Tuesday, March 25, 2014

Missing hormone in birds

Leptin found in mallard duck, peregrine falcon and zebra finch

Date:

March 24, 2014

Source:

University of Akron

Summary:

How does the Arctic tern (a sea bird) fly more than 80,000 miles in its roundtrip North Pole-to-South Pole migration? How does the Emperor penguin incubate eggs for months during the Antarctic winter without eating? These physiological gymnastics would usually be influenced by leptin, the hormone that regulates body fat storage, metabolism and appetite. However, leptin has gone missing in birds -- until now.

Male mallard duck. University of Akron researchers discovered leptin in the mallard duck, peregrine falcon and zebra finch, marking the first time the hormone has been found in birds.

Credit: Image courtesy of University of Akron

How does the Arctic tern (a sea bird) fly more than 80,000 miles in its roundtrip North Pole-to-South Pole migration? How does the Emperor penguin incubate eggs for months during the Antarctic winter without eating? How does the Rufous hummingbird, which weighs less than a nickel, migrate from British Columbia to Mexico? These physiological gymnastics would usually be influenced by leptin, the hormone that regulates body fat storage, metabolism and appetite. However, leptin has gone missing in birds -- until now.

UA Professor of Biology R. Joel Duff made the initial discovery by comparing ancient fish and reptile leptins to predict the bird sequence. Duff, along with undergraduate students Cameron Schmidt and Donald Gasper, identified the sequence in multiple bird genomes and found that the genomic region where leptin was found is similar to that of other vertebrates. Jeremy Prokop, a former UA Integrated Bioscience doctoral student who initiated the project, then constructed computer models of the bird leptin's three-dimensional structure and performed bench experiments to show that the bird leptin can bind to a bird leptin receptor. Richard Londraville, research team member and UA professor of biology, says that the search for leptin in birds has been a bit of a race among scientists.

Crucial discovery "It has been a pretty big deal because people wanted to study leptin in birds for the poultry industry, for instance, to develop faster growing and tastier chicken," Londraville says, noting that, interestingly, leptin has yet to be discovered in chickens, perhaps because their gene structure varies from that of other birds.

Robert Dores, editor-in-chief of the journal General and Comparative Endocrinology, says the discovery represents a significant turning point in leptin study. "This study now sets the stage for future studies on the evolution of leptin function ... and reinforces that studies on hormone sequences should be complemented by hormone receptor modeling studies," says Dores, a University of Denver professor of biological sciences. "The world of comparative endocrinology has entered the 21^st century."

Story Source:
The above story is based on materials provided by University of Akron. Note: Materials may be edited for content and length.

Journal Reference:

Jeremy W. Prokop, Cameron Schmidt, Donald Gasper, Robert J. Duff, Amy Milsted, Takeshi Ohkubo, Hope C. Ball, Matthew D. Shawkey, Herman L. Mays Jr, Larry A. Cogburn, Richard L. Londraville. Discovery of the Elusive Leptin in Birds: Identification of Several ‘Missing Links’ in the Evolution of Leptin and Its Receptor. PLoS ONE, March 2014; DOI: 10.1371/journal.pone.0092751

University of Akron. "Missing hormone in birds: Leptin found in mallard duck, peregrine falcon and zebra finch." ScienceDaily. ScienceDaily, 24 March 2014. <www.sciencedaily.com/releases/2014/03/140324184227.htm>.

Saturday, March 22, 2014

Global warming sees predator gulls thrive and pose threat to penguins

Late summers spark rise in predator gull numbers in Chile bird paradise

PUBLISHED : Friday, 21 March, 2014

Global warming could threaten the long-term survival of penguins. Photo: Xinhua

Magdalena Island, near Chile's southern tip, is a natural paradise for tens of thousands of penguins that come every year to breeYet global warming could threaten the long-term survival of the species, say experts at the island nature reserve in the Strait of Magellan, about 50 kilometres from the city of Punta Arenas.

The island is home to 22 bird species - 11 that nest all the year round and 11 seasonal visitors - including Magellanic penguins.

