Ooh, not a popular choice. Just 18% of my audience chose this. Surely there can’t really be a creature who pees through its mouth…?
The Chinese Soft-shelled Turtle (Pelodiscus sinensis)
Yeah, this is a weird one. Researchers noticed that even though these turtles are air-breathers, they still stick their heads under water for long periods at a time… Why? Turns out they were excreting – through their mouths.
It works like this. These turtles produce the same waste product we do, urea. We get rid of urea by processing it through our kidneys and flushing it out as urine – but this requires lots of water and is one of the reasons we humans need to drink so much. For the turtle, this isn’t an option. It lives in brackish, salty water that would eventually be toxic to drink.
Their solution is truly inspired. The chinese soft-shelled turtle only gargles the salty water and the urea dissolves into this mouthful… which the turtle then spits back out. It’s managed to bypass the need to drink lots of water to flush out urea! This incredible (and incredibly odd) adaptation has meant that these turtles have been able to move into brackish waters, which would otherwise be impossible for them to live in.
Ip, Y. K., Loong, A. M., Lee, S. M., Ong, J. L., Wong, W. P., & Chew, S. F. (2012). The Chinese soft-shelled turtle, Pelodiscus sinensis, excretes urea mainly through the mouth instead of the kidney. The Journal of experimental biology, 215(21), 3723-3733.