This blog post was prompted by this brilliant Blue Dragon photo sent recently by Debbie Mclean. It looks like a real monster but is really only 2-3 cms long.

Intrigued, we consulted the Australian Geographic’s website to find out about them and other blue things that blow in from the ocean from time to time. Here’s what we found.

Blue Dragons are nudibranch (sea slugs) which swallow a bubble of air so they float and are at the mercy of the wind. They feed on bluebottles and ingest some of the toxin to protect themselves. They may sting you if you handle them but unlike bluebottles often don’t. The blue colour camouflages them from predators below the surface.

Bluebottles (Physalia utriculus) are actually a colony of polyps that act like an individual creature. They are smaller and less venomous than the related Portuguese Man O’ War (Physalia physalis). The parts function individually but cannot survive alone. Bluebottles catch, sting and kill small fish and other marine life with tentacles containing sting cells (nematocysts). The floats can grow to 15 cm but, interestingly, lean either to the left or the right. This stops all of the population (called an armada) being beached at one time.

By-the-wind Sailors are like bluebottles in that they are composed of individual polyps, organised into a single creature. They have sails instead of floats, but the sails like the bluebottle floats are either right or left “handed”. Also, they are prey for the Blue Dragons.