Navigation Links
Finding is a feather in the cap for researchers studying birds' big, powerful eyes

BETHESDA, Md., June 23, 2011 Say what you will about bird brains, but our feathered friends sure have us -- and all the other animals on the planet -- beat in the vision department, and that has a bit to do with how their brains develop.

Consider the in-flight feats of birds of prey: They must spot their dinner from long distances and dive-bomb those moving targets at lightning speed. And then there are the owls, which operate nimbly on even the darkest nights to secure supper in swift swoops. Some birds have ultraviolet sensitivity; others have infrared sensitivity. To boot, some birds can even see the Earth's magnetic field.

Much of the credit for avian visual acuity goes to the extraordinary retina, which grows out of the brain during development, making it an official component of the central nervous system. Indeed, the avian retina is far more complex in structure and composition than the human retina, and it contains many more photoreceptors -- rod- and cone-shaped cells that detect light and color, respectively.

While researchers over the years have come to better understand much about the avian retina, many nagging questions remain. For Thorsten Burmester's research team at the University of Hamburg, the question was this: How does such a productive retina sustain itself when the avian eye has very few capillaries to deliver oxygen to it? After all, it has to "breathe," so to speak.

"The visual process in the vertebrate eye requires high amounts of metabolic energy and thus oxygen," Burmester's group writes in this week's Journal of Biological Chemistry. "Oxygen supply of the avian retina is a challenging task because birds have large eyes, thick retinas and high metabolic rates, but neither deep retinal nor superficial capillaries."

To answer the question, Burmester's team took a closer look at a protein that they discovered exists in large quantities in photoreceptor cells of the avian eye -- and only of the avian eye. They named the protein globin E. (The "E" is short for "eye," of course.)

Burmester's team used a number of techniques to characterize globin E and found that it is responsible for storing and delivering oxygen to the retina.

The finding is intriguing for a number of reasons.

Firstly, it helps explain how birds evolved to have such large eyes, relative to their body mass, without a dense network of ocular capillaries for blood delivery. (Some owls, for instance, have bigger eyes than humans.)

"The exact origin of globin E is still somewhat a mystery," Burmester said. "It clearly evolved from some type of globin, but it has no obvious relative outside the birds."

The globins are all thought to share a common ancestor, and the most well-known members of the family are myoglobin and hemoglobin. Myoglobin is responsible for oxygen storage and release in heart and skeletal muscle fibers. Hemoglobin, meanwhile, transports oxygen from the lungs to other parts of the body in red blood cells.

Burmester explains: "Bird eyes have evolved to have a system not unlike those in our heart, which uses myoglobin to store and release oxygen to maintain respiration and energy-consumption during muscle contraction. In eyes, oxygen and energy are needed to generate neuronal signals."

Secondly, the finding puts to rest an earlier hypothesis that another molecule, neuroglobin, might be the oxygen-delivery vehicle for the avian eye. Neuroglobin is known to deliver oxygen to brain tissue, so it was only natural to suspect it. But it turns out that the messenger RNA fingerprint of globin E was 100-fold more prevalent than that of neuroglobin in Burmester's chicken retina samples, indicating that neuroglobin probably has another, yet-to-be defined function in the avian eye.

Lastly, globin E is another interesting illustration of the convergent evolution of "myoglobin-like" molecules. Among the organisms with proteins with similar functions are the soybean, which needs its leghemoglobin to deliver oxygen to the Rhizobium soil bacteria that colonize in root nodules, and the 2-foot-long sea worm Cerebratulus lacteus, which needs its mini-hemoglobin to keep its brain and neurons oxygenated when it burrows deep into the sea floor, where oxygen levels are low, in search of clams.


Contact: Angela Hopp
American Society for Biochemistry and Molecular Biology

Related biology news :

1. Plant pathologist finding Kansas wheat fields a molecular battleground this season
2. Researchers improve method for finding genetic mistakes that fuel cancer
3. Surprising findings from studies of spontaneous brain activity
4. Rochester autism researchers present new findings at IMFAR
5. TGen findings contribute to understanding of diabetic kidney disease
6. Findings may help keep pancreatic disease off the menu
7. Finding shows potential way to protect neurons in Parkinsons, Alzheimers, ALS
8. Finding a way to extend tomato shelf-life
9. Saint Louis University findings: Dont pitch stockpiled avian flu vaccine
10. New findings in Indias Bt cotton controversy: Good for the field, bad for the farm?
11. New findings provide cost, benefit data for Florida citrus industry
Post Your Comments:
(Date:10/27/2015)... -- Munich, Germany , October ... automatically maps data from mobile eye tracking videos created ... that they can be quantitatively analyzed with SMI,s analysis ... , October 28-29, 2015. SMI,s Automated Semantic Gaze ... tracking videos created with SMI,s Eye Tracking Glasses ...
(Date:10/26/2015)... India , October 26, 2015 ... --> adds ... 2015 to 2021 as well as ... 2015-2019 research reports to its collection ... . --> ...
(Date:10/26/2015)... Calif. , Oct. 26, 2015  Delta ID ... biometric authentication to mobile and PC devices, announced its ... smartphone, the arrows NX F-02H launched by NTT DOCOMO, ... NX F-02H is the second smartphone to include iris ... technology in ARROWS NX F-04G in May 2015, world,s ...
Breaking Biology News(10 mins):
(Date:12/1/2015)... , Dec. 1, 2015  Symic, a clinical-stage ... the extracellular matrix (ECM), today announced that it has ... advance the company,s pipeline, including its lead candidates SB-030 ... and includes the participation by all existing major investors, ... brings the total capital raised by Symic to over ...
(Date:12/1/2015)... 1, 2015 Dr. Harry Lander , President of Regen, ... Chief Science Officer and recruits five distinguished ... , President of Regen, expands his role to include ... recruits five distinguished scientists to join advisory team ... his role to include serving as Chief ...
(Date:12/1/2015)... (PRWEB) , ... December 01, 2015 , ... Matthew “Tex” ... new post, VerMilyea will oversee all IVF lab procedures as well as ... fertility preservation. , “We traveled 7,305 miles to Auckland, New Zealand to bring home ...
(Date:11/30/2015)... ... 2015 , ... Global Stem Cells Group Chile ... Central America and abroad for the first Iberoamerican Convention on Aesthetic Medicine, Cosmetology ... Testart will present and discuss new trends in anti-aging stem cell treatments, regenerative ...
Breaking Biology Technology: