Blue Dragon Glaucus Atlanticus Facts: They Make The Prey’s Venom Their Own

Did you know that there’s a sea slug that is so powerful, it can take down creatures much larger than itself? Meet the blue dragon sea slug – a tiny, but mighty marine predator that reigns supreme in the ocean. From its vivid blue coloration to its unique feeding habits, the Blue Dragon is a creature of mystery and intrigue. Let’s uncover some of the most fascinating facts about them in the article below!

Blue dragon sea slug
Scientific name: Glaucus atlanticus
Phylum: Mollusca
Class: Gastropoda
Order: Nudibranchia
Family: Glaucidae Genus: Glaucus

1. Blue Dragons Camouflage With Color

The glaucus atlanticus or the blue dragon sea slug is not really a dragon. It’s a type of sea slug, just like the sea bunny or leaf sheep. This is a small creature with a size of 3 cm in length and weighs just 3 – 100 g.

To protect itself, this species uses a countershading technique. It displays a silvery grey hue on its dorsal side and a dark and light blue coloration on its ventral side. Its head is adorned with dark blue stripes.

The blue dragon sea slug is floating

This color scheme is not only visually appealing but also serves a practical purpose, as it helps the dragon camouflage in its environment. Its blue upward-facing side helps it blend in with the blue of the sea, whereas its silver downward-facing side helps it blend in with the sparkling surface of the water. With this coat, the blue dragon sea slug looks almost undetectable to its predators from both sides.

In addition, the blue color may also aid in the reflection of damaging UV rays. However, just like other blue animals, its blue color is just the refraction of light. You can see the list of other exclusive blue creatures here.

The flattened, tapered body of the Glaucus is adorned with six appendages that spread out into 84 finger-like structures known as cerata. When catching food or when threatened, this sea slug will use these long and thin cerata to sting. Additionally, the Glaucus possesses radular teeth that resemble the serrated edge of a knife.

In 1777, Forster – a scientist – discovered the blue dragon sea creature. This species was named after the Greek sea god Glaucus who, according to legend, achieved immortality by consuming a magical herb.

2. Blue dragon Glaucus atlanticus Habitat

Blue dragon Glaucus atlanticus lives in oceans worldwide, inhabiting waters in the Indian, Pacific, and Atlantic Oceans.

Their habitat, however, appears to be growing. These blue dragon slugs are reported to be observed in unusual locations like off the coast of Taiwan, near Mozambique, in European waters, South Padre Island in Texas, on the east and south coasts of South Africa, and along Australia’s east coast.

This shift in habitat may be due to a combination of factors, including warming oceans and increased storm activity. This causes them to float further or into other shores. Another possible factor could be cyclical changes in the population of their main prey.

Fun fact:
The atlanticus glaucus is called by different names, including blue sea slug, blue angel, blue glaucus, blue sea dragon, blue ocean slug, dragon slug, and sea swallow.

3. They like to gather together

As you can see, the blue dragon Glaucus atlanticus does not swim in the traditional sense. To retain buoyancy, they take in air bubbles and hold them in a gas-filled sac, allowing water currents and winds to transport them away. They typically love to float upside down on the ocean’s surface, occasionally drifting to the ocean floor’s sandy bottom.

Sometimes, the sea slugs can move on their own instead of going with the flow. They use the millions of tiny hairs on their fleshy foot to propel themselves.

These nudibranch blue dragons also enjoy floating in groups, or “fleets,” which creates better opportunities to eat and reproduce. However, moving in groups can get them pushed to the shore by strong ocean winds. They can get stuck there and die if they are not dragged back to the waters by the tide.

When caught in waves and pushed toward the beach, blue dragon sea slugs defend themselves by curling into balls.

4. They eat toxic species

Despite its cute appearance, this diminutive creature is not a harmless species. Instead of floating around eating plankton and small fish, they look for prey several times their own size.

Their diet includes the common purple snail (aka violet snail), the blue button, and the by-the-wind sailor velella. Their favorite food is a Portuguese Man O’War, which is a jellyfish-like organism with long tentacles.

As you may know that man-of-wars have venomous tentacles that can kill other small species easily. However, this means nothing to the blue dragon glaucus atlanticus. The mucus layer and hard disks inside these sea slugs’ skin protect them from the sting. To eat the prey, they use their radular teeth to chew the prey’s tentacles. In addition to these prey, little blue sea dragons have been known to consume their own kind.

The loggerhead turtle is their main predator.

5. They take venom from their prey

Despite their tiny size, the blue dragon Glaucus atlanticus is quite dangerous. Besides the colors to camouflage, these creatures have another defense mechanism – their severe sting.

The slug isn’t venomous entirely by itself, it takes it from its stinging prey. When feeding on venomous prey like siphonophores or Portuguese man o’ wars, this blue sea slug gathers its toxic stinging nematocysts and stores them in the tips of its extremities.

The blue dragon’s venom is highly condensed, which delivers an even stronger sting than that of the man-of-wars. Even after the tiny blue sea dragon dies, its venom remains active. So do not touch or step on it if it becomes trapped on the beach.

If you get stung, their venom can cause serious symptoms like vomiting, nausea, pain, etc. The sting can last up to an hour, and in rare cases, it can cause blisters and scarring. In severe cases, the blue dragon’s concentrated toxin can kill you, particularly for individuals with severe allergic reactions. Therefore, it is essential to avoid picking up the deadly blue dragon sea slug, despite its beautiful appearance.

A group of blue dragon sea slug is eating man o wars

6. Life cycle

Blue dragons, like all sea slugs, need a mate to produce viable eggs despite having both female and male reproductive organs.

To find a mate, they simply float along until they encounter another slug. Because they can hurt their partner with their venomous sting, the slugs own long and curved S-shape bends in their penises.

Two blue dragon sea slugs are mating/Cre: on pic

After mating, they separate and lay strings of 12 to 20 eggs on floating items such as debris, their prey carcasses, or any other floating object they come across. The eggs hatch independently, and the offspring remain afloat until their air sacs form. Their lifespan is about one month to a year.

7. They are endangered

Like many marine creatures, the blue glaucus faces numerous threats to its survival. Due to their popularity on the internet, the rare blue sea dragons have become a popular exotic pet. Unfortunately, it is impractical to keep these creatures due to their dietary requirements. They frequently starve to death.

Climate change poses another significant danger. Ocean acidification caused by rising CO2 levels reduces the food sources of their main prey – man-of-war. This indirectly affects the population of the blue dragon sea slugs. Pollution can also kill these species.



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We are passionate animal enthusiasts with over a decade of experience studying animals. With a degree in zoology and conservation biology, we've contributed to various research and conservation projects. We're excited to bring you engaging content that highlights the wonders of the animal kingdom. We aim to inspire others to appreciate and protect wildlife through informative content grounded in expertise and passion. Join us as we delve into the captivating world of animals and discover the incredible stories they have to tell.

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