FLORIDA WORMLIZARD: Rhineuridae

PHYSICAL CHARACTERISTICS

Florida wormlizards, the only living species in this family, are long and thin creatures without legs. They have thin rings circling their round bodies, no ear openings, and usually no visible eyes. This combination of features makes many people confuse them with earthworms. Florida wormlizards, however, have scales, and worms do not. In fact, it is the scales on the wormlizard's head that cover its eyes. The head is hard and somewhat flattened with a bladelike front edge, which helps the lizard to dig into the soil. The upper jaw sticks out farther than the lower jaw, so the animal has an overbite of sorts. The shape of the head has caused some people to call them shovelnose wormlizards. They are usually a pearly pinkish white color, but some individuals may be tinted slightly orange-pink. Their heads and tail tips are sometimes a bit darker. Like most snakes, they shed their skin—actually just the top layer of skin—in one piece.

Adults can grow to about one-half inch (1.2 centimeters) around at the middle of the body and reach 9.5 to 11 inches (24 to 28 centimeters) long, including a short tail. The tail begins at the vent, a slit-like opening on the underside of the animal, and is only about one-tenth of the total length of the wormlizard. The tail, which is slightly flattened, is covered on top with little cone-shaped bumps called tubercles (TOO-ber-kuls).

Inside the body, Florida wormlizards look much like other types of wormlizards, which are all grouped together under the name amphisbaenians (am-fizz-BAY-nee-ens). The amphisbaenians include four different families of wormlizards: the Rhineuridae, or Florida wormlizards; the Bipedidae, or mole-limbed wormlizards; the Trogonophidae, or spade-headed wormlizards; and Amphisbaenidae, which are known simply as worm lizards. The Florida wormlizard is the only amphisbaenian that naturally lives in the United States. The others live in Africa, Central and South America, and a few places in Europe and Asia. All amphisbanians are long, thin reptiles that look much like worms, but with scales. They have an odd ear set-up in which parts of the ear attach to tissue on the sides of the face. When the ground vibrates, the tissue senses the vibrations and sends them on to the ear, so the animal can actually hear the ground move. In addition, amphisbaenians have two lungs like almost all other vertebrates (pronounced VER-teh-brehts), which are animals with backbones, but one of their lungs is either extremely small or missing altogether. This arrangement works well in these species, and indeed in many snakes, that have very thin bodies without room for two side-by-side lungs. They also have a forked tongue, no visible ear holes, and one center tooth in the front of the upper jaw that is bigger than the other teeth. The Florida wormlizards sometimes have one little tooth on either side of the center tooth. Florida wormlizards also have their nostrils toward the bottom of the head rather than on the top as many other reptiles do.

GEOGRAPHIC RANGE

Once thought to live only in north-central and northeastern Florida, scientists now know that it also exists in southern Georgia.

A GREATER PAST

The only species of the family Rhineuridae makes its home in parts of Florida and in southern Georgia, but this family once lived over a much larger area. Scientists have identified fossils from wormlizards in the central and western United States. These fossils, which date back as much as 60 million years ago, tell scientists that the wormlizards of the past looked quite similar to the Florida wormlizard alive today. They also were a little different. For example, while they had the same flattened and somewhat pointy skull that the current species has, the fossil worm lizards also had at least one bony feature that Florida wormlizards lack. In their skulls, the fossil wormlizards have orbit and jugal (JEW-gul) bones, that form a complete ring around the eye.

HABITAT

Florida wormlizards make their homes in the sandy and loose but rich soil of usually dry pine and broad-leaved forests. They are burrowing animals and therefore spend most of their time underground. When heavy rains drench the forests, these worms often leave their tunnels and venture out above ground. Because people usually only see them after a downpour, they sometimes call the animals thunderworms.

DIET

Scientists are unsure exactly what Florida wormlizards eat, but they believe they probably eat the same things that other amphisbaenians eat. Most amphisbaenians travel through their underground burrows looking for and dining on the ants, termites, and grubs that they find there. The Florida wormlizards flick their forked tongues to pick up chemicals in the air and on the ground. They then press the tongue on the roof of the mouth, where a special organ, called a Jacobson's organ, lies. This organ "tastes" the chemicals to tell the wormlizard about the prey animals that might be nearby. They also use their special ear set-ups to "hear" even very faint vibrations in the ground. This super-hearing ability probably helps the wormlizards to hear movements made by even very small insects and therefore makes them especially good hunters.

BEHAVIOR AND REPRODUCTION

Florida wormlizards stay underground most of the time, although they sometimes—and just for a moment—poke their heads up and out of piles of leaves. Scientists call such underground-living animals fossorial (faw-SOR-ee-ul). Florida wormlizards dig through the soil with their hard, shovel-shaped heads. The snout is also very hard and forms a sharp edge for tunneling. Although its tail is short, the Florida wormlizard uses it well. As the wormlizard begins digging, its tail is often exposed on top of the ground. Fortunately, dirt fits between the cone-shaped bump on the top of the tail and helps to hides it from the sight of passing predators (PREH-duh-ters), or animals that might hunt it for food. If a predator comes too close, the wormlizard quickly digs further into the soil and uses its tail like a cork to plug the tunnel entrance. Unlike many lizards, the Florida wormlizard cannot drop its tail.

Female Florida wormlizards lay eggs, usually two at a time, in their underground burrows. The eggs hatch into babies about 4 inches (10 centimeters) long. Scientists know little else about their courtship, mating, or reproduction.

FLORIDA WORM LIZARDS AND PEOPLE

People rarely see these shy animals, but they may get some benefits from the wormlizards. If they eat ants, termites, and beetle grubs, the wormlizards may be helping to rid gardens and parks of some of humankind's pests.

CONSERVATION STATUS

This species is not considered endangered or threatened.

FOR MORE INFORMATION

Books:

Behler, John, and F. Wayne King. "Worm Lizard (Rhineura floridana)." National Audubon Society Field Guide to Reptiles and Amphibians. New York: Alfred A. Knopf, 1979.

Burnie, David, and Don Wilson, eds. The Definitive Visual Guide to the World's Wildlife New York: DK Publishing, 2001.

Conant, Roger. A Field Guide to Reptiles and Amphibians of Eastern/Central North America. Boston: Houghton Mifflin Company, 1975.

Gans, C. Biomechanics: An Approach to Vertebrate Biology. Philadelphia: J. B. Lippincott Company, 1974.

Halliday, Tim, and Kraig Adler, eds. The Encyclopedia of Reptiles and Amphibians. New York: Facts on File, 1986.

Schwenk, K. In Feeding: Form, Function, and Evolution in Tetrapod Vertebrates. San Diego: Academic Press, 2000.

Vanzolini, P. E. Evolution, Adaptation and Distribution of the Amphisbaenid Lizards (Sauria: Amphisbaenidae). Ph.D. diss. Harvard University, 1951.

Web sites:

"Animals of the Florida Scrub: Florida Worm Lizard." Flori-Data. http://www.floridata.com/tracks/scrub/animals/rhi_flor.htm (accessed on November 23, 2004).

"Suborder: Amphisbaenia." Georgia Wildlife Web. http://museum.nhm.uga.edu/gawildlife/reptiles/squamata/amphisbaenia.html (accessed on November 23, 2004).

"Wildlife: Florida Worm lizard." Native Florida. http://www.nsis.org/gallery/wl-fl_worm_lizard.html (accessed on November 23, 2004).

"Worm lizard." Fact Monster. http://www.factmonster.com/ce6/sci/A0852748.html (accessed on November 23, 2004).