Northern Gannet anatomy-an unexplained phenomena

28 01 2009

Yesterday, here at the Tufts Wildlife Clinic, researcher Jennifer Modrell gave a presentation on an anatomical structure that appears to be unique to Northern Gannets and their other gannet cousins.

Northern Gannet presented to SEANET for necropsy

Northern Gannet presented to SEANET for necropsy

While performing routine necropsies on gannets submitted to SEANET, Jen found an odd structure associated with the trachea (windpipe) in all the gannets she examined. Two prominent, yellow-orange, roughly spherical bodies arose from either side of the syrinx (which is the avian equivalent of the voicebox). Intrigued by these structures, Jen set out to learn more. She soon discovered that while occasional scientists back to the 1800s had observed and remarked upon the structures, no one had any idea what their purpose could be. Were they strange thyroid glands? A bizarre version of an immune organ known as the thymus? The literature was surprisingly sparse and Jen realized that she was in a position to answer a question at least 200 years old.

Her first goals were simple: to determine whether or not all Northern Gannets possess these structures and whether they are present in all ages of gannet. The simple answer to both was yes, though they are considerably smaller in immature birds.

The Northern Gannet trachea (pale structure running from the left side to the middle of photo) splits into two bronchi at the middle of the photo. At this split, known as the syrinx, two yellow spherical structures are observed attached. Their function remains uncertain.

The Northern Gannet trachea (pale structure running from the left side to the middle of photo) splits into two bronchi at the middle of the photo. At this split, known as the syrinx, two yellow spherical structures are observed attached. Their function remains uncertain.

Jen theorized that the structures may modify the sound of the birds’ voices, and may be used to signal sexual maturity or even health.  She partnered with a Tufts pathologist, Dr. John Keating, to determine the microscopic makeup of the nodules. That investigation showed that the nodules are comprised of fat with a generous blood supply. Interestingly, Jen has also found that even in birds severely weakened from starvation, these fatty nodules are maintained, even when all other fat stores in the body have been depleted. This suggests that the nodules are very important to the bird, and may in fact be vital to breeding successfully–a prospect even very ill birds will often pursue to ensure the survival of their genetic material in future generations.

Jen intends to continue her research into the role these bizarre structures play in the life history of the Northern Gannet. SEANET is proud to have helped Jen even in a minor way with this valuable project, and we look forward to future developments in her investigations.


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