About 23,000 tourists a year make the pilgrimage to Los Pinguinos Natural Monument, a protected area comprising tiny Marta Island and windswept Magdalena Island.

The penguins' main predators were aggressive seabirds called skuas and Dominican gulls, which feed on penguin eggs and young, says Roberto Fernandez, a ranger at the site.

Right now, the population of these predators was growing. "We are seeing summer starting late, then lasting through into March; climate change is bringing about a rise in gull numbers," says monument administrator Neftali Aroca.

"You would have to undertake a long-term study in order to link this increase with a reduction in the penguin population, but the forecast is that in the future, the penguins could be at risk."

The worrying prognosis seems to confirm fears raised in January in a study published in the scientific journal PLOS ONE, which indicated that extreme weather conditions, such as unseasonable warmth and heavy rainfall, may have killed off a considerable number of young Magellanic penguins.

The study - conducted over 27 years in Argentina's Punta Tombo peninsula, the largest breeding ground for the species - showed that, on average, 65 per cent of the colony's young died annually, 40 per cent from hunger and 7 per cent because of the effects of climate change.

Each year, the penguins flee the cold to spend winter in the warmer waters off Brazil. As soon as they are big enough to swim, they head off on a 4,000-kilometre journey from Magdalena Island to Brazil.

They spend the Southern Hemisphere winter on the coast of Brazil's southern Santa Catarina state - though they sometimes make it as far up as Rio de Janeiro's beaches.

From mid-August, they begin to head back, via Uruguay and Argentina to the Strait of Magellan, the natural passage between the Atlantic and Pacific oceans, and Magdalena Island.

"Magellanic penguins come to the island to complete their reproductive cycle," says Valeria Sanchez, who has spent five years as a tour guide here."

They start arriving in September, as summer approaches, to enjoy the longer days necessary to incubate their eggs and look after their young."
Magellanic penguins, which can live up to 25 years, are monogamous and share their lives with only one partner.

First to arrive on Magdalena Island are the males, who must seek out the burrowed nests dug the previous season and make any necessary changes with whatever material they can find, including stones and feathers, before attracting their mate.

About a fortnight later, the females arrive, and their keen partners sound a trumpet-like call to guide them to the nest.

After fertilisation, the female penguin lays one or two eggs; for the first 12days, she will incubate them and not leave them - even to eat.

Following their long fast, the mothers give way to the males so they can feed. The couples switch at roughly fortnightly intervals until the end of the 40-to-45-day incubation period ahead of hatching in around November.

"Between February and March, they start to leave the island, but this year they began leaving two or three weeks earlier," Sanchez says. This article appeared in the South China Morning Post print edition as Global warming threatens penguins

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Saturday, March 15, 2014

Can penguins cope with climate change? Scientists find different types of ice elicit different responses

mongabay.com
March 13, 2014

Pygoscelis adeliae). In an article recently published in PLOS ONE, a team of researchers led by Amélie Lescroël from the Centre d'Ecologie Fonctionnelle et Evolutive (CNRS) in France, found that changes in sea-ice content and newly formed icebergs significantly impacted Adélie penguin communities in the Ross Sea.

Climate change is leading to major shifts in sea ice. One of the largest glaciers in Antarctica has begun to melt at a rate some scientists describe as irreversible. Pine Island Glacier contributes a fourth of the discharge of the West Antarctic Ice Sheet. It is estimated that if this entire ice sheet were to melt, sea levels would rise by ten feet. Other areas of the Antarctic are experiencing cooling events, resulting in greater ice coverage known as "fast ice." However, scientists believe that melting will supplant fast ice in the near future.

An Adélie Penguin (Pygoscelis adeliae). Photo courtesy of Reinhard Jahn under a Creative Commons Attribution-Share Alike 2.0 Germany license.

