Land and oceans
White roofs could cool cities: study
Enzyme crystal helps crack HIV puzzle
Sugar sweetens decision making
Twilight zone secrets revealed
Astronomers spot asteroid collision
Algae master quantum mechanics
Protein 'ushers' key to beating malaria
Researchers spin artificial bee silk
New view of Pluto increases mystery
Cell's power packs came from within
Antarctic snow linked to WA dry
Termites inspire hydrophobic materials
Study shows why it's scary to lose money
Soil impact underestimated: climate study
Lack of oxygen forced fish's first breath
Harder Sudoku puzzles on the way?
Weed genes could help feed the world
Logging makes forests more flammable: study
Food crisis looms warn scientists
Tiny sensors track 'lost' objects
'Climategate' university orders review
'Plumbing' key to flowering success
New twist on solar cell design
Scientists set new temperature record
Lack of oxygen forced fish's first breath
A global drop in oxygen levels may have been the driver that led ancient fish to leave the water and evolve into the first air-breathing animals on land, suggests an Australian study.

The finding, published today in the Royal Society's journal Biology Letters, challenges the accepted wisdom about the environment from which tetrapods - the fish-like ancestors of land animals - first moved on to land.

Doctoral student Alice Clement, from the Australian National University's Research School of Earth Sciences, and Museum Victoria researcher Professor John Long, now based at the Natural History Museum of Los Angeles County, make the claim based on the fossilised remains of a fish that lived about 375 million years ago.

The new species of lungfish, known as Rhinodipterus, was found in the Gogo formation in northern Western Australia.
Modern link

Clement says a number of features found in modern lungfish that are important to its air-gulping behaviour were found in the fossil.

These included a long mouth cavity and cranial ribs that are attached to the base of the skull.

She says in modern lungfish the longer mouth cavity enables them to hold a bubble of air in their mouths, while the cranial ribs anchor the pectoral girdle during air gulping.

Yet while modern lungfish exist in freshwater environments, the Rhinodipterus lived in the ocean.

"This runs counter to the standard theory that fish evolved the ability to breath air once they moved to freshwater habitats [because marine water is more oxygenated than freshwater]," says Clement.

The researchers suggest low global oxygen levels during this period, known as the Devonian, may explain the evolution of air-gulping characteristics.
Gulping for air

Previous studies have shown oxygen levels fell as low as 12% of the total atmosphere. Today global oxygen levels are about 20%.

Long believes this plunge in global oxygen levels would have been a strong selection driver on some animals, such as tetrapods, to become air-breathers.

"In previous work, scientists thought fishes invading freshwater habitat would encounter pockets of low oxygen water - due to rotting plants - so this was thought to be the main driver for breathing air," he says.

"Now, because we have found a fossil lungfish in a marine environment that is an air-breather, it shows that entering a freshwater environment wasn't the main cause, it was global oxygen levels."

"This makes us believe that breathing air arose twice at this early time in vertebrate evolution: once in lungfishes, and once in the fish lineage leading to land animals, and ultimately to us."

Clement says their study is another step in explaining the evolutionary progression from ocean to land.

"It is a piece of the puzzle that contributes to the story of life [that is] tied so closely to our past, as well as to when fish moved out of the water to a terrestrial environment."

Horny mother beetles fight for dung
Light-speed computing one step closer
Small asteroids 'just lumps of gravel'
Gene study reveals diverse gut zoo
Dinosaur extinction caused by asteroid: study
Study finds methane bubbling from Arctic
New view reveals Mars' icy history
Some nano-sunscreens 'come at a cost'
Dust bunnies could harbour toxic load
Aphid genome reveals its 'Achilles heel'
Tailored diet may slow down DNA damage
Scientist probe ballistic chameleon tongue
Moa eggshells yield ancient DNA
Toothbrush tech helps buses go green
Gene protects some Tassie devils from tumour
Smaller fish cope better with acidic water
Lunar mirror mystery solved
Parents give fewer bad genes than thought
Women on pill may live longer
Antarctic winds affect key ocean layer
Researchers uncover thalidomide mystery
Boost for evidence of early ocean
Ocean geoengineering may prove lethal
People leave unique 'germ print'
Rogue star on collision course
Butterflies 'fly early as planet warms'
Glaucoma may start in the brain
Tools push back dates for humans on Flores
Stem cell capsules to target broken bones
Ecstasy damages complex memory: study
Earliest animals flexed their muscles
Insomnia may shrink the brain: study
Experts call for 'resilience thinking'
Tutu's DNA could point to medical cures
Humble algae key to whale evolution
Happiness linked to healthy heart
Fewer cyclones, but more intense: study
Cosmic candles result of colliding stars
Flightless mosquitoes may curb dengue
Childhood poverty may leave its mark
Cautious response to technology strategy
Nanowire RAM to make ever-ready computers
Are non-smokers smarter than smokers?
There's iron in them thar Martian hills
'Shell Crusher' shark swam ancient oceans
Nanotechnology may tap into your mind
Small dogs originated in the Middle East
Brain 'hears' sound of silence
Swimmers 'may not understand' tsunami risk
Altruism surfaces on slow-sinking ship
Chile quake tops Haiti, but less deadly
Weedkiller 'makes boy frogs lay eggs'
Visit Statistics