Remnant from the Triassic Period

Tuataras are an Ancient Species Still Living Today in New Zealand

by Annie Shao, age 17

Although dinosaurs no longer roam the earth, the tuatara—a species that existed before the first dinosaurs—still populates New Zealand. This island nation is home to many bizarre creatures, like the kiwi bird and the kakapo. But the tuatara trumps them all in the world of exotic.

The khaki-colored, rough-skinned reptile is about 16 inches in length. Although at first glance, the tuatara looks more or less like an iguana, it is actually vastly different in an evolutionary sense. Scientists have labeled it a “living fossil” because its skeletal anatomy has changed little since hundreds of millions of years ago during the Triassic period, the geological era that preceded the Jurassic period.

Not the average reptile, the tuatara has a uniquely long lifespan. Some have even been known to outlive the giant tortoise that lives for as long as 100 years. Scientists have recorded individual tuataras as old as 200 years, and speculate that some may be even older.

To match their longevity, tuataras have long reproductive periods. A female becomes sexually mature at age 20, and can still reproduce at 80. This lengthy reproductive window does not come without reason: tuataras reproduce slowly. It takes two to three years for unfertilized eggs to develop inside the mother. Once impregnated, the mother gives birth after seven to eight months. The eggs then need to be incubated in the ground for about a year before the baby tuataras emerge.

Tuataras also retain many primitive characteristics. Their heart and lung structures are simple compared to those of other reptiles, and their dental structure is just like that of a dinosaur. While modern mammals and reptiles have tooth sockets, the tuatara’s teeth sprout directly from its mandible. These teeth allow for a different method of chewing. Their single row of lower teeth slide into two rows of upper teeth, cutting like scissors. Perhaps most amazing, tuataras have a third eye on the top of their skull known as a pineal eye. This is a primitive feature. The eye is made up of only a few light-sensitive cells.

Despite its ancient physique, the tuatara’s genome evolves extremely rapidly. Scientists are still baffled by the fact that its DNA has possibly the highest mutation rate of any vertebrate.

Living in an isolated island habitat like New Zealand has also contributed to evolutionary changes in the tuatara species. Tuataras have adapted effectively to New Zealand’s environment. For example, they can withstand near-freezing temperatures. Their hemoglobin—or oxygen-carrying proteins in the blood—and their enzymes, are programmed to operate at low temperatures. Their tolerance for the cold allows them to be nocturnal. At night, they prey on wetas, giant crickets unique to New Zealand.

Currently, about 50,000 tuataras exist in New Zealand where they are considered a national treasure. Herpetologists, scientists who study reptiles, have recorded about 1,000 of them per acre on Stephens Island, a place heavily populated with reptiles.

These primordial reptiles thrive alongside other extraordinary creatures of New Zealand. Although many of their body structures are primitive compared to that of most animals, tuataras and their strange features manage to exist in a modern world.

[Source: The New York Times]
Very interesting article, Annie! Keep up the good work! – Max LienMadison, WI (2011-06-16 18:36)