Pictures: Hard-to-See Sea Creatures Revealed

Hard-to-See Stunner
Photograph courtesy Cheryl Clarke-Hopcroft/UAF/CMarZ
This leggy creature may look like an octopus, but it's actually an immature, or larval, tube anemone (picture of an adult tube anemone).
(Watch video of the tiny sea creatures.)
Despite being so young and only about 0.4 inch (1 centimeter) wide, the anemone larva has already begun fishing with the tentacles it will use as an adult. This specimen's dark stomach suggests it's already a successful hunter, experts say.
The anemone larva was recently inventoried during the Census of Marine Life, a series of ocean projects aimed at documenting the myriad life-forms that live in Earth's oceans. On Sunday, the census announced results of a far-ranging study of hard-to-see sea species—microscopic animals, plankton, larvae, and burrowers.
"The ocean represents about 90 percent of the habitat on the planet, in terms of volume, whereas organisms on land only live within about a hundred meters [328 feet]" of sea level, said Ron O'Dor, a senior scientist with the Census of Marine Life.
"So there is a huge volume out there capable of supporting different kinds of life."
—Ker Than
Published April 16, 2010
Fresh Fish
Photograph courtesy Cheryl Clarke-Hopcroft/UAF/CMarz
This bulbous-headed creature is an anglerfish that's just hatched from its egg. The larvae of many deep-sea fish are still virtually unknown to science.
"In many cases, we only know the adults," said Ron O'dor of the Census of Marine Life. "And the description of the species is based on the adult."
Like many marine life-forms, anglerfish spend their youths as plankton—very small or even microscopic creatures that drift with the ocean currents. Scientists think many marine creatures spend parts of their life cycles this way because it allows the animals to take advantage of other plankton as food and to be carried by ocean currents to far-flung regions before they have to grow up and settle down.
"Even the giant squid hatches as something less than a millimeter [0.04 inch] long," O'dor said.
Published April 16, 2010
Base of the Pyramid
Photograph courtesy D. J. Patterson, L Amaral-Zettler, M. Peglar and T. Nerad
Ten single-celled ocean amoebas known as Chlamydophrys band together.
Identifying hard-to-see sea species and understanding the environmental role of each is critical for understanding the Earth's food web, carbon cycle, and other planetary processes, said Ron O'dor of the Census of Marine Life.
"In ocean food webs, microbes are at the bottom, and everybody eats them," he said. "Typically, crustaceans eat the microbes, and they in turn get eaten by fish, which get eaten by bigger fish, and we catch them.
"It's a giant pyramid, and at the bottom of it are the microbes."
Published April 16, 2010
Finding Its Sea Legs
Photograph courtesy Cheryl Clarke-Hopcroft/UAF/CMarZ
Compared to the hard-to-see creature in this gallery's first frame, this transparent creature—its legs still stubs—is an even younger form of a tube anemone.
Scientists estimate that the microscopic organisms in the oceans' water column collectively weigh the equivalent of 240 billion African elephants.
Despite their abundance, these creatures have remained largely unnoticed because of their small size. The new Census of Marine Life study, to be formally released this fall, aims to change all that.
Published April 16, 2010
Mighty Microbe
Photograph courtesy Bob Andersen and D. J. Patterson
Beware the blob. Karenia brevis (such as the cluster pictured) is a toxic plantlike species known as a dinoflagellate. The microbes form "red tide" blooms in Texas and Florida, which can kill fish, turn shellfish toxic, and irritate human skin and respiratory systems.
To identify new species that are invisible to the naked eye, scientists rely on DNA-sequencing technologies.
After drawing ocean samples from more than 1,200 sites worldwide, Census of Marine Life scientists have amassed a database that includes 18 million DNA sequences of microbial life, spanning more than a hundred major phyla—groupings based on body plan.
Published April 16, 2010
Pint-Size Pricklepuss
Photograph courtesy Cheryl Clarke-Hopcroft/UAF/CMarz
Only a few millimeters across, this prickly creature is a larval spider crab. The numerous spines on its body deter predators from eating it, but they also help to create drag in the water to keep the crab from sinking.
Only about 20,000 marine microbes have been identified, according to Census of Marine Life scientist John Baross of the University of Washington.
But the new Census of Marine Life data suggest the number of sea microbes may be closer to a billion—and 20 million may be only bacteria.
"This is a huge frontier for the next decade," Baross said in a statement.
Published April 16, 2010
Rising Stars
Photograph courtesy Russ Hopcroft/UAF/CMarZ
Looking like extraterrestrials with bizarre body plans, these creatures are the larvae of sea stars, or starfish. They'll become more symmetrical and starlike as they grow older.
"The series of cruises that these pictures are from are focused on things you can't see normally, or that are tiny and people don't notice them," the Census of Marine Life's O'dor said. "But they're a very important component of the ocean ecosystem."
Published April 16, 2010
Ancient Algae
Photograph courtesy D. J. Patterson, L. Amaral-Zettler and V. Edgcomb
It looks like a worm, but this filamentous structure studied by the Census of Marine Life is actually several blue-green algae cells stuck together. Joined like this, the microbes are often mobile and can be found gliding through the ocean.
Algae are probably the oldest recognizable organisms on Earth: Scientists have found algae fossils that are more than three billion years old.
Published April 16, 2010
Twinkle, Twinkle ...
Photograph courtesy Linda Amaral Zettler
Looking more like a supernova than an ocean microbe, this acantharian represents one of four types of large amoebas that occur in open marine waters.
Their fragile skeletons are made of single crystals of strontium sulfate that quickly dissolve after the cells die, according to Census of Marine Life scientists.
Published April 16, 2010
Buried Treasure
Photograph courtesy Gunnar Gad and Marco Büntzow
This radioactive-looking creature is a new species of loriciferan, burrowing microbes that live in the seafloor. The species was discovered last year at a depth of 2.6 miles (4 kilometers), in a region of ocean just south of Africa's Côte d'Ivoire (Ivory Coast).
Loriciferans are among the smallest known multicellular marine animals, and some of them are known to be able to survive without oxygen. This specimen is only about as wide as three human hairs, according to the new Census of Marine Life report.
Published April 16, 2010
Tiny Bubbles
Photograph courtesy Colomban de Vargas, EPPO/SBRoscoff
These pink bubbles are live planktonic foraminifera taken from the Sargasso Sea in the North Atlantic Ocean.
Each set of bubbles is a single-celled creature that has built itself a protective, multichambered house called a test, according to Census of Marine Life experts.
Published April 16, 2010
Portrait of the Worm as a Young Helmet
Photograph courtesy Russ Hopcroft/UAF/CoML
This bell-shaped larva will grow up to become a marine acorn worm. Like other forms of part-time plankton, this creature will drift around in the ocean currents, feeding and growing, before settling down, according to Census of Marine Life scientists.
(See pictures of unearthly worms found off Hawaii.)
Published April 16, 2010