Invertebrates

Animals without backbones make up a huge percentage of the ocean’s biodiversity. They aren’t just small (like pteropods) or squishy (like jellyfish); the giant squid and corals that build huge reefs are also invertebrates.

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Marine parasites may be small in size, but they can be present in very high numbers and put together can weigh even more than all the top predators in an estuary or bay ecosystem!...
During the summer of 1998, scientists at the Virginia Institute of Marine...
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The blanket octopus can rip a poisonous tentacle from a Portuguese man-o-war...
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Hyperiid amphipods are small crustaceans related to sand fleas and distantly...

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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...
What are corals? Corals themselves are animals. But tropical reef-building...

DIVE DEEPER

Jellyfish and comb jellies are gelatinous animals that drift through the ocean's water column around the world. They are...
This beautiful spider conch ( Lambis chiragra ) was collected by Census of Marine Life scientists conducting research near China.
Ocean scientists discovered this 1.5-m (5-ft) tall yellow bamboo coral in 2007 off the coast of Hawaii in 1,459 m (4,787 ft) of water. It is thought to represent a new genus. Learn about more deep-...
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 .
A small horseshoe crab ( Limulus polyphemus ) rests on seaweed in Stage Harbor, Massachusetts. Atlantic horseshoe crabs can be found along the coast of North America from the Yucatán Peninsula to...
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...
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...
For a long time, scientists thought that some small tentacled fossils were early ancestors of jellyfish. But a new study has found that these ancient animals are actually related to an entirely...
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...
The blanket octopus can rip a poisonous tentacle from a Portuguese man-o-war and wield it like a sword to ward off enemies as it soars through the ocean trailing its webbed cloak behind it...
A longshoreman stands in front of a large pile of oyster shells on waterfront pier in Atlantic City in 1910. Back then, oysters were incredibly abundant. In the late 1800s, fishermen pulled in 10...
One of the most common inhabitants of the sargassum community, the shrimp Latreutes fucorum (Hippolytidae) is perfectly colored to hide on the leaf-like blades. Off the coast of Belize, Smithsonian...
This close-up view of salps, which have aggregated together into a long chain, have brilliant red guts from eating red plankton. They were observed by researchers with the Census of Marine...
This octopod is sometimes called a “Dumbo” octopod because its fins resemble the ears of Disney’s Dumbo the elephant. The video was recorded in 2003 on the Mid-Atlantic Ridge by the Russian manned...
This pair of sea butterflies ( Limacina helicina ) flutter not far from the ocean's surface in the Arctic. Sea butterflies are a type of sea snail, but instead of dragging themselves around the...
The lion’s mane jellyfish ( Cyanea capillata ) is the largest among the jelly species, with the largest known specimen stretching across 120 feet (36.5 meters) from its top to the bottom of its...
These baby olive ridleys ( Lepidochelys olivacea ) will eventually provide a home to crustaceans, mollusks, and other epibionts. That's according to a survey of epibionts living on mature, nesting...
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