THREE-TOED TOADLETS: Brachycephalidae

PHYSICAL CHARACTERISTICS

This family includes some of the smallest frogs in the world. Depending on the species, adults grow to just 0.3 to 0.8 inches (0.8 to 2 centimeters) long from the tip of the short, rounded snout to the end of the rump. Although the frogs are small, they have somewhat chunky, strong-looking bodies. Their front legs are thin and end in two, sometimes three, stubby toes. They have the bones for the other two toes under their skin, but these toes do not show. Their hind legs likewise show only three, sometimes four, very short toes. Each toe bone in the four feet is shaped like a "T" at the tip. The skeleton is also a bit odd in these frogs because it has no middle chest bone, or sternum, but does have a covering of bone across the front of the chest. Most species also have bony plates, or shields, under the skin of the back. The shield attaches to the backbone. Because of this shield, the three-toed toadlets are sometimes called saddlebacks. The southern three-toed toadlet does not have the shield.

Several of the frogs in this family, including the southern three-toed toadlet and some of the pumpkin toadlets, are bright orange. The pumpkin toadlet is sometimes yellow instead. The southern three-toed toadlet has black patches along its sides, parts of its legs, and around its eyes. Other frogs in this family are shades of brown and blend into the background a bit better.

Scientists either group all six species into one genus, called Brachycephalus or put two of the species in their own genus, named Psyllophryne. As of 2002, many scientists now use only Brachycephalus because they think all six species are very closely related. At one time, scientists thought that the three-toed toadlets should be part of the "true toad" family, named Bufonidae. When they took a closer look, however, they found that the toadlets were missing an organ that the true toads have. It is called Bidder's organ and is a small growth of female-type tissue on part of the male's reproductive system.

GEOGRAPHIC RANGE

All six species live in different areas within the far eastern part of central and southern Brazil along the Atlantic Ocean coastline.

HABITAT

The tiny frogs in this family live among the leaves that cover the ground of warm, humid forests. They often live in forests on mountainsides up to 2,240 feet (750 meters) above sea level. They also breed on land.

DIET

Members of this family eat various arthropods (AR-thro-pawds). Arthropods are animals without backbones, or invertebrates (in-VER-teh-brehts), that have jointed legs. The diets of most three-toed toadlets include mites and springtails. Mites are small, spider-like arthropods. Springtails (sometimes called snow fleas in colder climates) are a type of very tiny insect that has a little clip on its underside. When the insect quickly unfastens its clip, the creature springs through the air. Three-toed toadlets find mites, springtails, and other small invertebrates in the leaves that are scattered on the ground.

BEHAVIOR AND REPRODUCTION

In the dry season of the year, these frogs find shelter under logs or beneath piles of leaves on the ground. They become active when the rainy season comes and wander about on land during the daytime. They typically walk rather than hop, using their thin front legs and longer hind legs to crawl among leaves on the forest floor. The males set up and defend territories against other males. A male calls to keep intruding males away, but if that does not work, he may begin wrestling with the other male and try to push him out of the area.

Scientists have not done careful studies of all six species, but they think that they probably all reproduce in the same general way. In the breeding period, which also takes place during the rainy season, the males call from their territories on land. The call of the pumpkin toadlet and the southern three-toed toadlet is a buzzy sound. The females hear the calls and approach the males. When a female comes close, a male will climb onto her back and use his front legs to hold onto her in front of her hind legs. The male frog, at least among the pumpkin toadlets, then scoots forward until he is hanging onto her body near her front legs. This type of piggyback grasp is called amplexus (am-PLEK-sus). Once the male is in the right position, the female lays her eggs, which are quite big compared to the size of the frog. She lays them on leaves or sometimes under a log. Because her eggs are so large, the female only has a few eggs. A female pumpkin toadlet, for example, lays five or fewer eggs, each of them 0.2 inches (5.1 to 5.3 millimeters) in diameter. The toadlet that is known by its scientific name Brachycephalus didactyla lays only one egg per clutch. Instead of hatching into tadpoles as happens in many other species of frogs, three-toed toadlet eggs hatch directly into baby toadlets, sometimes with a tiny bit of tail that disappears shortly. Pumpkin toadlets hatch 64 days after the female laid the eggs.

THREE-TOED TOADLETS AND PEOPLE

Scientists are studying the pumpkin toadlet because its skin oozes a poison that might be useful in making some medicines.

CONSERVATION STATUS

The World Conservation Union (IUCN) lists three species of three-toed toadlets as Data Deficient, which means too little information is available to make a judgment about the threat of extinction. The three species are Brachycephalus nodoterga, which is sometimes called a saddleback toad, Brachycephalus pernix, and Brachycephalus vertebralis.

WHEN IS A TOADLET NOT A TOAD?

The three-toed toadlets of South America have a confusing name, because they are not actually toads at all. Scientists group all true toads into a single family, named Bufonidae. Young toads in this family are called toadlets. None of the other species of frogs are true toads, even if they have warty skin and look very much like toads. People who are not scientists, however, often are the ones who give frogs their common names, and they sometimes name warty-looking frogs "toads." The three-toed toadlets are an example. People called them toadlets because they look toad-y and they are small. Three-toed toadlets, however, are not part of the family Bufonidae and, scientifically speaking, are not really toads or toadlets at all.

