Scientists have announced that they are testing a plan to train fish to catch themselves by swimming into a net when they hear a tone that signals feeding time.

If it works, the system could eventually allow black sea bass to be released into the open ocean, where they would grow to market size, then swim into an underwater cage when they hear the signal.

The key question for fish farmers: How many fish will actually return, and how many will be lost to predators or simply swim away?

Saliva tests make diagnosis advance

U.S. researchers have identified all 1,116 unique proteins found in human saliva glands, a discovery that they say could usher in a wave of convenient spit-based diagnostic tests to replace the drawing of blood.

As many as 20% of the proteins that are found in saliva are also found in blood, they said. The researchers hope saliva-based tests can be used to diagnose cancer, heart disease, diabetes and a number of other conditions, they report in the Journal of Proteome Research.

Like a genome, which lists all of the genes in an organism, a proteome is a complete map of proteins. While genes provide the instruction manual, proteins carry out the instructions by regulating cellular processes.

Explorer gives up North Pole effort

British explorer Hannah McKeand has called off her attempt to become the first woman to reach the North Pole alone and unaided after falling through ice and injuring herself.

Setting out from Canada's Ward Hunt Island on March 8, she'd hoped to ski, walk and swim the 478 miles to the pole in 60 days.

McKeand, 34, hurt her leg, back and shoulder when she fell into an 8-foot-deep hole in the polar ice the night of March 20. She was 45 miles north of her starting point. The pole can get as cold as minus 76 degrees.

Her expedition manager announced Sunday that McKeand had called off her effort.

Folate may ease damage to hearts

Studies in rats show that high doses of folate, already used to prevent anemia in pregnant women and to prevent birth defects, can blunt the effects of heart attacks, researchers from Johns Hopkins University say.

Giving the supplement for days before a heart attack or infusing it into the bloodstream during an attack reduced damage to the heart by 90%, they found in a study that will be published next month in the journal Circulation.

The researchers cautioned that people should not self-medicate until a clinical trial can be performed, but they held out hope that the supplement could be used prophylactically in people at high risk for heart attacks and to treat victims.

Study finds ants longtime farmers

Ants took up farming some 50 million years ago, according to researchers who traced the ancestry of farmer ants.

An analysis of the DNA of farmer ants traced them back to an original ancestor -- a sort of Adam ant, at least for the types that raise their own food, according to a paper published in the online edition of Proceedings of the National Academy of Sciences.

In the last 25 million years, ants have developed different types of farming, including the well-known leaf-cutter ants. Leaf-cutter ants don't eat the leaves they collect. Instead, they grow fungus on the leaves and eat the fungus.

Only four types of animals are known to farm for food -- ants, termites, bark beetles and, of course, humans. All four cultivate fungi.

Fossil shows crocs outdid dinosaurs

A fossil of a new marine crocodile species found in Brazil shows the reptiles survived the extinction of dinosaurs 65 million years ago, researchers say.

Brazilian paleontologists said the discovery of the fossil of the 10-foot-long Guarinisuchus munizi, dubbed "Sea Warrior," also engendered a new theory on the migration of prehistoric crocodiles from Africa to South and then North America.

The 62-million-year-old fossil, described in the Proceedings of Royal Society B research journal, is part of the Dyrosauridae group, which replaced mosasaurs, or serpentine marine lizards, as the dominant marine predators in the Paleocene epoch.