Neural tissue normally dies quickly without oxygen. Yet bird retinas—among the most energy-demanding tissues in the animal kingdom—function permanently without it. An international research team has now discovered how birds have solved this biological paradox. The scientists’ study showed that the inner parts of the bird retina operate under chronic oxygen deprivation, relying instead on anaerobic energy production. Their findings also overturn a long-standing assumption about a mysterious structure in the bird eye—the pecten oculi—that has puzzled scientists since the 17th century. The collective findings may be relevant in future treatment of stroke patients, the authors suggest. “In conditions like stroke, human tissues suffer because oxygen delivery is reduced and metabolic waste accumulates,” said Jens Randel Nyengaard, MD, PhD, professor in the department of clinical medicine at Aarhus University. “In the bird retina, we see a system that copes with oxygen deprivation in a completely different way.” Nyengaard is senior author of the team’s published paper in Nature, titled “Oxygen-free metabolism in the bird inner retina supported by the pecten.” The extraordinarily high metabolism of neural tissues in warm-blooded animals requires a continuous and ample supply of oxygen and nutrients to support aerobic metabolism, the authors wrote. Most animals supply neural tissue with oxygen through dense networks of tiny blood vessels. “Neural tissues are exceptionally sensitive to oxygen deprivation and rely on a dense network of blood vessels to support their extraordinarily high metabolic demands for oxygen, nutrients and clearance of waste products.” The retina, a highly specialized extension of…
