Invertebrates

Animals without backbones make up a huge percentage of the ocean’s biodiversity. They aren’t just small (like pteropods) or squishy (like jellyfish); the giant squid and corals that build huge reefs are also invertebrates.

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A reddish-orange nudibranch.

DIVE DEEPER

A Collage of Nudibranch Colors

Nudibranchs are a kind of sea slug, and their 3000 species are found from the poles to the tropics in both shallow and deep...
green and red pom poms adorn a decorator crab

Happy Crabby Holidays

Decorator crabs typically adorn themselves with a variety of sea sponges, tufts of algae and other bits and pieces of detritus. In this case researchers provided the crabs with red polyester pom-poms. Credit: University...
Venomous Box Jelly from South Carolina

Pinning Down the Jellyfish

Credit: Bastian Bentlage Depending on whom you talk to, jellyfish are either fascinating, a nuisance, a toxic menace, or some combination of the above. Jellyfish plop into the media spotlight when their presence causes...
Coral Spawning by Moonlight

A Tale of Sex and Stress in the Ocean

A coral has just spawned. Each of the hundreds of polyps releases a small pink bundle of sperm and eggs. Credit: Raphael Williams Welcome to Citizens of the Sea , a new blog series...
Horseshoe Crab in Stage Harbor, Massachusetts

This Flu Season, Thank a Horseshoe Crab

A small horseshoe crab rests on seaweed in Stage Harbor, Massachusetts. Credit: © Luke Robinson (Creative Commons via Flickr) Fever. Aching muscles. Coughing. Sniffling. It’s flu season . Have you had your shot? If...

Hydrothermal Vent Creatures

Travel to a world of perpetual night--the deep ocean hydrothermal vents near the Galapagos Rift where life thrives around superheated water spewing from deep inside the Earth. Discovered only in 1977, hydrothermal vents are...
A screenshot of some of Smithsonian's marine story windows in Google Earth

What Lives in the Gulf of Mexico? Exploring Marine Collections on Google Earth

When he was 10 years old, Stephen Cairns lived in Cuba where he kept a collection of butterflies and sea shells. When his family moved to Louisiana, he could bring only one of the...
Common cuttlefish

So You Think You're Smarter Than a Cephalopod?

Like other cephalopods, the common cuttlefish ( Sepia officials Linnaeus, 1758) possesses serious brain power. Credit: Hans Hillewaert, WoRMS for SMEBD The blanket octopus can rip a poisonous tentacle from a Portuguese man-o-war and...
A zoomed-in image of the crown-of-thorns sea star.

A Plague of Sea Stars

Scientists have been studying why populations of crown-of-thorns sea stars ( Acanthaster planci ) have mushroomed in recent decades. Coral reefs can suffer when the sea star's numbers explode; the echinoderm has a healthy...

The Dumbo Octopus: An Underwater Dance

This short video takes you two hundred miles off the coast of Oregon and some 6,600 feet below the water's surface to observe the Dumbo octopus ( Grimpoteuthis bathynectes ). Little is known about...
Juvenile plane-head filefish

A World Adrift: Life in the Sargassum

The open ocean is surprisingly barren to the naked eye. Every now and again you will encounter a school of fish and their attendant predators, but most of the life that you find is...

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