Glaucus Atlanticus

With the aid of a gas-filled sac in its stomach, Glaucus atlanticus floats at the surface. Due to the location of the gas sac, it floats upside down, where it is carried along by the winds and ocean currents.

It also makes use of countershading: the blue side of their body faces upwards, blending in with the water. The silver/grey side of the sea slug faces downwards, blending in with the ocean when viewed facing upwards underwater.

These sea slugs are pelagic, meaning that they inhabit the upper layers of the open sea. Glaucus atlanticus feed on other pelagic creatures, including the Portuguese man o’ war and other venomous siphonophores (A group of animals that includes the corals and true jellyfish). This sea slug stores stinging nematocysts from its prey within its tissues as protection against predators. Humans handling the slug may receive an extremely painful and potentially fatal sting.