The deep ocean harbours some strange beings. Andrea / Flickr Well, this is just horrible.

Scientists have discovered parasites can drive fish from inside their eyeballs – to their own death.

In fact, the parasites, eye fluke Diplostomum pseudospathaceum, control their host for most of its life cycle.

The first stage was discovered back in 2015 by Mikhail Gopko at the Severtsov Institute of Ecology and Evolution in Moscow, who found that young rainbow trout infected by young eye fluke were less active and less likely to be caught by dip-nets.

That works for the young eye fluke because they need their host to survive.

They "are too young and innocent to infect a next host", Gopko told New Scientist.

It’s not the parasite in question, but here’s a pretty horrible example of another type of a fluke living in the eye of a freshwater bully, a fish native to New Zealand:

But a new study by the same team shows the creepy way in which the eye fluke escapes a watery grave as it gets older in order to keep the life cycle turning.

When the eye fluke is ready to reproduce, the host fish suddenly starts swimming a whole lot more, and closer to the surface of the water.

Eye flukes might live inside fish, but they reproduce inside birds. And forcing their hosts to the top of the water makes them a whole lot more likely to find their way into a bird’s gut system.

And when the team simulated bird swoops over the fish, the fish froze, as was natural, but the infected fish started swimming again sooner than those not infected.

Once in the bird’s gut, eye fluke reproduce and their eggs are shed in the bird’s faeces, and hatch in water. They then seek out snail hosts, multiply in the snails, and then start searching for a host fish.

Once they land and penetrate the fish’s skin, the young fluke starts working their way towards the eye lens, where they can strongly influence their host’s behaviour to suit their reproductive needs.

Exactly how they do that is yet to be determined.

Isn’t nature wonderful?