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Watch as barnacles feed on bioluminescent dinoflagellates. Barnacles are crustaceans (like crabs, shrimps and lobsters) that secrete their shells for protection while living attached to things like rocks, harbors or boat hulls. They feed...
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Depending on whom you talk to, jellyfish are either fascinating, a nuisance, a...
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The ocean is home to a phenomenal diversity of marine organisms. They have...
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This summer, many of you have likely enjoyed feasting on crabs, be they blue,...

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Zombie worms ( Osedax roseus ) eat away at the bones of a dead whale that has fallen to the seafloor in Sagami Bay, Japan. These bizarre worms rely on whale bones for energy and are what scientists call “sexually dimorphic”—the...
What are corals? Corals themselves are animals. But tropical reef-building...
In recent years, blooms of jellyfish, such as these moon jellies ( Aurita...

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Nudibranchs are a kind of sea slug, and their 3000 species are found from the poles to the tropics in both shallow and deep...
Shown here are several deep-sea coral species: From left to right is an unidentified purple octocoral, a small gold acanthorgorgiid octocoral, and a large colony of pink Corallium secundum . Basket...
A sea monster attacks a ship in an illustration for 20,000 Leagues Under the Sea by Jules Verne. The illustration is by publisher and artist Pierre-Jules Hetzel, who is most famous for his drawings...
Riftia tubeworm ( Riftia pachyptila ) colonies grow where hot, mineral-laden water flows out of the seafloor in undersea hot springs—such as the Guymas Basin of the Gulf of California at 2,000 meters...
Many sperm whales stranded on beaches or caught by whalers exhibit telltale circular scars like these. Only one thing could have made them: the strong suckers that line the giant squid’s eight arms...
Chrysaora melanaster , one of the largest jellyfish commonly found in the Arctic, swims underneath the Arctic ice . Its tentacles can stretch to more than 3 meters long and pack a mean sting for...
Acorn barnacles ( Balanus crenatus ) make a home on the carapace of an edible crab ( Cancer pagurus ). Much of the Baltic suffers from eutrophication that leads to oxygen depletion. The algae blooms...
When hoping to discover a pearl, looking inside one of the oysters you slurp may not be the best plan. Food oysters in the family Ostreidae are able to produce pearls, however these tend to be small...
Instead of females, male seahorses carry the developing seahorse embryos in a kangaroo-like pouch. During mating season, the female deposits her eggs into the pouch, and the male fertilizes them...
These Pacific cephalopods illustrate the wide diversity among this group of mollusks. You can learn about a relative, the giant squid ( Architeuthis dux ), in our Giant Squid section.
The Smithsonian's Department of Invertebrate Zoology has a collection of over 57,000 specimens from over 5,700 sites in the Gulf of Mexico, which are now catalogued on Google Earth . Below is a tiny...
With a scientific name that means "the vampire squid from hell," you'd expect the vampire squid ( Vampyroteuthis infernalis ) to be a fearsome predator terrorizing the deep. Despite its demonic look...
You are not alone if you don’t know what forams (short for foraminifera) are, so let’s start with the basics. Simply put, forams are single-celled organisms related to the familiar amoeba that...
All over the world, people have been witnessing gigantic blooms of tens of thousands of jellyfish where once there were only a few. Fishers find them clogging their nets and costing them dearly. In...
This nudibranch has a few tricks up its sleeve: it steals jellyfish tentacles to use as weapons again its own enemies. How does it do this? Many fleshy, tentacle-like growths, called cerata (singular...
This brilliant red octopus ( Benthoctopus sp. ) was photographed at more than 8,800 feet (about 2,700 meters) in Alaminos Canyon in the Gulf of Mexico. See more photos of wild creatures encountered...
The European green crab ( Carcinus maenas ) has spread far beyond its native continent, to waters off North and South America, Asia and Australia. It's a voracious eater and poses a nuisance to...
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 beach...
This forest of Christmas tree worms is a group of polychaete worms that live on tropical coral reefs. See more celebratory ocean creatures in our slideshow!
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