The animal that lives for 10,000 years

Brine shrimp are also not shrimp, but they do belong to the same group, the crustaceans. They are tiny, just 15mm long. They eat algae, which they filter out of the water. They swim upside-down and breathe through their legs, and females do not need a male to reproduce.

Crucially, they have a unique affinity for salt. They can tolerate concentrations up to 50%. Such water is far saltier than the ocean, which is only about 3.5% salt, and the salt will be on the verge of precipitating out as a solid.

The brine shrimp are fine with this.

If you live in a pond, there is always a risk that it will dry out. The pools and lakes brine shrimp inhabit frequently disappear for months, years or decades. This should be a gigantic problem, but the brine shrimp simply dry out.

Male brine shrimp have claspers for holding onto females

When conditions are favourable, female brine shrimp produce thin-shelled eggs that hatch immediately. But when food is scarce or salt levels are rising, they resort to plan B. They produce hard-shelled “cysts”, each of which contains a near-fully-developed larva.

Radiocarbon dating estimated they had been lying there for 10,000 years

These cysts are able to withstand near-total dehydration, losing more than 97% of their water content. All their life processes stop and they enter a state of suspended animation called anhydrobiosis, a bizarre stopover between life and death.

As anyone who has kept sea monkeys as pets will know, to resurrect the embryos you just add water. The cysts take on 1.4 times their weight in less than 24 hours, before hatching into larvae the size of the full stop at the end of this sentence. When they first hatch they have just one primitive eye, though they add two more sophisticated eyes later.

Water is the liquid in which the molecules inside our cells move and mix, giving rise to life-sustaining chemical reactions. So taking it away brings those processes to a halt.

But for most animals, losing too much bodily water doesn’t just shut things down, it causes lethal damage. Humans can only lose 15% of our bodily water, and few animals can lose more than 50%.

As water is removed, the molecules inside our cells lose the three-dimensional network that buoys them up. Proteins, sugars, and chromosomes become warped and break down.

Ice crystals act like tiny knives, ripping cells apart from the inside out

The challenge is to allow molecules to keep their shape as they dry out. For this, brine shrimp have a sweet solution: they turn their cells into solid sugar.

The cysts are loaded with an unusual sugar called trehalose, which makes up 15% of their dry weight. It forms a solid rather like the glass in windows. This “matrix” props up proteins and membranes, maintaining their structures, and freezes them in place.

Trehalose is the magic ingredient uniting most organisms capable of suspended animation, including the near-invincible tardigrades, certain nematode worms, and the larvae of an African fly called the sleeping chironomid.

Source: BBC

N.H.Khider