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Depending on whom you talk to, jellyfish are either fascinating, a nuisance, a toxic menace, or some combination of the above. Jellyfish plop into the media spotlight when their presence causes beach closures, or...
The ocean is home to a phenomenal diversity of marine organisms. They have...
This summer, many of you have likely enjoyed feasting on crabs, be they blue,...
Zombie worms don’t crave brains: instead they seek bones. The 1 to 3 inch (2 to...

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The blue crab ( Callinectes sapidus ) is one of the most important commercial species in the United States, especially in the Chesapeake Bay region on the Mid-Atlantic coast. Its populations are affected by local water quality,...
Like this ctenophore ( Aulococtena acuminata ), many animals that live in...
Sponges are animals that eat tiny food particles as they pump water through...

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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...

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Nudibranchs are mollusks that have evolved from shelled ancestors. Like the reddish-orange Coryphella verrucosa shown here, they're often noted for their vibrant colors and striking forms. View other...
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...
The mauve stinger’s ( Pelagia noctiluca ) name in German means “night light,” referring to the jelly’s reddish coloring and its bioluminescence, the display of light by a living creature. Unlike a...
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 whitish spots on this fish are individual parasitic trematode worms. Trematodes have complicated life cycles that usually involve multiple hosts -- often starting in a snail and then moving on to...
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...
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...
Comb jellies (such as this Bolinopsis species) are named for their combs: the rows of cilia lining their bodies that propel them through the ocean. Read more about jellyfish and comb jellies .
This giant isopod (a crustacean related to shrimps and crabs) was collected from the cold, deep waters of the Gulf of Mexico in 2006. Scientists believe that it is one of about nine species in the...
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...
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...
Octopuses are colorblind, but manage to blend into the background seamlessly—or stand out in bright color to startle their enemies. So how do they do it? That's the question Roger Hanlon of the...
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...
The “Hyperbolic Crochet Coral Reef,” a unique exhibition and thought-provoking fusion of science, conservation, mathematics, and art, is on display in Washington, D.C., at the Smithsonian’s National...
Like its terrestrial namesake, the Venus fly-trap anemone ( Actinoscyphia sp.) sits quietly and waits for food to drift into its outstretched tentacles, which are lined with stinging harpoons called...
These two nautiluses ( Nautilus belauensis ) are pictured off the coast of Palau in the Pacific Ocean. There are six living species of nautilus who live in chambered shells. As they get bigger, they...
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...
The toothy goby or common ghost goby ( Pleurosicya mossambica ) lives among soft corals and sponges in the Indo-Pacific ocean. The relationship it has with its host is commensal , which means the...
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