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The magnificent hidden world of microscopic plankton (pictures)

The three-year-long global Tara expedition has created the world's most complete catalogue of planktonic organisms, including thousands of new species.

Michelle Starr
Michelle Starr is CNET's science editor, and she hopes to get you as enthralled with the wonders of the universe as she is. When she's not daydreaming about flying through space, she's daydreaming about bats.
Michelle Starr
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1 of 10 Christian Sardet, "Plankton -- Wonders of the Drifting World", University of Chicago Press, 2015

Pulsating neon rainbow

In a special issue of Science magazine, a team of 160 scientists has published a series of papers detailing the findings of the Tara expedition. What did they discover? A massive world of microscopic creatures dwelling in seas all around the globe.

Comb jellies are the largest animals that use combs of hair-like cilia for swimming. This is one of the smaller species, which start at just a millimetre or so in length, but larger species range up to 1.5 metres.

When comb jellies swim, the rippling of their cilia causes light to refract, resulting in a rhythmic rainbow of neon colours. You can see a video of this effect in action here, and another here.

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2 of 10 M. Ormestad/KahiKai/Tara Oceans

The queen of the Xenomorphs?

This semitransparent prawnish-looking creature is an amphipod -- a type of crustacean with no carapace.

The female of the species feeds on jelly-like salps, leaving just a hollow gelatinous shell behind. It will then climb inside and use the empty barrel-shaped shell of the salp as a sort of mobile home, sailing the seas and snagging food, keeping her young safe inside.

Rumour has it that the tiny amphipod inspired the design of the Alien queen, Xenomorph Regina, from James Cameron's 1986 film, "Aliens." It's never been confirmed, but the resemblance is uncanny.

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3 of 10 Noan Le Bescot/CNRS/Tara Oceans

Miniature cyclops

Copepods -- a group of tiny crustaceans -- live all over the ocean. Some live on the seafloor, but this blue specimen was retrieved drifting in the ocean's current.

Most copepods are very small, measuring just a millimetre or two, and have a single compound eye in the centre of their transparent heads.

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4 of 10 M. Ormestad/KahiKai/Tara Oceans

Tiny and abundant

These little fish in the genus Cyclothone grow to just 6 centimetres long, and live at ocean depths greater than 300 metres.

This makes them difficult to catalogue, but the numbers found are extremely abundant. Although it is a small fish, ichthyologists theorise that the Cyclothone genus contains more individuals, and possibly more biomass, than any other fish genus in the world.

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5 of 10 Christian Sardet/CNRS/Tara Expéditions

Shell of glass

At 200 microns (0.2 millimetres), Lauderia annulata is one of the largest known kinds of single-celled algae. This one was found in the Indian Ocean.

The green and yellow speckles are chloroplasts, the algae's food-producing organelles; the entire organism is encased in a shell of silicon dioxide, a type of naturally occurring glass, similar to quartz or sand.

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6 of 10 Christian Sardet/CNRS/Sharif Mirshak/Parafilms/Tara Expéditions

Shimmering iridescence

This copepod, found in the Mediterranean Sea, is called Sapphirina -- the Sea Sapphire.

The male shimmers with an iridescent array of colour, created by microscopic layers of hexagonal crystal plates inside its skin cells. You can see a video of the phenomenon here.

To reproduce, the females parasitise salps. Poor salps, they can't seem to catch a break.

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7 of 10 C. Guiguand/Tara Oceans

Tiny squid

A tiny squid hatchling.

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8 of 10 Christian Sardet, "Plankton -- Wonders of the Drifting World", University of Chicago Press, 2015

Snacking jellyfish

The Lyriopemedusa is a very small jellyfish, measuring just 10 to 30 millimetres across. This individual has caught and devoured a juvenile fish in its tentacles. Photographer and Centre National de la Recherche Scientifique research director Christian Sardet captured the process.

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9 of 10 Christian Sardet/CNRS/Tara Expéditions

Underwater wings

On the right, with what looks like butterfly wings, is what is known as a sea butterfly (funnily enough).

Sea butterflies are a type of sea snail, that, unlike their mollusc cousins, can swim, using a foot that forms a pair of wing-like flaps. It lives close to the sea's surface and doesn't usually get bigger than 10 millimetres long.

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10 of 10 Eric Roettinger/KahiKai/Tara Oceans

Ancient worm of the sea

Marine ragworm Platynereis dumerilii isn't your ordinary ragworm. It's considered a living fossil, having survived for millions of years in the same environment, still with many of the same features as its ancestors.

This makes it a very good study case for evolution -- in particular its eyespots. Eyespots are the most primitive form of eyes, able only to detect the presence of light, which allows the worm to navigate. Everything else, it performs using touch. These eyespots, scientists theorise, are the nearest existing formation to the earliest evolution of eyes.

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