Size – They are small and range from 0.8-1.5 inches (20-40mm)
Blue Sea Slugs are beautiful, dragon-like slugs. They use countershading, similar to a shark, where their blue side faces upwards to blend in with the ocean blue, and their underside is silver/grey to match the reflection of sun on water. They move by floating upside down, using the tension of the water, winds, and current to stay up and moving. These Blue Dragons are able to produce a powerful sting, comparable to a Portuguese man o’ war.
They can be found in most oceans, in temperate and tropical waters. The smaller Glaucus, the Marginatus, is generally most often found in the Indian Ocean and Pacific Ocean, while the Atlanticus is found in the Atlantic. They prefer to dwell in the open ocean, but occasionally wash upon shore.
These Blue Ocean Slugs are well known to prey on Portuguese man o’ wars, sea rafts (vellelas,) and blue buttons. Their immunity to venom allows them to consume chunks of their prey, and they can even store venomous nematocysts to use against predators or future prey.
They float upside down due to the gas sac in their stomach. Blue Dragons also have a more venomous, painful, sting than a man o’ war. Don’t pick these guys up.. Or you may find yourself feeling nauseous, in pain, and even vomiting.
The Blue Sea Slug is a Slug of many names; blue sea dragon, blue angel, blue glaucus, dragon slug, blue dragon, and blue ocean slug to name a few.
The genus Glaucus are the only member in the family Glaucidae.
They belong to the superfamily Aeolidioidea who are aeolid Nudibranches.
There are five species of Glaucus:
- Glaucus atlanticus – Atlantic Ocean
- Glaucus bennettae – South Pacific
- Glaucus mcfarlanei – North Pacific
- Glaucus marginatus – Indo-Pacific
- Glaucus thompsoni – North Pacific