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Science Notes: Leatherback turtles keep swimming south; ancient arthropod feasted on plankton

Leatherback turtles keep swimming south

Leatherback turtles can travel thousands of miles through the ocean each year. Yet when females are ready to nest, they somehow manage to return to the same beach again and again.

Some studies have indicated that their palm-size hatchlings orient themselves to Earth’s magnetic field. A study published in the Proceedings of the Royal Society B finds that the turtles may use the field to navigate in adulthood, too.

Scientists at the National Oceanic and Atmospheric Administration tracked 15 leatherback turtles with GPS tags from August 2007 to September 2009. The turtles swam from their feeding grounds off the coast of Massachusetts to the western Atlantic subtropical gyre, a great swirl of ocean currents circulating from the equator almost to Iceland and from the East Coast to Europe and Africa. The researchers found that despite being in the currents, the turtles were able to keep moving south.

“They were able to maintain their orientation during day and night,” said Kara Dodge, an NOAA marine biologist in Woods Hole, Mass., and an author of the new paper. “This suggests they are using the Earth’s magnetic field.”

Ancient arthropod feasted on plankton

A huge arthropod that lived 480 million years ago used spines on its head to filter seawater and to trap tiny particles of food. The lobsterlike animal, 6 feet long, is one of the earliest giant filter-feeders ever discovered, scientists reported in Nature.

“It implies there was a rich source of plankton at the time, upon which these things may have fed,” said Derek Briggs, a paleontologist at Yale University and one of the study’s authors.

Briggs and his colleagues discovered the fossil remains of the new species, named Aegirocassis benmoulae, in Morocco. It belongs to an extinct family of marine animals called anomalocaridids, which first appeared during the Cambrian period 520 million years ago.

Aegirocassis had double flaps along the side of its body, rather than the single flaps seen in previous anomalocaridid fossils. The bottom flaps may have helped Aegirocassis swim, while the top set of flaps may have been used for stabilization.

The fossil remains are three-dimensional and very well preserved. Almost all previous anomalocaridid fossils were flat.

“We think it is because these things were buried quite rapidly by a storm or other event on the sea floor,” Briggs said.

– New York Times