Invertebrates

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From the giant squid to microscopic squid babies, squids are beautiful and fascinating. As cephalopods, the same family as octopuses and cuttlefish, they have no bones, and swim head-first through the water with their...
Since summer 2013, starfish along both coasts of the United States have been...
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Tiny plant-like organisms called zooxanthellae live in the tissues of many...
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I have been at the Smithsonian’s National Museum of Natural History since 1966...

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Census of Marine Life researchers discovered this unusual transparent sea cucumber ( Enypniastes sp.) in the Gulf of Mexico at 2,750 meters depth. It creeps forward on its tentacles pretty slowly, at around 2 centimeters per...
Smaller than the head of a pin, this arrow squid (Doryteuthis plei ) embryo...
Anemones are known for serving as homes for Nemo and countless other small...

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Jellyfish and comb jellies are gelatinous animals that drift through the ocean's water column around the world. They are...
A “pink meanie” jellyfish ( Drymonema larsoni )—a species found in the Gulf of Mexico and the Caribbean—feeds on a moon jelly ( Aurelia ). Dr. Keith Bayha from the Dauphin Island Sea Lab and Dr...
A blue cod and sea pens , a unique type of cnidarian , speckle the seafloor in New Zealand's Fiordland region.You can see more beautiful underwater photos from Brian Skerry in his image gallery .
This bearded fireworm ( Hermodice carunculata ) must have a strong stomach -- it’s sucking on fire coral ( Millepora sp. ), which would give the unlucky snorkeler a nasty sting. Encountered in St...
Editor's Note: See more information and details about the organisms displayed in the slideshow here . Researchers who come to Curaçao to take part in DROP ( Deep Reef Observation Project ) aren’t...
A mass of white muscle the size of a softball surrounds the dark brown beak of a giant squid. Learn more about this animal's oversized anatomy in our Giant Squid section .
New, white growth emerges from a living deep-sea coral sample that was stained pink, enabling ocean scientists to measure its coral growth rate. Find out more about how ocean scientists study deep-...
Hyperiid amphipods are small crustaceans related to sand fleas and distantly related to shrimp. They range in size from very tiny to more than 7 inches long, and are found at all depths of the ocean...
This sea potato ( Echinocardium cordatum ) looks similar to its root vegetable namesake, but it's a sea urchin! The spines on this urchin are more hair-like than the spikes seen on some more commonly...
Polarized sunglasses have become the norm for humans when they want to filter out the strong glare from the sunlight bouncing off of water in a horizontal direction. But how do animals do that live...
Dead man’s fingers ( Alcyonium digitatum ) are soft corals named for their appendage-like appearance when thrown ashore by storms. The finger-like clumps of coral polyps come in various shades of...
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.
Smithsonian Zoologist Dr. Clyde Roper , the world's foremost authority on giant squid, explores the squid collection at the National Museum of Natural History. He is passionate about giant squid and...
During the 2012 field season of the Deep Reef Observation Project (DROP) in Curaçao, Smithsonian scientists collected many specimens with the help of the Curasub . Prospective new species were caught...
These newly hatched arrow squid larvae ( Doryteuthis plei ) are each tinier than the head a pin. Free from their yolk sac, they will drift with the current out to sea as zooplankton. Many animals eat...
The shrimp shown in this picture is a lot smaller then it looks- most adult anemone shrimp will only grow to about ½-1 inches long. Anemone shrimp ( Periclimenes inornatus ), reside as the name...
Giant squid have the largest eye in the animal kingdom. At up to 10 inches in diameter, people often describe it as the size of a dinner plate -- or, in other words, as big as a human head. Here,...
This specimen of the deep-sea coral Desmophyllum dianthus shows the visible bands that help marine scientists learn how ocean conditions changed over time. By looking at the thickness of each band,...
Small amphipods, the blue bug-like creatures, can be seen here catching a ride on this enormous sea spider as it makes its way across the bottom. Many Antarctic creatures, like the dinner-plate-sized...
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