Microteiids: Gymnophthalmidae

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MICROTEIIDS: Gymnophthalmidae



The microteiids are very small lizards, with adults usually only growing to 2.3 inches (6 centimeters) long from the tip of the snout to the vent, which is a slitlike opening between the two hind legs on the underside of the lizard. Their tails come in different lengths depending on the species, but they are typically about one and one-half times the length of the body from snout to vent or longer. All species in this family can easily break off the tail and grow a new one. Most, but not all, have four working legs. The eighteen species in the group, or genus (GEE-nus), called Bachia have tiny legs, and those in the genus Calyptommatus have no legs at all. A genus is a group of similar species. Although the microteiids spend much of their time hidden in dark places, they have well-formed eyes.

Many species in this family have small scales on their backs and larger scales on their undersides. Some species have ridges, or keels, on their back scales, and some have smooth unkeeled scales. Many have backs in shades of brown or black, and some have stripes or spots. In a few species, such as the golden spectacled lizard of Costa Rica, the tail may be a different color than the rest of the lizard.


Microteiids live in southern Mexico, in Central America, on the Caribbean islands, and throughout much of South America, where they reach as far south as north-central Argentina.


The microteiids live in tropical forests, often by water. They usually stay out of sight under piles of leaves, beneath logs, or in other hiding places and will often dive into the water to escape predators (PREH-duhters), or animals that hunt other animals for food.


These lizards are mainly active during the day and spend much of their time rooting around in leaves and along the ground to find their favorite food insects. They see and smell well and likely use these characteristics to help them find food and to escape predators.


Although this family has at least 175 species, their small size and tendency to remain hidden has helped to keep much of their behavior a secret from scientists. Some have, however, been seen wandering along the forest floor and along the shores of streams and swamps looking for insects to eat. When they feel threatened by an attacker, they will run to the water, where they dive in and swim off. Many have flattened tails, which help them swim quickly through the water. Unlike most other lizards, which sunbathe, or bask, out in the open during the day to warm their bodies, the microteiid lizards apparently do not. Instead, some appear to heat up their bodies by finding a sunny spot and crawling under leaves there.


Scientists do not understand just how important each individual species is to life on Earth. Over the years, the most-studied animals are those that humans find cute and/or want for pets, like dogs and cats; that people find useful, like cows for meat and horses for farm chores; or bothersome, like mosquitoes that transmit disease. Scientists know much less about other species that lack these traits and that stay out of sight. The microteiid lizards are an example. They are small lizards that hide in piles of leaves and rarely come across a person. Even these species, however, are important to the web of life on the planet. For example, numerous predator species probably eat them, and they in turn eat many different types of insects, which eat other animals and plants, and so on. If the microteiid lizards were to disappear, it is possible that the surrounding environment would change so much that it would cause harm to the other animals and plants that live there. This is also true of other species on Earth. No animal or plant lives and dies without having an effect on some other living thing.

Those species that have been studied are all egg layers, and scientists believe that the females only have one or two young at a time but lay eggs more than once a year. Some of the species are all female, which means that they can and do have babies without mating with males. Species that do this are called parthenogenic (PAR-thih-no-JEH-nik). This is rather unusual among lizards and among other vertebrates (VER-teh-brehts), which are mammals, birds, and other animals with backbones. Most vertebrates require that a female and male mate before the female becomes pregnant. In the microteiid lizards, however, a female can become pregnant without ever seeing a male and produces babies that are her exact duplicates. Such exact duplicates are called clones.


People and microteiid lizards rarely come across one another. Sometimes, however, people unknowingly dig in their habitat and can harm the lizards.


These species are not considered endangered or threatened, but scientists know little about them. Because they live along the ground, however, and sometimes in very small areas, habitat destruction can wipe out entire populations.


Physical characteristics: This lizard is known only by its scientific name of Bachia bresslaui. It has a long body and long tail but very tiny, hardly noticeable legs. Its upper body is gray to brown, sometimes with brown spots, and has a tan stripe down either side. It has a cream-colored underside. Unlike many other lizards that have noticeable openings on the sides of the head for ears, this species has no such openings. Of the few individuals that have ever been seen, the largest of this rare species of lizards reached a size of 4.2 inches (10.6 centimeters) in length from the snout to the vent, plus a tail that measured more than 6.3 inches (16 centimeters) long.

Geographic range: They live in the South American countries of Paraguay and Brazil.

Habitat: In their range, which includes the northeastern area of Paraguay and central Brazil, these lizards have been found beneath pastures inside tunnels in sandy soils. Scientists think they may live in other types of soil, too.

Diet: Scientists have studied only five individuals from this species. These five ate ants, scorpions, spiders, beetles, and beetle grubs.

Behavior and reproduction: Although very little is known about Bachia bresslaui, scientists believe these lizards likely leave their below-earth homes and search about above ground for insects and other things to eat. They may walk with their small legs or slither like snakes. Scientists also guess that the females lay eggs rather than have baby lizards, but they have not yet found the eggs. They are also unsure about how many eggs the lizards lay at a time.

Bachia bresslaui and people: People and this lizard rarely see one another. Humans do, however, sometimes destroy their habitat when they build on or otherwise change the areas where the lizards live.

Conservation status: This species is not considered endangered or threatened. Scientists suspect that this species may actually live in areas other than northeastern Paraguay and central Brazil, but they do not have proof as yet. ∎



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"Genus Bachia." Animal Diversity Web. University of Michigan Museum of Zoology. http://animaldiversity.ummz.umich.edu/site/accounts/classification/Bachia.html (accessed on November 15, 2004).

"Golden Spectacled Lizard (Gymnophthalmus speciosus)," Savannah River Ecology Laboratory Herpetology Program. http://www.uga.edu/srelherp/jd/jdweb/Herps/species/Forlizards/Gymspe.htm (accessed on November 12, 2004).

"Gymnophthalmidae." Animal Diversity Web. University of Michigan Museum of Zoology. http://animaldiversity.ummz.umich.edu/site/accounts/classification/Gymnophthalmidae.html (accessed on November 15, 2004).