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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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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 humans.
A sea monster attacks a ship in an illustration for 20,000 Leagues Under the...
Many sperm whales stranded on beaches or caught by whalers exhibit telltale...

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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...
Inside the giant squid's sharp beak is a tongue-like organ called the radula (shown in yellow). Covered with rows of tiny teeth, it rams bite size pieces of food down the squid's throat. The pieces...
In this photo of a shallow coral reef in the Pacific there are three species of forams . On the left, Peneroplis planatus . In the center, Amphistegina lessonii . And on the right, Laevipeneroplis sp...
A mangrove tree crab ( Aratus pisonii ) clings to a leaf near the Smithsonian Institution’s marine laboratory on Galeta Island, Panama, part of the Smithsonian Tropical Research Institute . During...
The Baltic is a brackish sea, a unique combination of freshwater from rivers in the surrounding countries and salt water from the ocean. The low salinity levels are one of the factors that determine...
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...
Squids come in a wide range of sizes but despite differences in size and shape, all work basically the same way inside. More about the giant squid can be found in the Giant Squid section .
When they get larger, Portunus sayi are formidable predators, quick to consume any smaller animal that comes within reach. Fish, other crustaceans, and even smaller members of their own species are...
The veined octopus ( Amphioctopus marginatus ), also known as the coconut octopus, has a skill beyond other cephalopods: it hides under animal and coconut shells, dragging them along the seafloor for...
There aren't any mummies or zombies buried under the seafloor: instead the ocean has its own terror from below, the bobbit worm ( Eunice aphroditois ). A couple inches wide and up to ten feet long,...
Seahorse couples, such as this pair of thorny seahorses ( Hippocampus histrix ) , greet each other every morning with a unique dance that sometimes involves changing color. The couple promenades and...
Giant anemone. More about mangrove ecosystems can be found in the Mangroves section .
The giant squid is among the largest invertebrates on Earth, but this deep sea creature has rarely been observed by humans -- alive. Over the centuries, many dead giant squid have washed up on the...
Sea stars ( Odontaster validus ) and sea urchins ( Sterechinus neumayeri ) spread over an algae-covered seafloor off the coast of Antarctica. These two species are often found living in association...
Found in the icy waters of the Arctic , Comb Jellies, or ctenophores like this one, of the Aulacoctena genus, are poorly known animals. With extremely fragile bodies, they are difficult to capture...
How do you get two dead Giant Squid the size of a school bus from a fishing boat in Spain to Smithsonian’s National Museum of Natural History in Washington, D.C.? Call in the U.S. Navy! In this...
In 2012, the long-elusive giant squid was finally filmed live in its natural habitat. The squid was found by placing glowing lures outside of a submersible to mimic jellyfish, which typically...
This photo shows just a small part of the cephalopod collection at the Smithsonian's National Museum of Natural History. Shown here is Dr. Clyde Roper , a zoologist and squid expert. More about the...
A male mudflat fiddler crab ( Uca rapax ) waves its huge claw to impress females and threaten competitors. Only the males have the large claw. When the tide is high, fiddler crabs retreat to their...
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