Thursday, August 27, 2015

New fossil skulls reveal insights about penguin brain evolution

August 27, 2015 by Annegret Kalus 

This Eocene Antarctic fossil penguin skull was discovered at La Meseta Formation at Seymour Island. Credit: Journal of Vertebrate Paleontology
When they're not being the stars of various animated movies, penguins are playing an important role in evolutionary studies. Penguins are unique among modern birds in that they 'fly' through the water. Although flightless in air, penguins have a number of adaptations which allow them glide effortlessly through the water. And some of these adaptations are in an unlikely part of their anatomy - their brains. Recent finds of fossil penguins from 35 million year old sediments in Antarctica have begun to shed light on the changes in penguin brains that accompanied their transition to water.

"Comparing multiple species (extinct and living and living birds that both fly and dive), in the way our study does, brings us closer to the answers of two major questions about penguin brain evolution: (1) what major morphological changes have occurred, (2) when did these changes occur?" said lead author Claudia Tambussi. The new finds, which are described in the latest issue of the Journal of Vertebrate Paleontology, include skulls which are so well-preserved that they could be CT-scanned to analyze their internal structure.

These scans revealed some interesting traits of these early penguins that speak to their transitional nature. Many of these findings have to do with the sensory abilities of these fossil species. For instance, one area, the Wulst, which is associated with complex visual functions, is enlarged. "The Antarctic fossils reveal that the neuroanatomy of penguins was still evolving roughly 30 million years after the loss of aerial flight, with trends such as the expansion of the Wulst and reduction of the olfactory bulbs still in progress", said co-author Daniel Ksepka.

In addition to the increase in visual complexity, and reduction in olfaction, findings in the ear region shed light on the head position and equilibrium-maintaining abilities of the fossil penguins. All together, the findings show that these early penguins had many of the adaptations of living forms, while having a few unique traits not seen in the modern ones. Not only that, but some of these adaptations are found in modern flying birds, attesting to penguins' unique mode of swimming.

In this gif, one of the Antarctic Eocene skulls is featured. The virtual brain is in blue: in red the right inner ear and carotids; in yellow the olfactory bulbs and some nerves. Credit: Journal of Vertebrate Paleontology
Said Ksepka, "Penguins are considered flightless, but when it comes to wing-propelled diving they are essentially practicing underwater flight. The brain morphology reflects this as penguins retain an overall "flight-ready" brain."

On Seymour Island emerges the La Meseta Formation, the most prolific localities for fossil penguin remains worldwide in terms of raw abundance. Credit: Journal of Vertebrate Paleontology

More information: Philipp ST, Kalisch T, Wachtler T, Dinse HR (2015) Enhanced tactile acuity through mental states. Sci. Rep. 5,13549; DOI: 10.1038/srep13549

Journal reference: Journal of Vertebrate Paleontology search and more info website
Provided by: Society of Vertebrate Paleontology search and more info


Monday, August 3, 2015

Shifting winds, ocean currents doubled endangered Galápagos penguin population

August 3, 2015
Shifting winds, ocean currents doubled endangered Galápagos penguin population
satellite image of the Galápagos Islands in 2002. Almost all of the Galápagos penguins live along the western coasts of Isabela and Fernandina, and two–thirds of the birds reside along the southwestern bulge of Isabela. Credit: Imagery NASA
Shifts in trade winds and ocean currents powered a resurgence of endangered Galápagos penguins over the past 30 years, according to a new study. These changes enlarged a cold pool of water the penguins rely on for food and breeding - an expansion that could continue as the climate changes over the coming decades, the study's authors said.
The Galápagos Islands, a chain of islands 1,000 kilometers (600 miles) west of mainland Ecuador, are home to the only in the Northern Hemisphere. The 48-centimeter (19-inch) tall black and white Galápagos penguins landed on the endangered species list in 2000 after the population plummeted to only a few hundred individuals and are now considered the rarest penguins in the world.

Most of the penguins live on the archipelago's westernmost islands, Isabela and Fernandina, where they feed on fish that live in a cold pool of water on the islands' southwestern coasts. The cold pool is fed by an , the Equatorial Undercurrent, which flows toward the islands from the west. When the current runs into Isabela and Fernandina, water surges upward, bringing cold, nutrient-rich water to the surface.

New research suggests shifts in wind currents over the past three decades, possibly due to climate change and natural variability, have nudged the Equatorial Undercurrent north. The changing current expanded the nutrient-rich, farther north along the coasts of the two islands, likely bolstering algae and fish numbers in the cold pool. This allowed the penguin population to double over the past 30 years, swelling to more than 1,000 birds by 2014, according to the new study.

Climate change could further shift wind patterns and ocean currents, expanding cold water further north along the coasts of Isabela and Fernandina and driving fish populations higher, according to the new study.

