Saturday, December 25, 2010

Penguin Evolution Revisited

Click photo to enlarge
University of Otago geologist Assoc Prof Ewan Fordyce examines a fossilised penguin wing bone that shows signs of a grooves heat-retention mechanism. Photo by Jane Dawber.
University of Otago geologist Assoc Prof Ewan Fordyce examines a fossilised penguin wing bone that shows signs of a grooves heat-retention mechanism. Photo by Jane Dawber.
Most people think of penguins as cold-water or polar birds, but latest research linked to the University of Otago sheds new light on that traditional view. A research paper published last week in British-based journal Biology Letters also offers new insights into the evolutionary development of penguins.
The paper's first author is Dr Daniel Thomas, a New Zealander who is a postdoctoral fellow at the University of Cape Town, South Africa.
His recent Otago doctorate was supervised by Associate Prof Ewan Fordyce, who heads the Otago University geology department.
Prof Fordyce, who also contributed to the paper, said it had long been believed that penguins thrived by adapting to increasingly cold conditions, including in the now largely ice-covered Antarctic.
This region, which had earlier been semi-tropical, became glaciated about 34 million years ago.
However, the paper points out that, much earlier, about 49 million years ago, penguins lived in much warmer conditions, when some ocean surface temperatures were about 25degC.
And it was at that stage that penguins evolved a key heat-retention mechanism that effectively pre-adapted them to thrive in later, much colder, conditions, including in the Antarctic.
It seemed ''counterintuitive'' for such mechanisms to evolve at a time of global warmth, but researchers suspected that the evolutionary change occurred then ''to allow penguins to forage for food in cool depths, far below the warm surface waters'', Prof Fordyce said.
Faced with a ''constant threat from hypothermia'' in deep, cold waters, penguins had developed a ''counter-current heat exchanger'', which managed the flow of blood along the wing and significantly improved heat retention and energy efficiency.
Wings were used to help propel the birds through the water.
Prof Fordyce said grooves in fossilised wing bones showed evidence of this mechanism.
By the mechanism, warmer blood that was being moved out to the wings was also used to heat the cooler blood coming back from the wings before it re-entered the penguin body core.
Dr Thomas was a ''very, very good researcher'' and the study highlighted the ''power of fossils'' to show how animals had evolved, Prof Fordyce said.


Penguins Weren't Always Adapted to the Cold

Palaeeudyptes, one of the "giant" penguins lived during the Oligocene, about 28 million years ago. Bones in this bird and its relatives show clear evidence of a heat-conserving structure known as a humeral arterial plexus. Credit: the Geology Museum, University of Otago, Dunedin, New Zealand.

How Penguins Got Their Cold-Weather Coats

By Charles Q. Choi, LiveScience Contributor
posted: 21 December 2010
Those tuxedo-wearing birds that inhabit Earth's coldest continent may have evolved a means of retaining heat when they were still living in warm climates, scientists now suggest.
A key adaptation that helped modern penguins to invade the cold waters of Antarctica within the last 16 million years is the so-called humeral arterial plexus, a network of blood vessels that limits heat loss through the wings.

The plexus routes blood coming into the body from the wings past the blood traveling from the body to the wings. As such, the cooler blood from the wings, which get cold in the water, is heated up by warmer blood from the body, thus conserving heat.

To find out more about how this anatomical structure evolved, scientists investigated seven live penguin species and 19 fossil ones. In live specimens, they found the plexus leaves behind grooves in the upper arm bone called the humerus. As such, they could see when this structure began appearing in extinct penguin species from the fossil record.

Surprisingly, they found the plexus arose at least 49 million years ago, when the planet was going through a warm "greenhouse Earth" phase due to vast amounts of global warming gases that got pumped into the atmosphere, perhaps by volcanism. 

"I began this work thinking we would relate heat retention in penguins to the global cooling that took place at the Eocene-Oligocene boundary [about 34 million years ago], whereas in fact, penguins were cold-water-tolerant millions of years earlier," researcher Daniel Thomas, a paleontologist at the University of Cape Town in South Africa, told LiveScience.

The earliest known penguins to feature the plexus lived on the lost continent of Gondwana, on what is now Seymour Island in Antarctica. Back then, the waters there were 59 degrees Fahrenheit (15 degrees Celsius), compared with the water's current average temperature of 34 degrees F (1 degree C). (Scientists can deduce ancient temperatures by looking at the chemistry of fossils — for instance, magnesium levels in the shells of certain organisms rise as temperatures go up.)

The researchers suspect the plexus first evolved to help penguins save energy during long foraging trips in the cold water, as the structure evolved in concert with dramatic skeletal changes that promoted buoyancy and reduced drag, thus improving deep-diving and long-distance swimming. As global climate cooled, the plexus then found a new use, proving key to the penguins' invasion of Antarctic ice sheets. 

"Penguins have occupied much of the Southern Hemisphere in the last 40 million years because of their tolerance for cold water," Thomas said.

Thomas and his colleagues Dan Ksepka and Ewan Fordyce detailed their findings online Dec. 22 in the journal Biology Letters.

The pink underside of the yellow-eyed penguin's wings shows how its heat-regulating humeral arterial plexus looks from the outside. Credit: Daniel Thomas.


Wednesday, December 15, 2010

Busy Adeliés

Penguin Update from Dr. Dee Boersma

Hello Penguin Lovers and Supporters --
Here's a penguin update. Chicks have hatched!! We know that the Punta Tombo colony covers 400 hectares and the update tells you how many active nests we estimate from survey data in 1987 and 2006. Read to see what you helped us accomplish. Thanks for your interest in the penguins of patagonia and Happy Holidays.

P. Dee Boersma, Ph.D
Wadsworth Endowed Chair in Conservation Science
Department of Biology, Box 351800
University of Washington
Seattle, WA 98195-1800
Phone: 206-616-2185
Fax: 206-221-7839

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