Wild Tracks

On behalf of the world's wild species

Respect The Jellies

If someone asked you to name the most venomous animal in the world, what would you say? The rattlesnake? A spider or scorpion?

Molecule by molecule, the most deadly animal in the world is a small, translucent animal called a box jellyfish.

Animal venom generally strikes in only one way – it affects the nerves or the blood vessels or the heart or the skin. Box jellyfish venom, on the other hand, is a combination of every known type of poison, affecting every single part of the body. No antidote can ever be designed, as the chemical structure of their venom is just too complex.

Populations of box jellies, along with every other type of jellyfish in the world, are on the increase. Swarms of billions of jellyfish are blooming in every ocean, choking out entire ecosystems and driving out all other forms of life. Of the 2000 species recognized to date, 70 of them are venomous, even deadly to humans.

  • last winter, an 11 metre deep swarm of mauve stingers covering an area of 25 sq km overwhelmed a salmon farm in Ireland, killing 100,000 fish
  • in the summer, beachgoers in southwest England were warned about the presence of highly poisonous Portuguese man of wars
  • studies of mauve stinger swarms in the Mediterranean show that they have now begun blooming in autumn/winter, in addition to spring/summer
  • billions of huge namora jellyfish have bloomed over the past 40 years in the sea of Japan, with drastic effects on the fishing industry

There is a growing scientific consensus that the size and frequency of swarms is increasing all over the world.

Ocean dead zones - red means dead, yellow means threatened.

Ocean dead zones - red means dead, yellow means threatened.

Around the globe, dead zones in the ocean are growing. These oxygen-depleted coastal areas are caused by fertilizer and industrial run-off, pollution, sewage and storm water drainage. Once the oxygen has been taken out of the water, nothing can live in it. Except jellyfish.

Other swarms occur in areas where predators such as swordfish, tuna and turtles (all of which eat jellyfish) and smaller fish such as sardines and whitebait (which compete for food) have been depleted by over fishing.

Laboratory studies have shown that the smallest change in anything – temperature, chemicals, salinity, food, light or environmental conditions – cause swarms of jellyfish to bloom. Warmer water and changing currents due to climate change are also influential in their increase, as well as allowing them to follow their food further north than usual.

Incredibly, scientists in Australia have managed to attach a radio transmitter to a box jellyfish. They discovered these animals are not aimlessly drifting with the current as was once thought. They are actively controlling their own movements, and they are hunting.

Jellyfish apparently have no brains (as we know them, at least) or eyes, but they are well on the way to taking complete control of our oceans.

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