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 yellow bioluminescent ring on this female octopus ( Bolitaena pygmaea ) may attract mates. Bioluminescence is an important adaptation that helps many deep sea animals survive in their dark world...
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...
Many jellyfish in the class Hydrozoa, such as this hydromedusa Aglantha digitale , are transparent and easily overlooked. Learn more about hydrozoan jellies and other jellyfish , and see more...
Like octopods and cuttlefishes, giant squid have eight arms. But they use their two much longer feeding tentacles to seize prey. The tentacles have powerful suckers at the ends. More about the giant...
Atolla tenella , a midwater scyphomedusa , as seen under a microscope. View the “Under Arctic Ice” photo essay to learn more.
The yeti crab ( Kiwa hirsuta ), an unusual, hairy crab with no eyes, was discovered in 2005 on a hydrothermal vent near Easter Island. It represents not only a new species but also a new genus— Kiwa...
Home is where the hull is: Since the dawn of seafaring, humankind has had to deal with pesky creatures, such as barnacles, that “foul” ship hulls and boat propellers like this one. Find out more 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...
This jelly’s red color provides camouflage in the deep ocean. Red light rarely reaches those depths, and most deep-sea animals have lost the ability to see red. The long, complex tentacles of this...
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...
Deep sea animals have to live in a very cold, dark, and high-pressure environment where they can't see a thing! To survive there, they've evolved some very strange adapations. Some make their own...
The ocean is home to many moms of all shapes and sizes: from charismatic polar bears and dolphins to small fishes and shrimps and more. Learn about some of the diverse parenting habits of marine moms...
In Antarctica's Southern Ocean swims a beautiful polychaete (bristly worm) called Tomopteris carpenteri , which is adorned with alternating red and transparent bands. The largest species in its genus...
Male fiddler crabs, like this one collected on Moorea, wave their enlarged claw as way of signaling to other crabs, especially during mating season. Learn more about the Island of Moorea in the...
The blue lined octopus may be small, growing to at most 15 cm, but it can be deadly: its venom can cause breathing failure in humans as well as other animals. Turtles can accidentally consume 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...
Anemones are known for serving as homes for Nemo and countless other small fish and invertebrates. But these Cnidarians (in the same phylum as jellyfish and same class as corals ) have a long journey...
This beautiful larval (baby) octopus was collected by scientists from the University of Miami during a research cruise in the Straits of Florida, a narrow channel between the Atlantic and the Gulf of...
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