Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Penguins continue diving long after muscles run out of oxygen

12.05.2011
Breathing heavily at the edge of an ice hole, an Antarctic emperor penguin prepares to dive. Taking a last gulp of air, the bird descends and may not emerge again for another 20 minutes.

The penguin initially carries sufficient oxygen in three stores – the blood, lungs and myoglobin in muscle – to sustain aerobic metabolism. However, around 5.6 minutes after leaving the surface, lactate begins appearing in the penguin's blood and the bird crosses the so-called 'aerobic dive limit', switching to anaerobic metabolism in some tissues. So what triggers this transition?

Cassondra Williams from the Scripps Institution of Oceanography explains that the animals were thought to cross the aerobic dive limit when one of their three oxygen stores became exhausted. However, when Paul Ponganis measured oxygen levels in the blood and lungs of penguins after long dives, the animals had oxygen to spare. That only left the muscle as the potential trigger.

Williams explains that diving animals were thought to isolate their muscle from the circulatory system, leaving oxygen stored in the tissue as its only source of aerobic metabolism while submerged and forcing it to switch to anaerobic respiration once the supply was exhausted. So, she and Ponganis teamed up with Jessica Meir to travel to Antarctica to measure muscle oxygen levels in diving emperor penguin muscles and they publish their discovery that depleted muscle oxygen supplies trigger the aerobic dive limit in The Journal of Experimental Biology at http://jeb.biologists.org/content/214/11/1802.abstract.

However, before their departure, Williams had to design a near-infrared spectrophotometer to record the penguins' muscle oxygen stores as they dived in the wild. After two trying years of technical development and testing, Williams was able to travel south with her colleagues to surgically implant the spectrophotometers in the pectoralis muscles of emperor penguins. They also attached time–depth recorders to the animals' backs to track their dive profiles. Finally, the team ensured that the animals would return with their precious equipment by drilling an isolated hole in the sea ice – to which the penguins were guaranteed to return – before releasing the implanted animals to go foraging for a day or two.

After successfully retrieving all of the spectrophotometers and dive recorders and returning the penguins to their colony, Williams began analysing the data and found that the penguins had been actively foraging beneath the ice. Of the 50 dives that Williams successfully recorded, 31 exceeded the emperor penguin's calculated dive limit.

Next, Williams plotted the muscle oxygen profiles over the course of each dive and identified two distinct patterns. In the first, the oxygen levels fell continually, approaching zero around the point when the birds crossed the aerobic dive limit. Williams says, 'This profile certainly supports the hypothesis that muscle oxygen depletion is the trigger of the aerobic dive limit.'

However, when the team saw the second pattern, they were surprised that, after initially falling, the oxygen levels plateaued for several minutes before falling again to almost zero. They realised that blood must be flowing into the muscle to replenish the oxygen supply during the middle phase of the dive, delaying the onset of the aerobic dive limit.

Finally, having confirmed that the dive muscles are the source of the aerobic dive limit, Williams calculated the muscle oxygen consumption rate for dives with the first oxygen depletion pattern and was amazed to see that it was only 12.4ml of oxygen per kg of muscle per minute: 1/10th the value calculated for penguins swimming in an artificial flume and only 2 times their resting metabolic rate. 'I think this metabolic rate is impressive. You can see how hard they are working underwater but they are efficient swimmers and very hydrodynamic,' says Williams.

IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org

REFERENCE: Williams, C. L., Meir, J. U. and Ponganis, P. J. (2011). What triggers the aerobic dive limit? Patterns of muscle oxygen depletion during dives of emperor penguins. J. Exp. Biol. 214, 1802-1812.

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT permissions@biologists.com

Kathryn Knight | EurekAlert!
Further information:
http://www.biologists.com
http://jeb.biologists.org

More articles from Life Sciences:

nachricht When Air is in Short Supply - Shedding light on plant stress reactions when oxygen runs short
23.03.2017 | Institut für Pflanzenbiochemie

nachricht WPI team grows heart tissue on spinach leaves
23.03.2017 | Worcester Polytechnic Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

When Air is in Short Supply - Shedding light on plant stress reactions when oxygen runs short

23.03.2017 | Life Sciences

Researchers use light to remotely control curvature of plastics

23.03.2017 | Power and Electrical Engineering

Sea ice extent sinks to record lows at both poles

23.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>