Jellyfish are infamous for their stinging abilities. The sting of some species, such as the sea wasp, can cause cardiac arrest in humans, and the victim will drown before evening getting to shore. However, jellyfish’s powerful stinging abilities are a two way street.
Jellyfish are cnidarians, which means they are related to sea anemones and corals, and as such, some animals are immune to their sting. Like clownfish, which are immune to the stings of certain sea anemone species, some baby fish are immune to the stings of certain species of jellyfish. Have a look at these baby fish hiding inside the bell of a jellyfish to evade hungry trumpetfish and other reef predators:
This probably goes against much of what you’ve known about jellyfish. After all, there was a scene in Finding Nemo, where Marlin and Dory brave a massive horde of purple jellyfish and nearly die in the process. And, for the most part, jellyfish are extremely dangerous to most fish.
However, for these smaller fish, the jellyfish’s sting is all that stands between them and certain death. Like clownfish using a sea anemone’s tentacles for refuge, these baby fish use the jellyfish’s tentacles as a sort of “electric fence” to keep their predators out.