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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Seaside Lichens

Horizontal bands of color represent different species of lichen that have...

DIVE DEEPER

Diversity of Deep-Sea Corals

Sample the surprising diversity of deep-sea corals. See some of the ways they differ in color, shape, and size. Explore more...
A photo of a squid using bioluminescence to hide in the deep sea.

Bioluminescence

You may have seen the sparkle of fireflies on a summer’s night. The fireflies produce light through a chemical reaction in their glowing abdomens, a process known as bioluminescence. But did you know that...

Blackwater Drifting

Some of the most otherworldly animals—like those straight from a science fiction story—can be seen in the open ocean at night. By drifting in the blackwater in a scuba suit just under the surface,...

Masters of Disguise

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 Marine...
A blue-ringed octopus

How Octopuses and Squids Change Color

Video of Where's The Octopus? by Fox Meyer Squids, octopuses, and cuttlefishes are among the few animals in the world that can change the color of their skin in the blink of an eye...
Hawaiian Monk Seal

Endangered Ocean Animals

The Endangered Species Act (ESA) was signed into law on December 28, 1973 by President Nixon. Over 2,000 species are currently on the ESA, and they are separated into "Threatened" and "Endangered" species. Endangered...
A decomposing sea star loses its grip on a rock.

Sickly Starfish: A Q&A with Dr. Chris Mah

A morning sun star ( Solaster dawsoni ) loses its grip on a rock surface as its body slowly decomposes from starfish wasting syndrome off the coast of Vancouver in September 2013. Credit: Jonathan...
A nudibranch showing a closeup of their fleshy, tentacle-like growths, called cerata.

How Sea Slugs Steal the Defenses of Their Prey

Many tentacle-like outgrowths, called cerata (singular: ceras), project off the back of this aeolid nudibranch. After the nudibranch eats the tentacles of a jellyfish, anemone, coral, or other stinging animal, the stolen stinging cells...
A reddish-orange nudibranch.

A Collage of Nudibranch Colors

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,...
Small foram shells in seafloor sediment.

Little Critters that tell a BIG Story: Benthic Foraminifera and the Gulf Oil Spill

You are not alone if you don’t know what forams (short for foraminifera) are, so let’s start with the basics. Simply put, forams are single-celled organisms related to the familiar amoeba that produce a...
Small red hyperiid.

The Hyper Eyes of Hyperiids: How Some Shrimp-Like Creatures See Light in the Deep Sea

Hyperiid amphipods are small crustaceans related to sand fleas and distantly related to shrimp. They range in size from very tiny to more than 7 inches long, and are found at all depths of...

Oil Invades Coral Communities of the Deep

On the deep seafloor of the Gulf of Mexico, ecosystems made up of fish, corals, sea stars, anemones and other invertebrates flourish. Since the sun’s rays don’t reach the deep sea, coral communities rely...
An albatross soars over the ocean.

Is It Love? Why Some Ocean Animals (Sort Of) Mate For Life

We often hear stories of animal love— tales of rare monogamy in the animal kingdom where life-long love is implied. But there is a distinction between romantic love and an efficient mating system. Here’s...

The Discovery of Two Extreme Sea Stars

Two new species of sea stars were discovered in the deep sea: Paulasterias tyleri (on the left) in a North Pacific hydrothermal vent community, and Paulasterias mcclaini (on the right) in the deep sea...

Art Forms in Nature: Marine Species From Ernst Haeckel

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 providing free and open access to this...
Colorful scaleworm on a seastar

Pops of Polychaete Color

Beautiful worms? These stunning images from Alexander Semenov prove that this isn't an oxymoron. Polychaete worms are found throughout the oceans and (as the images below prove) they are a diverse and colorful group...

Why I Love Polychaetes

Credit: © 2008 K.J. Osborn Polychaete worms are not your average cringe-inducing, writhing worms. (Okay, maybe some are.) They are fascinating, varied, and a critical part of our ocean. The visual variety among the...

Spirals in Time: A Walk at the Seashore

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...

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