A team of biologists led by Dr Yuen Ip of the National University of Singapore has discovered that Chinese soft-shelled turtles, