Beautiful but deadly, the Glaucus atlanticus, commonly known as “the blue dragon”, is not what one would expect of a mere slug. Not only is it visually stunning, it possesses abilities unlike any other creature on Earth.


Appearance: The blue dragon has three pairs of arms, each one shorter than the last as they go further down it’s body. On these arms are single rows of tendrils called cerata which hold stinging cells – there can be up to 84 of these on a single blue dragon. The dorsal side is a silvery gray colour while the ventral side is covered in a light blue. Its feet on the dorsal side have dark blue stripes. The jagged teeth of this mollusk help it to scrape food particles and draw them into its mouth

CLASS: Gastropoda

OTHER NAMES: Sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug, blue ocean slug

1 Though part of the nudibranch family, the blue dragon is vastly different from your average sea slug, and is known to be pelagic, using the ocean currents to carry it along

2 The blue dragon floats upside down for camouflage: Its blue side faces upwards to blend with the blue water, while the downwards facing silver side blends in with the ocean’s surface

4 The immune system of a blue dragon is built to resist the venom of its prey

The male reproductive organ is especially large and hooked


5 All blue dragons are hermaphrodites, meaning they have both male and female reproductive organs

6 When two blue dragons mate, they both produce egg strings. These egg strings lack a hard substrate to attach to, and are often left to float freely in the water or are placed on the remains of their prey until the larvae hatch

During mating, both female reproductive organs will release an egg string containing about 20 eggs

3 They only feed on venomous creatures, often much larger than itself, such as the Portuguese man o‘ war and can deliver a powerful sting to paralyze its prey

7 These little slugs have the amazing ability to swallow the nematocysts of its venomous prey. These venomous cells are stored in the extremities of their cerata, making the blue dragon’s sting pack an even more powerful punch


Read more about the gorgeous blue dragon and the marine sanctuaries it is found in around the world in No. 112 Issue  2/2018 of Scuba Diver magazine

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