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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Zombie worms don’t crave brains: instead they seek bones. The 1 to 3 inch (2 to 7 centimeter) Osedax worms were first discovered living in the bones of a rotting gray whale on the...
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Today’s discoveries about our planet’s biological diversity build upon the...
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Marine parasites may be small in size, but they can be present in very high...
During the summer of 1998, scientists at the Virginia Institute of Marine...

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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 nematocysts. Of course, this...
Census of Marine Life researchers discovered this unusual transparent sea...
Smaller than the head of a pin, this arrow squid (Doryteuthis plei ) embryo...

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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...
Sea butterflies (also called pteropods) are sea snails aptly named: they are shelled marine snails, each with a foot like a wing, that swim in the water column like butterflies. This one, Atlanta...
This ctenophore (a stingless jellyfish-like animal) is native to the east coast of North and South America. In 1982, it was discovered in the Black Sea, where it was transported by ballast water . It...
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 .
The festive Christmas tree worm ( Spirobranchus giganteus ) lives on tropical coral reefs and resembles a fluffy fir tree adorned with ornaments. The multi-functional branch-like appendages are used...
Today’s discoveries about our planet’s biological diversity build upon the research of previous generations of scientists. The Biodiversity Heritage Library (BHL) is a digital library committed to...
A thicket of white stony coral ( Lophelia pertusa ) shelters a squat lobster (Eumunida picta). This is the typical shape of this widespread species of deep-sea coral. See more pictures of coral in...
Can you spot the amphipod ( Phronima atlantica ) in the below photo? She's the transparent lobster-looking animal in the middle, surrounded by her own eggs -- inside a sac that once was the "barrel"...
The over 1,000 species of ribbon worms ( Nemertea ) are mostly found in marine environments (like the Hubrechtia found in a mud flat, in the photo). These worms have both a mouth and an anus (unlike...
In recent years, blooms of jellyfish, such as these moon jellies ( Aurita aurita ) in the Chesapeake Bay, have become more common around the world for a number of different reasons . One result of...
“Upon returning from the reef after a night dive, I swam toward a bright reflection and came eye-to-eye with this beautiful, curious squid," said Charles Viggers, a Nature's Best photographer. Squids...
The giant squid is among the largest invertebrates on Earth, but this deep sea creature has rarely been observed by humans -- alive. Over the centuries, many dead giant squid have washed up on the...
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...
This male dancing fiddler crab ( Uca terpsichores ) has built a sand “hood” at the entrance to his burrow, which he hopes will attract females to his humble abode—as if that big beautiful claw of his...
Two brown and purple nudibranchs ( Risbecia tryoni ), crawling in tandem on a surface encrusted with pink-colored coralline algae. These "sea slugs" live in the tropical Western Pacific Ocean. You...
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...
Named for the radiant blue color on its back and sides, the blue shark ( Prionace glauca ) traverses the world’s temperate and tropical seas. Known for traveling great distances and being a swift...
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...
The sargassum is coated with encrusting organisms, such as bryozoans and hydroids, that use it as a perch to filter feed in the oceanic waters, as well as crustaceans such as thos swimming crab...
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