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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During the summer of 1998, scientists at the Virginia Institute of Marine Science made a series of disturbing discoveries in the Chesapeake Bay. In June, they collected an unusual specimen: a single marine snail...
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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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Bioluminescence is one of the more captivating adaptations that have evolved in...

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Smaller than the head of a pin, this arrow squid (Doryteuthis plei ) embryo looks like a miniature adult and is almost ready to hatch! Depending on the squid species, the development from a fertilized egg to a nearly-hatched...
What are corals? Corals themselves are animals. But tropical reef-building...
In recent years, blooms of jellyfish, such as these moon jellies ( Aurita...

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Giant squid live up to their name: the largest giant squid ever recorded by scientists was almost 43 feet (13 meters) long,...
Seahorses are the only fish species that can hold your hand! Unlike most fish that use their tails for swimming, seahorses, such as this longsnout seahorse ( Hippocampus reidi ), use their monkey-...
When I set out to write a book about mollusks (called Spirals in Time ), I wasn't quite prepared for just how many animals I would get to know. There are somewhere between 100,000 and 200,000 mollusk...
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...
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...
Most scuba divers scour coral reefs looking for colorful fish, natural beauty, and maybe even the perfect underwater photo . Shirley Pomponi , a biologist at Florida Atlantic University's Harbor...
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...
This beautiful jewel squid ( Histioteuthis bonnellii ) can be found swimming above the Mid-Atlantic Ridge, at depths of 500-2,000 meters (1,640-6,562 feet). The “jewels” covering the body are...
I have been at the Smithsonian’s National Museum of Natural History since 1966, studying and reporting on all kinds of octopuses and squids . But I’ve always had a particular fascination with the...
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"...
A mass of white muscle the size of a softball surrounds the dark brown beak of a giant squid. Learn more about this animal's oversized anatomy in our Giant Squid section .
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...
In 1874 Reverend Moses Harvey of Newfoundland displayed the giant squid he bought on the side of his barn, much to the dismay of Mrs. Harvey. More about the giant squid can be found in our Giant...
Using a deep-diving ROV, the crew aboard Oceana’s research vessel Ranger were surprised to discover large colonies of deep-sea white coral in the Western Mediterranean Sea in July 2010. Most of the...
Stinging cells (nematocysts) line the tentacles of this moon jelly ( Aurelia aurita ). Upon contact with prey or a predator, a venom-laden harpoon shoots out to stun or kill. Read more about...
These large jellyfish ( Chrysaora fuscescens ) are most commonly found along the coasts of California and Oregon. (They're also popular in the displays of public aquaria.) Their bells can grow to a...
Seahorses are not just tropical creatures. They can be found in colder waters like those found off New Zealand, Argentina, Eastern Canada, and the UK. This long-snouted seahorse ( Hippocampus...
The Census of Marine Life - a ten-year effort by scientists from around the world to answer the age-old question, “What lives in the sea?” It was an international effort to asses the diversity,...
A pile of sea stars decomposing from starfish wasting syndrome on the coast of Vancouver in September 2013.
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