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...
A sea monster attacks a ship in an illustration for 20,000 Leagues Under the Sea by Jules Verne. The illustration is by publisher and artist Pierre-Jules Hetzel, who is most famous for his drawings...
Winner of the ‘best camouflage’ contest, the nudibranch Scyllaea pelagica (Scyllaeidae) is usually betrayed only by its motion. Along it’s back, the sea slug has growths called papillae that help its...
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"...
Dr. Clyde Roper prepares to dive thousands of feet to a giant squid habitat off the coast of New Zealand in a one-person submersible. More about the giant squid can be found in our Giant Squid...
Species of deep-sea gold coral, or Gerardia , often have a tree-like shape, as you can see in this specimen. See more pictures of coral in our Deep-sea Corals article.
A “pink meanie” jellyfish ( Drymonema larsoni )—a species found in the Gulf of Mexico and the Caribbean—feeds on a moon jelly ( Aurelia ). Dr. Keith Bayha from the Dauphin Island Sea Lab and Dr...
The shrimp shown in this picture is a lot smaller then it looks- most adult anemone shrimp will only grow to about ½-1 inches long. Anemone shrimp ( Periclimenes inornatus ), reside as the name...
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...
Jellyfish and comb jellies are gelatinous animals that drift through the ocean's water column around the world. They are both beautiful—the jellyfish with their pulsating bells and long, trailing...
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 “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...
Humans have long been captivated by what we now call the giant squid ( Architeuthis ). This image gallery gives a glimpe into our fascination with the animal. For a long time, people saw mysterious...
This nudibranch, or shell-less marine snail, is making a comeback to a location it hasn't been to in years along the California coast. First discovered off the coast of Southern California in 1902,...
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 deep sea floor,...
A huge colony of brittlestars (likely Ophiacantha rosea ) covers the peak of a seamount in the deep ocean. What’s the attraction? Food! Their arms reach out for tiny food particles carried by the...
Collect, sort, identify, photograph, sample, record. Repeat a couple thousand times. This is what the students and researchers have been doing as the Indonesian Biodiversity Research Center (IBRC)...
Nudibranchs are a kind of sea slug, and their 3000 species are found from the poles to the tropics in both shallow and deep water. Though they often only reach two centimeters in length, they are...
What reef animal comes in a rainbow of crazy colors, can throw out its stomach to immobilize predators, then creep away and regrow a brand-new stomach? It’s the sea cucumber, prized as a gastronomic...
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