"While net sea ice cover (i.e., the area of ocean covered by ice) has increased over the past few decades [in Antarctica] owing to wind changes brought largely by mid-latitude warming and the Antarctic Ozone Hole, modeled predictions point to a decrease by 5-15 percent, depending on sector, by 2025-2052," the study states. "Concomitantly, increased ice shelf instability will lead to more frequent iceberg calving, including very large icebergs (hundreds of square kilometers)."

Sea ice cover variability directly affects Adélie habitat, and the species' ability to adjust to this variability will determine their future.

Adélie penguins depend on sea-ice for foraging, resting, molting, breeding and migrating. They are one of only two penguin species that depend on sea ice and not icebergs, the other being the Emperor penguin (Aptenodytes forsteri).

"This 'dependence' is actually a manifestation of them being the only penguin species that are able to cope with sea ice," Lescroël told mongabay.com.

To a certain extent, Adélie penguins are adapted to cope with changes in their habitat. For instance, they're able to easily gain and lose fat depending on ice conditions, and dive for longer periods of time compared to other penguin species.

"They dive mostly between 10 and 50 meters deep to catch their prey but can dive up to 180 meters, which is a world record," said Lescroël.

The southernmost extent of Adélie habitat is the Ross Sea, where 38 percent of the world's population resides. Lescroël and her colleagues evaluated data that had been collected over thirteen years at Cape Crozier on Ross Island, a volcanic island located near the Antarctic mainland.

The researchers conducted their study in a fenced-in nesting area installed in 1996, allowing penguins access through only one entrance outfitted with a scale. They collected each penguin's trip duration as well as changes in weight within breeding seasons and over multiple years. Using these data, the researchers were able to record how long it took the penguins to forage and how much food they brought back to their chicks.

"When they are nesting, parents take turns on the eggs or chicks," Lescroël said. "One of the parents stays at the nest while the other goes [to] sea to catch food. On Ross Island, Adélie penguins feed on crystal krill and silverfish. They swallow the prey as they catch it, underwater. When they come back to the nest, they regurgitate the food to their chicks."

Since Adélie penguins depend on sea-ice, one might expect the increased presence of "fast ice" in some areas would equate to habitat expansion. However, the study's findings indicate this is not necessarily so. When there was less sea-ice, the penguins were able to fish for longer periods of time and bring more food back to their chicks.

"This is mainly because when there is lots of concentrated sea ice, penguins have to walk over the sea ice (rather than swim) to reach the open water where they could dive," Lescroël said. "This is more costly in time and energy. But this is when environmental conditions are "normal."

In the middle of the study, when four giant icebergs broke off as a result of increased melting the research team labeled this as an extreme environmental event. The icebergs were present in Cape Crozier's landscape for 5 years, and the unique event allowed the team to observe how Adélie penguins responded to icebergs.

"The presence of these icebergs dramatically changed the physical environment of the penguins in many ways: less open water was available for diving; penguins were disoriented due to the movements of these huge blocks of ice just in front of the colony; there was less ocean productivity in the first year; and there were changes in the drift pattern of pack ice," Lescroël said, adding that "the changes were so extreme that sea ice concentration did not matter anymore. The foraging efficiency of Adélie penguins was constrained to lower levels during these five years, no matter what the sea ice concentration was."

While the icebergs were present, fewer chicks were reared than usual although the number of adults was not affected. However, soon after the icebergs left the area, breeding levels returned to normal.

"Our work shows that if the frequency of such extreme events increases, then it will become very hard to predict how penguin populations will buffer future sea ice changes," Lescroël said.

Map of the study area provided in the PLoS ONE article. The colony location is indicated by the star, the foraging area of Adelie penguins (in red) and where the giant icebergs were located. Satellite images are from http://lance-modis.osdis.nasa.gov. A: Illustrates a typical iceberg year (Dec. 21, 2004). B: Illustrates a typical non-iceberg year (Dec. 21, 2008).

Citations: Lescroël A, Ballard G, Grémillet D, Authier M, Ainley DG (2014) Antarctic Climate Change: Extreme Events Disrupt Plastic Phenotypic Response in Adélie Penguins. PLoS ONE 9(1): e85291. doi:10.1371/journal.pone.0085291

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