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...
The Boreoatlantic armhook squid ( Gonatus fabricii ) is named for its fabulous (but dangerous) suckers. While most squids have just two rows of suckers lining each arm, armhook squids have four—and...
Flower-like clusters of polyps make up this coral colony. Their pink color comes from the zooxanthellae living inside. More about coral reef ecosystems can be found in our Coral Reefs featured story .
Like it or not, giant squids are related to snails, clams, and even slugs. They are all mollusks and have soft, fleshy bodies. More can be found in the Giant Squid section .
A thicket of white stony coral ( Lophelia pertusa ) shelters a squat lobster (Eumunida picta). This is the typical shape of this widespread species of deep-sea coral. See more pictures of coral in...
White abalones are slow-moving, algae-eating mollusks. Rapid overharvesting since the 1970s has resulted in white abalones becoming the first marine invertebrate listed as endangered on the...
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...
This close-up photo shows the tough, serrated ring around the opening of a giant squid sucker. The ring is made of chitin—the same material that’s in your fingernails. Using suction, the sucker...
The largest of the cuttlefish species, Australian Giant Cuttlefish ( Sepia apama ) delight scientists each year as they gather in masses to spawn in northern Spencer Gulf, northwest of Adelaide in...
Despite the cold and dark environment, soft-bodied animals like anemones abound under the ice. Using their sticky arms, they grab zooplankton, which can be hard to come by during the long winter with...
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...
Sea jellies such as this one in the genus Benthocodon are commonly seen on or near the seafloor in the Monterey Canyon off central California. Some jellies in this genus feed on animals that live in...
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...
What is this bizarre, spiky-looking organism? Hint: it can be found in tropical areas of the Pacific and Indian ocean basins crawling slowly over coral reefs and devouring any living coral polyps...
In 1874, Reverend Moses Harvey of Newfoundland bought a dead giant squid caught by fishermen. More about the giant squid can be found in our Giant Squid featured story .
The dark seafloor beneath the ice is covered with sea stars, urchins and ribbon worms looking for their next meal, which can come from sponges, dead animals that float to the sea floor, or even other...
Discovering new species is an exciting quest, right? Well, some parts are—but after you find a cool-looking organism that you think is a new species, there's a lot more to be done. You have to...
Scientists describe the amazing bioluminescent creatures they encounter as they descend into the deep--siphonophores, ctenophores, and viperfish--in this Smithsonian/History Channel "Deep Ocean...
Ochre seastars ( Pisaster ochraceus ) feed on invertebrates, such as coral and shellfish, like the mussels pictured here. The starfish forces open the shell with suction disks on the underside of its...
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