MadagascarMadagascar chameleon spends most of its life as egg
A bizarre species of chameleon that spends most of its short life as an egg has been discovered by conservationists in Madagascar.
The unusual reptile, known as Labord's chameleon, develops inside an egg for up to nine months, but after hatching lives only a few months longer, during which it rapidly matures, mates and dies.
Because the chameleons hatch at the same time, the population is the same age, apart from a very brief period when adults are still alive after laying their eggs.
Kristopher Karsten, a zoologist at Oklahoma State University, working with scientists in Madagascar and at the American Museum of Natural History in New York, discovered the reptile's unusual lifestyle during field studies over five seasons in the arid south west of the island.
Hatchlings emerged at the beginning of the rainy season, around November, and quickly reached sexual maturity within two months. But by the beginning of February, the chameleons had already started to show signs of old age, becoming slower, losing weight and occasionally falling out of trees because their grip had weakened. Some were found dead on the forest floor from unknown causes.
The unusual life cycle of the chameleons is more similar to insects than reptiles or other tetrapods, the researchers said.
A survey of more than 1,700 other tetrapods - animals with four limbs and a backbone - failed to find any others that have such a short lifespan. During the dry season, the population of Labord's chameleons is made up of developing eggs.
Writing in the US journal Proceedings of the National Academy of Sciences, the team admit it is unclear why the animal has such a bizarre life cycle, but believe it may have compressed its lifespan and resorted to spending much of it inside in an egg to cope with extremes of weather in Madagascar.
A short lifespan might have been the ancestral norm among chameleons, with related species only living longer once they had spread out to regions where variations in the seasons were less harsh, the authors add. If this is the case, it might explain why many chameleons die rapidly in captive breeding programmes. "The notorious rapid death of chameleons in captivity may, for some species, actually represent the natural adult life span," the authors write.
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