Some sponges can live for over a thousand years. Giant tortoises are capable of reaching 200 years old or more. Even humans regularly reach their one hundredth birthday in this day and age. But at the other end of the longevity scale are small animals such as rodents and insects, many of which rarely live longer than a single year.
The shortest lifespan of all is commonly said to be the mayfly, but the notion that these insects live for just one day is false. It is indeed true that mayflies have very brief adult stages although they actually live as nymphs underwater for several months or even years. They go through many moults during this juvenile stage before eventually struggling to the surface of the river where they live and emerging as adults. The males develop colourful wings and long tail streamers to attract females, but neither sex possess mouthparts or even stomachs. The adult stage of the mayfly is designed solely to reproduce – the time for feeding has ended.
Since they have no mouthparts, adult mayflies must rely on the fat reserves they built up as larvae to fuel their flight, so the task of finding a mate becomes a frantic one. There is no time for proper courtship so the males jump on whatever females they can find. But pouncing on females and fertilising their eggs saps their already limited energy and soon the exhausted males are unable to sustain flight. The females last a little longer, just until they have laid their eggs further upstream, but soon the dead bodies of mayflies litter the surface of the rivers, providing a glut of food for fish and other animals. Even humans get in on the action; in parts New Guinea, villagers skim huge masses of post-copulatory mayflies from the surface of the water and cook them to make pancakes.
It isn’t too surprising that people often think mayflies live only for a day, though, since the adult form is usually the only glimpse of them that we get. One species, Dolania americana, probably has the shortest adult lifespan of any animal. After completing its final moult, it must mate, lay eggs, and die – all within about five minutes or so. But although the adult stage is undeniably short, when you view the mayfly’s life as a whole, from hatching to its death, it’s actually quite a lengthy one – for insect standards at least.
In fact, many larger and more complex animals have lifespans that are decidedly shorter than the mayfly’s. Labord’s chameleon (pictured above) from Madagascar lives for a maximum of five months; they hatch in November, reach adulthood in January, and lay their eggs in February. Then the entire adult population dies and the species is represented solely by developing eggs that won’t hatch for another eight months. The seven-figure pygmy goby, a tiny reef-dwelling fish from the Indo-Pacific region, has an even shorter lifespan: no greater than two months, which makes it the shortest-living vertebrate on the planet. These fish bring a whole new meaning to the phrase ‘live fast and die young’, for they are able to reproduce for themselves aged three and a half weeks, and each female can produce three clutches of eggs in her sixty-day life.
But the ultimate record-holder must go to this simple, near-microscopic creature. It’s called a gastrotrich.
Transparent and flat, gastrotrichs don’t do an awful lot apart from swim around eating whatever miniscule particles they can find. They reach sexual maturity after three days and then they reproduce by cloning immediately after. A day or two later, they die of old age. In essence, gastrotrichs live their entire lives within the space of a single week.