Eight things the jellyfish pulls off without a brain. · Deep Cuts

These jellyfish chase the sun across a lake each day

In a saltwater lake in Palau, millions of golden jellyfish make the same journey every day. At dawn they swim east toward the light, and as the sun crosses overhead they turn and follow it west, stopping just short of the shaded shore. They are farming: tiny algae living inside their tissue make food from sunlight, so the jellyfish steer their gardens into the brightest water and slowly rotate to give every cell its share.

Jellyfish born in space couldn't find their way home

In 1991 a space shuttle carried jellyfish polyps into orbit, where they budded into about 2,478 baby moon jellies. A jellyfish tells up from down with tiny crystals that roll inside little pockets ringed by sensing hairs. The space-born jellies grew these organs, but having never felt gravity they pulsed and tumbled abnormally once back on Earth, an early warning about raising living bodies far from the planet's pull.

A swarm of jellyfish can shut down a power station

Coastal power plants pull in huge volumes of seawater to cool their machinery, and a dense bloom of jellyfish can clog the intake screens in a matter of hours. In 2013 a swarm forced the shutdown of a reactor in Sweden, the largest of its kind in the world, and workers hauled tons of jellyfish off the grates. It had happened at the same plant before, and clogged intakes have stalled stations around the globe.

This jellyfish has 24 eyes and watches the sky

A box jellyfish carries twenty-four eyes in four clusters, and some are surprisingly advanced, with lenses much like our own. Four of them are weighted so they always point straight up, no matter how the animal tilts. They peer through the water's surface to fix on the mangrove canopy overhead, which the jellyfish uses as a landmark to stay near the roots where its food lives. Hide the canopy and it loses its way.

This jellyfish stings you without ever touching you

Swimmers near upside-down jellyfish sometimes feel a prickling "stinging water" with nothing in sight. In 2020 scientists found the cause: the jellyfish releases mucus packed with tiny self-propelled balls of stinging cells. Spun along by little hairs, these specks drift freely through the water and sting prey and skin on contact, long after they have left the animal that made them.

Its tentacles can outstretch a blue whale

The lion's mane jellyfish trails the longest tentacles of any animal. A giant that washed ashore in Massachusetts Bay in 1870 had a bell over two meters across and tentacles measured at about 36.5 meters, longer than a blue whale is from nose to tail. They hang in eight dense bunches of seventy to a hundred and fifty strands, forming a vast drifting curtain to snare passing prey.

The man o' war isn't one animal but a colony

The Portuguese man o' war looks like a jellyfish but isn't one. It is a floating colony of separate bodies called zooids, all grown from a single egg and all genetically identical. One forms the gas-filled float, others do the hunting, the digesting, the breeding. None can survive alone; each depends on the rest as if it were an organ. Together they behave like a single creature.

A jellyfish this heavy capsized a fishing boat

Off Japan a giant jellyfish grows up to two meters across and as heavy as 200 kilograms, about the weight of a full refrigerator. In big years they choke fishing nets by the thousand. In 2009 a three-man trawler tried to haul up a net packed with them, and the load was so heavy it capsized the ten-ton boat; the crew was pulled from the sea by another vessel.