A sea swallow and blue button in Coffs Harbour, New South Wales, Australia

© Gary Bell/Minden Picture

Info. A sea swallow feeding on a blue button in Coffs Harbour, Australia

We’re watching a Glaucus atlanticus (common names include ‘sea swallow’ and ‘blue sea dragon’) feed on the poisonous tentacles of a Porpita porpita, known as a ‘blue button’. At the tips of the blue button’s tentacles are stinging cells called nematocysts, but the venom doesn’t deter the sea swallow. Instead, once the sea swallow eats the blue button’s poison, it stores the venom in the tips of its own feather-like fingers called papillae. Predators should think before biting the sea swallow, as the poison can kill them in seconds. If you come across either of these creatures washed ashore, don’t touch! While the stings aren’t deadly to humans, they can cause skin irritation. You can’t tell from this picture, but these sea creatures are tiny (a few centimetres long) and get around by floating on ocean currents.