Giant tortoises are characteristic reptiles that are found on two groups of tropical islands: the Aldabra Atoll in Seychelles and the Galapagos Islands in Ecuador (a population at the Mascarene Islands was exterminated by the 1900s) . Giant tortoises originally made their way to islands from the mainland; for example, Aldabra Atoll and Mascarenes giant tortoises are related to Madagascar tortoises while Galapagos giant tortoises are related to Ecuador mainland tortoises.
This phenomenon of excessive growth is known as islands gigantism or insular gigantism.
Adwaita tortoise carbon dating
comes from Sebastos, which is Greek for ‘magnificent’.
They evade predators by hiding in caves and crevices on the seafloor, but one individual couldn’t evade fishermen off the coast of Alaska.
The maximum lifespan of the Naked mole rat is over 30 years – while not sounding remarkable, it is when compared to other rodents, as it lives about nine times longer than similarly sized mice. Breeding females are fertile until death and, unlike every other mammalian species, their mortality risk does not accelerate with age.
As they are much more closely related to us than any other negligibly senescent organism, understanding how this evolved may improve our understanding of ageing in humans, or even help us to achieve negligible senescence ourselves. Strictly speaking, no animal is truly immortal as all can be killed by accidents, predator attacks, disease or adverse environmental factors.
Only 250 years ago there were at least 20 species and subspecies in islands of the Indian Ocean and 14 or 15 subspecies in the Galápagos Islands.
Although often considered examples of island gigantism, prior to the arrival of Homo sapiens giant tortoises also occurred in non-island locales, as well as on a number of other, more accessible islands.Yet some animals don’t seem to age at all, and have a stable or decreasing rate of mortality as they grow older.These animals are said to be ‘biologically immortal’. Tiny, simple freshwater animals, hydras reproduce asexually by growing clones of themselves and can regenerate – if cut apart, each piece develops into a new hydra.These animals belong to an ancient group of reptiles, appearing about 250 million years ago.By the Upper Cretaceous, 70 or 80 million years ago, some had already become gigantic.As its name suggests, the Aldabra giant tortoise is one of the largest tortoises in the world.