Blue Glaucus | Oceana
Home / Blue Glaucus

Marine Life Encyclopedia

Corals and Other Invertebrates

Blue Glaucus

Glaucus atlanticus

Distribution

Atlantic, Pacific and Indian Oceans

ECOSYSTEM/HABITAT

Open ocean

FEEDING HABITS

Foraging predator

TAXONOMY

Order Nudibranchia, Family Glaucidae

The blue glaucus, which is also called the blue dragon, sea swallow, or blue angel, is a brightly colored nudibranch, commonly known as sea slugs.  Found throughout the Atlantic, Pacific, and Indian Oceans in tropical and subtropical waters, the blue glaucus grows up to 1.2 inches (3 cm) long. These tiny sea slugs spend most of their lives floating upside-down at the surface, staying afloat by storing air bubbles in their stomach.

The bright colors of the blue glaucus are an example of a phenomenon called countershading. Its bright blue underside helps the blue glaucus blend into the water’s surface while its grayish backside helps it blend into the ocean when spotted from below, camouflaging it from both flying and swimming predators while floating in open water. But these nudibranchs don’t just depend on camouflage for protection. By feeding on venomous prey, including Portuguese Man-O’-war, and ingesting their prey’s stinging cells, the blue glaucus becomes toxic itself. A group of blue glaucuses floating together is called a “blue fleet.” These “blue fleets” often wash ashore and can sting people swimming in the water.

The blue glaucus is a simultaneous hermaphrodite — each individual has both male and female reproductive organs. After a pair mates, they will lay a string of about 16 eggs in the water which take about three days to hatch into larvae. Due to the blue glaucus’s small size and its wide range around the world, little is known about its conservation status.

Get Involved

Donate Today

SUPPORT OUR WORK TO PROTECT THE OCEANS BY GIVING TODAY

With the support of more than 1 million activists like you, we have already protected nearly 4 million square miles of ocean.

Donate Now

TAKE ACTION NOW

Support policy change for the oceans

Decision-makers need to hear from ocean lovers like you. Make your voice heard!

Sign Now

VISIT OUR ADOPTION CENTER

SYMBOLICALLY ADOPT AN ANIMAL TODAY

Visit our online store to see all the ocean animals you can symbolically adopt, either for yourself or as a gift for someone else.

Shop Today

DOWNLOAD OCEAN ACTIVITIES

HELP KIDS DISCOVER OUR BLUE PLANET

Our free KELP (Kids Environmental Lesson Plans) empower children to learn about and protect our oceans!

Learn More

FEATURED CAMPAIGN

Save the Oceans, Feed the World

We are restoring the world’s wild fish populations to serve as a sustainable source of protein for people.

Learn More

More CAMPAIGNs

Protect Habitat

Bycatch

Plastics

View All

CONTACT

Oceana International Headquarters
1025 Connecticut Avenue, Suite 200
Washington, DC 20036 USA

General Inquiries
+1(202)-833-3900
info@oceana.org

Donation Inquiries
+1(202)-996-7174
wavemaker@oceana.org

Press Inquiries
+1(202)-833-3900
press@oceana.org

OCEANA'S EFFICIENCY

BECOME A WAVEMAKER

Sign up today to get weekly updates and action alerts from Oceana.

SHOW YOUR SUPPORT WITH A DONATION

We have already protected nearly 4 million square miles of ocean and innumerable sea life - but there is still more to be done.

Donate Now

QUICK LINKS: