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...
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,...
Since summer 2013, starfish along both coasts of the United States have been dying in large numbers—and not gracefully. As their tissues collapse, the starfish (also called sea stars) start to look...
Bivalves brought up in a box corer from the deep Arctic seafloor.
This bivalve mollusk is native to the Caspian Sea, lagoons of the Black Sea, and their inflowing rivers. It lives in fresh and brackish water and cannot tolerate full seawater. In the 18th and 19th...
Another common species of sargassum shrimp, Leander tenuicornis (Palaemonidae), can be spotted by its long transparent claws or "chelae". Very similar shrimp are found in near shore habitats all...
This close-up photo of a right whale's head shows dozens of hitchhikers—tiny crustaceans known as whale lice, or cyamid amphipods. They live on the rough patches of skin (known as callosities) on...
Two California market squids ( Loligo opalescens ) mate in the waters off of California's Channel Islands. While spawning, the male's arms blush red as he embraces the female, a warning to other...
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...
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...
Seahorses range in size—from as small as a pine nut to as large as a banana. The largest seahorse species (pictured here) is Hippocampus abdominalis , or the big-bellied seahorse, which can reach...
The open ocean is surprisingly barren to the naked eye. Every now and again you will encounter a school of fish and their attendant predators, but most of the life that you find is gathered around...
Lanceola clausi , the bull-dog amphipod , another rare deep-water species captured below 1000 meters (3281 feet) with the multinet . View the “Under Arctic Ice” photo essay to learn more.
Sample the surprising diversity of deep-sea corals. See some of the ways they differ in color, shape, and size. Explore more in the multimedia feature " Coral Gardens of the Deep Sea ."
Sea stars are important members of marine ecosystems, especially in the tropics. We may think of tropical coral reefs as being home mainly to fish and corals, but in fact these habitats are home to a...
Many expeditions in the Arctic reveal new species, such as this jellyfi sh Bathykorus bouilloni , which, strangely, has only four tentacles! Dr. Kevin Raskoff from California State University,...
In a 2011 study published in the Bulletin of the Peabody Museum of Natural History , researchers documented a number of different organisms living on olive ridley and green turtles in the Pacific. Of...
Mangrove roots provide support for filter-feeders like sponges, mussels, oysters, and barnacles. These play an important role in keeping the water clear. More about mangroves can be found in our...
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,...
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