is dry and its body is covered in scales.  Salamander skin is scaleless, smooth and moist to the touch. Lizards are often seen in broad daylight basking in the warm rays of the sun. Salamanders, on the other hand, are secretive, spending much of their time beneath logs and stones, underground or in the water. A good number of salamander species live entirely in the water, but only a handful of lizards have adopted an aquatic lifestyle.

Lizard tails are usually long and thin, often whip-like. Salamander tails tend to be a bit shorter and plumper. Tails of aquatic species may even be flattened vertically into the shape of a paddle or a rudder, which helps its owner swim through the water. There is one interesting thing that the tails of certain lizard and salamander species have in common. They can break off completely at certain points and then re-grow some of what has been lost. We call this process regeneration.

   

Here a frog, there a frog, everywhere a frog, frog!

Although the first amphibians emerged from ancient seas that covered much of our planet several hundred million years ago, none of the living species inhabit salt water. Twenty-first century amphibians are creatures of a wide diversity of freshwater, forest, desert and mountain environments of good old terra firma. Frogs and toads, in fact, can be found on every continent but one – Antarctica - and are the most widely distributed of the three amphibian orders.

Frogs and toads are able to survive in some rather extreme habitats. At altitudes greater than 12,000 feet in the Bolivian and Peruvian Andes, a large aquatic frog makes its home hundreds of feet below the surface of Lake Titicaca’s icy, oxygen-poor waters. At the other end of the spectrum, a number of hardy toad species have adapted to life in the hot, dry desert regions of the world. In their effort to withstand week after week of intense heat and little or no rain, many of these species spend the daytime hours buried underground, where the temperatures are relatively cooler and the chances of drying up are slimmer. Some animals even enter an inactive condition known as aestivation, in which they can remain dormant for a year or more before finally coming to the surface.

Then there are frogs that can live up to a hundred feet above the earth in the canopy layers of the world’s tropical rain forests. Although levels of precipitation are high in such environments, reliable water sources are sometimes hard to find and these species often have to rely on plants like bromeliads to capture the precious raindrops that ensure their survival.

Anuran Diversity

The question often comes up, “What is the difference between a frog and a toad?”  The answer,  surprisingly, is not so simple.Together, frogs and toads belong to the Order Anura – amphibians that lack tails.  Technically speaking, all anurans are considered frogs, but some are given the common name “frog” and others are more commonly referred to as “toads”.  If you ask a herpetologist (someone who studies reptiles and amphibians), he or she will tell you that true frogs tend to have smooth skin, bulging eyes and long strong legs, and they lay their eggs in large jelly-like masses. Toads, on the other hand, tend to be stocky, have warty skin, possess shorter hind legs, and lay their eggs in long strands. 

The world’s tiniest frog has no common English name, only a Latin name given to it by scientists. A full-grown adult Eleutherodactylus iberia are black with yellow stripes along their sides and legs and can easily fit on a dime with room to spare.    In its tropical forest habitat, it is typically found hiding in dense leaf litter where it feeds on even tinier insects. Unfortunately, this species is known only from a few locations in southern Cuba and is critically endangered. The title of “World’s Largest Frog” belongs to the goliath frog of West Africa, which can grow to  more than a foot in length (from the tip of its snout to its vent) and weigh close to seven pounds.  It has also been known to leap as far as 20 feet in a single jump.The goliath frog likes to live in fast-flowing streams and is often found near waterfalls.It is hunted for food in the countries of Cameroonand Equatorial Guinea, often commanding a higher price than other forms of bushmeat. Oh, by the way, it would take more than 1,500 of the world’s smallest frogs to equal only one of the world’s largest in terms of size and weight!

Vertebrate Diversity

The Animal Kingdom is broken down into a number of different groups called phyla, one of which is Chordata – animals that have a backbone and a spinal cord that runs through it. The common name for these animals is vertebrates. 

There are five main classes of vertebrate creatures in the world.  Bass, salmon, catfish and trout belong to the Class Osteichthyes, the bony fish.  Snakes, lizards, turtles and crocodiles belong to the Class Reptilia, the reptiles.  Robins, crows, hawks and eagles belong to the Class Aves, the birds.  Sea lions, bats, lions, elephants and human beings belong to the Class Mammalia, the mammals.  And frogs, toads, salamanders, newts, hellbenders, mudpuppies, sirens, amphiuma, axolotls and caecilians belong to the Class Amphibia, the amphibians.

If we consider the number of living species, the largest by far of the five classes is Osteichthyes with  about 20,000 different kinds of fish.  Aves is the next most numerous with over 10,000 species of birds.  Reptiles rank third with more than 8,000 species, and amphibians and mammals bring up the rear with approximately 6,000 and 5,000 species, respectively. 

Every day, scientists discover and describe new species of all kinds, so the numbers above will increase as researchers continue to explore little known parts of the planet.

Photo courtesy of KOCP