Commonly mistaken for a lizard for its appearance, the tuatara is a reptile endemic to New Zealand. A team of researchers conducted the largest vertebrate genome sequence analysis to link the modern species to snakes and lizards from 250 million years ago during the Triassic period.
A collaboration between the University of Adelaide, Otago University, and the South Australian Museum studied the rare tuatara, which means 'peaks on the back' in the Maori language, an indigenous tribe from New Zealand. Their paper was published in the journal Nature.
Tuataras mature slowly and live up to 60 to 100 years old. Their greenish-brown skin closely associates them with other reptiles with distinct spines on their backs.
The last living relative of the tuataras lived 65 million years ago. Today, only two species remain - the more common Sphenodon punctatus and the Sphenodon guntheri, or Brothers Island tuatara. which live on North Brother Island.
Tuatara Genome
The genome sequence analysis linked the only living species of the Rhynchocephalia to dinosaurs, modern reptiles, birds, and even mammals. Genetically, the tuatara is half mammal and half reptile, meaning that the species separated from other ancient reptiles millions of years ago during its evolution.
Professor David Adelson from the University of Adelaide found it remarkable that the tuatara genome 'shares features with those of mammals such as the platypus and echidna.' At the same time, they are the last living species from a reptile group that co-existed with dinosaurs.
'Jumping genes,' or DNA sequences that change location, were discovered in the genome analysis. Some genes resembled the platypus while others were similar to those found in lizards.
Almost 1% of the jumping genes were the same ones found on placental mammals, like humans, explained Adelson. About 4% of the jumping genes resembled reptiles and 10% resembled monotremes, or platypus and echidna species.
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'Highly Unusual' Genetics
The discovery was both 'high unusual' and 'an odd combination' of genetics, said Adelson. Dr. Terry Bertozzi of the South Australian Museum said, ''The unusual sharing of both monotreme and reptile-like repetitive elements is a clear indication of shared ancestry albeit a long time ago.'
Finally understanding the genetic makeup of the last tuatara species has given it a certain, evolutionary position in the tree of life, explained geneticist Neil Gemmel from the University of Otago. The team went through five gigabytes of genetic data, discovering that the tuatara genome is 67% larger than the human genome.
They were also interested in the long lifespan of tuataras, sometimes living beyond 100 years old. Some genes were found to protect the species from aging, such as resistance to disease.
It was also significant that the local iwi Ngātiwai (a Maori tribe), scientists, and conservators worked together for the preservation of the rare tuataras. Adelson said, ''While this is largely fundamental science, I expect it to yield new ways of thinking about our own genome structure that may have relevance to our health.'
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