What's going on down there? 2,000 ocean scientists do the biggest, wettest census ever

Science News,  Feb 17, 2007  by Susan Milius

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LITTLE GUYS Gauging the diversity of smaller creatures isn't necessarily straightforward under water. The tropics have long been hailed as rich in species, yet sea spiders may be most diverse in, of all places, Antarctica. "Some of the most amazing species live there, like those with one or two extra body segments,' says Claudia Arango of the Queensland Museum in South Bank, Australia.

The sea spiders, or pycnogonids, arise from an ancient lineage of arthropods and look like their sister group of terrestrial spiders. The sea spiders have some social skills, such as male parenting, Mango notes. She says that she's looking forward to using samples collected from census expeditions to clarify sea spiders' evolutionary history.

The census also stumbled upon a new species of the so-called Jurassic shrimp. To the trained eye, like that of the creature's discoverer Bertrand Richer de Forges, that shrimp looks impossibly ancient, as if a small, pinkish dinosaur had come to life.

Crustaceans such as this may have given rise to modern decapod crustaceans, including lobsters and crabs as well as shrimp. Scientists had assumed that the lineage went extinct some 50 million years ago. But in 1908, a U.S. research vessel in the Philippines caught a single shrimp that belonged to this group. This living fossil sat generally unnoticed in a museum of the Smithsonian Institution for 67 years before two French scientists recognized what it was. Biologists have since collected only about two dozen more specimens.

In October 2005, Richer de Forges of the Institute of Research for Development in New Caledonia led a cruise to the Coral Sea as part of the Census of Marine Life. A collecting net slowly trawling a rocky, uncharted surface at a depth of 400 to 500 m brought up another shrimp with the ancient characteristics. "We immediately recognized the very special shape,' Richer de Forges says.

He described it as a new species in the March 31, 2006 Zoosystema. Since then, another systematist has given it a genus of its own, and it's now called Laurentaeglyphea neocaledonica.

Even smaller animals are providing surprises for the census, says Russell Hopcroft of the University of Alaska, Fairbanks. He studies zooplankton, animals that are weak swimmers and so are swept along with ocean currents. In this category, there's "incredible diversity," Hopcroft says.

The group includes members from at least 15 or so animal phyla, the big categories just below kingdoms. "It's much easier to find new species than it is to find time to work up the descriptions," says Hopcroft.

For example, one cruise in the Arctic doubled the known diversity of comb jellies there, from 5 species to 10. Comb jellies have the same diaphanous look as jellyfish but aren't closely related to them. Ranging in size from a few millimeters to perhaps a third of a meter for rare oceanic species, they move by beating rows of tiny paddles and prey on other jellylike animals.