Archive for December 2015
A recent study suggests penguins may have a poorly developed sense of taste. This is not to be confused with tasting bad – which accounts by sailors forced to survive on penguin meat suggest is also true. Rather, new research suggests penguins lack the ability to detect sweet or savory tastes.
Humans perceive 5 basic categories of taste: sweet, sour, salty, bitter, and umami (which might best be described as savory). However, evidence suggests penguins are limited to just sour and salty. Researchers came to this conclusion after combing through recently assembled genomes from two penguin species. A mutation in the umami taste receptor gene Tas1r1 causes it not to function properly in penguins. Tasr2r genes, responsible for bitter reception, are non-functional in penguins too. Penguins also lack the taste receptor gene Tas1r2, which is associated with sweetness detection. These factors would preclude them from enjoying, say, a Shake Shack burger or a candy apple. Penguins are not alone in lacking the ability to taste sweet – Tas1r2 appears to be absent in all birds, though nectar-loving hummingbirds seem to have repurposed Tas1r1 to detect sweetness.
Are penguins hindered by their diminished sense of taste? Probably not. As the authors note, penguins swallow their food whole, so they might not benefit too much from telling whether or not it tastes good. Truth be told though, I have certainly known a few aquarium penguins who strongly prefer one type of fish to another when it comes to their dinner – so much so that their keepers serve the less desirable portion first while they are still hungry.
There is one aspect of the study that clashes with paleontological evidence. The authors conclude the loss of some tastes may be related to the origin of penguins in Antarctica. However, when one considers the complete penguin family tree including the many extinct species, it is far more likely penguins originated at lower latitudes when climate was much warmer and invaded icy Antarctica late in their history.
One exciting extension of the research is that we now have a reason to test the conclusions in the real world. Perhaps some biologists are now hatching a plan to tempt penguins with sour pickles, salty chips, or sweet pieces of candy to see if they can indeed tell the difference.
Reference: Zhao, H., J. Li, and J Zhang. 2015. Molecular evidence for the loss of three basic tastes in penguins. Current Biology 25 :R141 – R142