Do birds have a good sense of smell?(ize of the olfactory bulb. Wide variati...)

Date:7/16/2008

ize of the olfactory bulb." Wide variation in numbers of OR genes, and sizes of olfactory bulbs, has also been found amongst mammals. The implication of this finding is that different ecological niches may have shaped the OR gene repertoire sizes in birds, as has been suggested for mammals. The high number of OR genes in the kiwi could be explained by this bird's unusual ecological niche. Unique among birds, the nostrils of the night-active kiwi are at the tip of the bill. When kiwis probe the forest floor in search of food, they are guided by smell rather than sight. Indeed the snuffling, nocturnal kiwis are sometimes considered to be New Zealand's equivalent of a hedgehog!

Besides the total number of OR genes, the researchers estimated which proportion of these genes are functional. This was done because, in mammals, a reduced dependence on the sense of smell is associated with OR genes gradually accumulating mutations and so becoming non-functional. For example, in humans, which have a poor sense of smell compared with most other mammals, only about 40% of all OR genes may be functional. However, in the bird species studied by Steiger et al., the large majority of the OR genes were functional, again indicating that the sense of smell is much more important in birds than previously thought.

From the analysis of the chicken genome three years ago a new class of OR genes was found. Now Silke Steiger and her colleagues have shown that this class of genes seems to be a shared feature of all birds, while such OR genes are not found in other vertebrates such as fish, mammals or reptiles. The specific function of this class of bird-specific OR genes remains unknown.

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Contact: Silke Steiger steiger@orn.mpg.de 49-815-793-2416 Max-Planck-Gesellschaft Source:Eurekalert

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