guano
I was recently reading a forum in which someone claimed that the tapetum lucidum of the human eye is responsible for red-eye in photos. The tapetum lucidum, latin for "bright carpet," is a reflective layer at the back of the eyes in many animals -- but not humans. Based on other web sites (besides that forum), it seems that the human red-eye effect is due rather to a quick flash not giving our pupils time to adjust, so that light is focused and reflected off the blood vessels of our retina.
However, what I found interesting was that guanine crystals play a significant role in the reflective property of some animals' tepeta lucida. The name for guanine (C5H5N5O) derives from "guano" which comes from Quechua (language of the Incas) as the Spanish word for "compost" -- id est, poop and/or fertilizer. In English, guano is specifically bat poop. Guanine is named after guano since that is the material whence guanine was first isolated (in 1844 according to wikipedia).
Guanine is also famous as one of the four nucleobases (along with adenine, cytosine and thymine (uracil in RNA)) in DNA.
This made me think: why is there so much guanine in bat poop? And here is a theory: perhaps, evolutionarily, bats once relied on their vision much more heavily. In that case, a layer of highly reflective material on the floor of a cave would certainly help in identifying your prey (such as a flying insect) at dusk or dawn.
What do you think? Anybody know a better reason why guano has so much guanine?
However, what I found interesting was that guanine crystals play a significant role in the reflective property of some animals' tepeta lucida. The name for guanine (C5H5N5O) derives from "guano" which comes from Quechua (language of the Incas) as the Spanish word for "compost" -- id est, poop and/or fertilizer. In English, guano is specifically bat poop. Guanine is named after guano since that is the material whence guanine was first isolated (in 1844 according to wikipedia).
Guanine is also famous as one of the four nucleobases (along with adenine, cytosine and thymine (uracil in RNA)) in DNA.
This made me think: why is there so much guanine in bat poop? And here is a theory: perhaps, evolutionarily, bats once relied on their vision much more heavily. In that case, a layer of highly reflective material on the floor of a cave would certainly help in identifying your prey (such as a flying insect) at dusk or dawn.
What do you think? Anybody know a better reason why guano has so much guanine?
posted by Tyler | 3:39 PM
2 Comments:
Update: My friend Allison points out that not all bats live in caves. Much as Calvin must have felt when he first discovered that bats aren't bugs, my otherwise impressive hypothesizing has certainly been deflated a bit.
Good point Allison!
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