Invertebrates

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In a decade long project, which ended in October 2010, scientists with the Census of Marine Life traveled the world cataloging the ocean’s life forms. From Australia to China to the Gulf of Mexico...
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From the giant squid to microscopic squid babies, squids are beautiful and...
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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When they get larger, Portunus sayi are formidable predators, quick to consume any smaller animal that comes within reach. Fish, other crustaceans, and even smaller members of their own species are not safe from this hungry...
A huge colony of brittlestars (likely Ophiacantha rosea ) covers the peak of...
This copepod Calanus hyperboreus (up to 7mm in length) lives in the Arctic...

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Coral reefs are the most diverse of all marine ecosystems. They teem with life, with perhaps one quarter of all ocean...
This swimming crab ( Liocarcinus holsatus ) has a parasitic barnacle rooted in its reproductive system. This invasion cuts off all reproduction for an infected crab and can even cause a male crab to...
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...
This copepod Calanus hyperboreus (up to 7mm in length) lives in the Arctic , usually within 500 meters of the surface. To survive the cold Arctic winters, Calanus hyperboreus builds up dense fat (...
This is the first photograph of a live giant squid ( Architeuthis ) in its natural habitat. It was taken in 2004 by two Japanese researchers who had suspended a long line from their research vessel...
Talk about an investment! This octopus mom protected her brood of about 160 eggs for 4.5 years for the longest ever recorded brooding time of any animal. She was first observed by scientists from the...
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...
Watch a Discovery video on Smithsonian squid expert Clyde Roper’s search for giant squid in Kaikoura Canyon off the coast of New Zealand. More about giant squid can be found in our Giant Squid...
This tan urchin, Conolampas sigsbei , is one of only two known deep-sea urchins that cover their tops with small rocks and shells. Many shallow species cover themselves for reasons that have been...
Staghorn (seen here) and elkhorn corals are listed as Threatened under the U.S. Endangered Specis Act, as their numbers have fallen catastrophically due to disease. Listed in 2006, they were the only...
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...
Alaska’s pristine coastline is ripe for an influx of invasive marine species such as the European green crab and the rough periwinkle (an Atlantic sea snail), warns a new study by a team of...
The larger of two giant squids on display in the Smithsonian's Sant Ocean Hall , this female was caught in a fisherman's net off the coast of Spain in 2005. It was probably 2-3 years old and, when...
Like other cephalopods, the common cuttlefish ( Sepia officials ) is no dummy. But while octopuses are quick to learn manual tasks like opening jars, cuttlefish have a different skillset: the social...
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...
In this close-up photo, you can actually see the photosynthetic algae, or zooxanthellae, living inside a tiny coral polyp. Look for the brownish-green specks in the colorless polyp. Corals depend on...
Throughout their lifecycle, jellyfish take on two different body forms: medusa and polyps. Polyps can reproduce asexually by budding, while medusae spawn eggs and sperm to reproduce sexually. Learn...
This brightly colored squat lobster collected in Moorea is a common find among the coral heads. Although called lobsters, this group of crustaceans is more closely related to hermit crabs than to...
It's a pygmy seahorse ( Hippocampus bargibanti ), found in Indonesia's biodiverse Coral Triangle and one of the smallest seahorse species in the world! They can change colors like a chameleon to...
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