Brachycephalus nodoterga lives in a very small area. In fact, it has only been found in one place: in forests that have never been cut down and about 3,280 feet (1,000 meters) above sea level. More studies will help scientists learn details about this frog's life and what specific type of habitat and other things it needs to continue to survive in the wild. Brachycephalus pernix also lives in a small area. This species makes its home in mountain forests about 1,475 feet (450 meters) above sea level. Although its entire habitat is inside a protected area, conservationists fear that too many tourists in the forests may be trampling over the leaf-covered ground and accidentally harming the frogs that live there. Brachycephalus vertebralis is the third species listed by the IUCN as Data Deficient. This small frog also lives in the mountain forests of southern Brazil along the coast of the Atlantic Ocean. Its home is about 2,625 feet (800 meters) above sea level. First discovered in the late 1990s, it has not been seen since despite repeated searches. Destruction of the forests in southern Brazil may harm the toadlet, as well as the other two Data Deficient species in this family.

PUMPKIN TOADLET (Brachycephalus ephippium): SPECIES ACCOUNT

Physical characteristics: Reaching just 0.5 to 0.8 inches (1.25 to 2 centimeters) long, the pumpkin toadlet is one of the smallest frogs on the planet. Its name comes from its bright orange color, its warty skin, and its tiny size. Sometimes the frog's color is yellow rather than orange, and people call it a gold frog instead. Its head has a short, rounded snout and two large, black eyes. Beneath the skin of its back, this toadlet has a bony plate or shield that is attached to the backbone. The bony plate led to the third common name of this species, Spix's saddleback toad. Its front legs are thin and end in two, stubby toes. The slender hind legs, which are longer than the front pair, end in three stubby toes. The other toes on their feet are either just nubs or missing altogether. The bones inside the toes are each shaped like a "T" at the tip.

Geographic range: Pumpkin toadlets live in southeastern Brazil along the Atlantic coast.

Habitat: These frogs live and breed in humid, warm forests along the ocean. They spend most of their time in piles of dead leaves that cover the ground.

Diet: Pumpkin toadlets scrounge around in the leaf piles for small arthropods, including mites and tiny insects called springtails. Studies of pumpkin toadlets show that the frogs get more than half of their diet from springtails.

Behavior and reproduction: Pumpkin toadlets, which are active during the daytime in the rainy season, are not difficult to spot. Their bright orange or yellow color is very noticeable as these tiny frogs slowly walk over leaves. If the day is very humid, they may climb onto low branches of bushes and trees. In a rather unusual behavior, this frog swipes its front and back legs over its head on down its body. The frog performs this leg-waving movement when cleaning its body of dirt. A male frog also will wave its front legs in front of its eyes when another male comes close. This sometimes scares off the newcomer. If it does not work, the male will protect his territory by wrestling with and shoving the other male until he leaves.

Each male calls from his own territory during the rainy season. He holds his body up high, draws in air to fill up his vocal sac, and performs his call, which is a repeated buzzing sound. When a female approaches, he wraps his front legs around her waist and then walks with her in this position as she shuffles around looking for a good spot to lay her eggs. Once she finds a site under a log or in a pile of leaves, the male scoots up to grab onto her near her front legs. For the next 30 minutes or so, she lays her eggs. Females usually lay five, large, yellowish white eggs at a time. After the female lays the eggs, the male leaves, but the female stays behind for a few moments to roll the eggs along the ground with her hind feet. Now covered with dirt, the eggs are well-hidden from the view of predators. The eggs hatch 64 days later, skipping the tadpole stage, and small, reddish brown toadlets crawl out. The newborn toadlets have a tiny tail, but this disappears soon.

Pumpkin toadlets and people: Scientists are studying the medical uses of the very strong poisons, or toxins, that ooze from this frog's skin. The toxins affect the heart and other muscles and the nerves.

Conservation status: The IUCN does not consider this frog to be at risk. Although it lives in a fairly small area, the pumpkin toadlet is quite common there. In addition, part of its habitat falls within various protected areas. ∎

FOR MORE INFORMATION

Books:

Mattison, Chris. Frogs and Toads of the World. New York: Facts on File Publications, 1987.

Showler, Dave. Frogs and Toads: A Golden Guide. New York: St. Martin's Press, 2004.

Web sites:

"Brachycephalidae." AmphibiaWeb.http://elib.cs.berkeley.edu/aw/lists/Brachycephalidae.shtml (accessed on March 8, 2005).

"Brachycephalus pernix." AmphibiaWeb. http://elib.cs.berkeley.edu/cgi-bin/amphib_query?query_src=aw_lists_genera_&where-genus=Brachycephalus&where-species=pernix (accessed on March 8, 2005).

Cannatella, David. "Brachycephalidae." Texas Memorial Museum, University of Texas, Austin.http://www.zo.utexas.edu/research/salientia/brachycephalidae/brachycephalidae.html (accessed on March 8, 2005).

"Psyllophryne hermogenesi." AmphibiaWeb. http://elib.cs.berkeley.edu/cgi-bin/amphib_query?query_src=aw_lists_genera_&where-genus=Psyllophryne&where-species=hermogenesi (accessed on March 8, 2005).

Watson, Eduardo Cörner. "Little Frog." http://www.grindelwald.com.br/sapo/ (accessed on March 8, 2005).