Best Christmas present! This glaucus washed up by the heavy seas courtesy of the cyclone up north …
Glaucus atlanticus, a nudibranch, floats on the surface of the ocean, along with other members of the “blue brigade“. It can wriggle a bit, as this one was in its pond, but is mostly at the mercy of wind and currents, as are its confederates.
It feeds on the bluebottle, Physalia physalia, and moves the bluebottle’s stinging cells from its stomach into its own tips, so anything trying to eat it will get a mouthful of bluebottle stings. Other nudibranchs do this: see Evolution Happens for a description.
This one was about 3 cm long. The hole on the left side is a reproductive pore. Glaucus is a hermaphrodite.
I don’t see them very often, and this one was a special surprise on Christmas morning. Thanks, Mother Nature!