Penguins, as well as other animals like fur seals and marine iguanas that feed and reproduce near the cold waters, may increase in numbers as the northwestern coasts of the islands become more habitable, said the study's authors. They noted that wind and ocean currents could also return to earlier conditions, leading to a decline in penguin populations.

"The penguins are the innocent bystanders experiencing feast or famine depending on what the Equatorial Undercurrent is doing from year to year," said Kristopher Karnauskas, a climate scientist who performed the research while at Woods Hole Oceanographic Institution in Cape Cod, Massachusetts, and lead author of the new study recently accepted in Geophysical Research Letters, an American Geophysical Union journal.

The new findings could help inform conservation efforts to save the endangered penguins, said the study's authors. Increasing efforts on the northern coasts of the islands and expanding marine-protected areas north to where the penguins are now feeding and breeding could support population growth, the study's authors said.

Karnauskas notes that the vast majority of marine organisms will be negatively affected by the rise in ocean temperatures and acidification that are expected to occur across the globe as a result of climate change.

"With climate change, there are a lot of new and increasing stresses on ecosystems, but biology sometimes surprises us," said Karnauskas. "There might be places—little outposts—where ecosystems might thrive just by coincidence."

Galápagos penguins are the only Northern Hemisphere penguins.  
(Photo : Flickr: Aaron Logan) 

Penguin population changes

The Galápagos penguin population tenuously hangs onto the islands that so enthralled Charles Darwin during his visit in 1835. The penguins once numbered around 2,000 individuals, but in the early 1980s a strong El Niño - a time when sea surface temperatures in the tropical Pacific are unusually warm - brought their numbers down to less than 500 birds. Dogs, cats and rats introduced to the islands also stymied the penguin population by attacking the birds, disturbing their nests, and introducing new diseases, according to previous research.

Despite these setbacks, the penguins gradually increased in number in the following decades, according to local bird counts. Researchers, interested by the increase in penguins, noted that the birds remained near the coldest stretches of water. Nearly all of the Galápagos penguins live on the western coasts of Isabela and Fernandina, and two-thirds of them huddled near the coldest waters at the southern tips of the islands, according to previous research.

The study's authors wanted to know whether the growing numbers of penguins were related to local changes in ocean temperature. They combined previously-collected penguin population data from 1982 to 2014 with sea surface temperature data from satellites, ships and buoys for the same time period.

They found that the cold pool, where sea surface temperatures are below 22 degrees Celsius (71 degrees Fahrenheit), expanded 35 kilometers (22 miles) farther north than where it was located at the beginning of the study period. In the 1980s the cold water pocket reached only the southern halves of the western coasts of Isabela and Fernandina. By 2014, the cold water pocket extended across the entire western coasts of the islands.

Varying trade winds, ocean currents

A shift in and underwater ocean currents likely caused the Galápagos cold pool expansion, propose the authors.

Trade winds blow surface ocean waters from the southern side of the equator to the northern side of the equator. As surface waters pile up in the north, the water at the bottom of the pile is squished south, nudging the Equatorial Undercurrent - a cold current that flows roughly 50 meters (160 feet) under the ocean surface - south of the equator.

Likely due to a combination of natural variation and human-caused climate change, trade winds west of the Galápagos slackened during the study period, lessening the pressure pushing the Equatorial Undercurrent south, according to the new study. Consequently, the ocean current gradually shifted north, increasing the amount of cold water coming to the Galápagos Islands, according to the study's authors.

Satellite images showed that this expanded pool of cold water likely encouraged the growth of phytoplankton, according to the new study. This increase in ocean algae attracted fish to the area - the main entrée for Galápagos penguins, suggest the authors. The largest pulses of cold water reached the islands from July through December, coinciding with the penguins' breeding season. The bountiful fish helped the birds successfully reproduce and feed their young, according to the new study.

Models indicate trade winds will continue to abate in the future as the climate warms, Karnauskas said. This could cause the undercurrent to continue to move north, expanding the Galápagos cold pool and possibly further raising penguin populations, he said. Other animal populations like the endangered Galápagos fur seal and the marine iguana also may profit from the prolific amount of food in the Galápagos cold pool, according to the study's authors.

Wind and ocean currents could also possibly return to where they were in the 1980s, compressing the cold pool and possibly leading to a decline in penguins, Karnauskas added.

The new study shows how large-scale changes in the climate can act locally, said Michelle L'Heureux, a climate scientist with the National Oceanic and Atmospheric Administration's Climate Prediction Center in College Park, Maryland, and not an author on the new paper.

"While it is important that we focus on the big picture with , it's really the small scale that matters to the animals and plants that are impacted," she said.

More information: Geophysical Research Letters, 16 July 2015. DOI: 10.1002/2015GL064456

Journal reference: Geophysical Research Letters search and more info website
Provided by: American Geophysical Union search and more info website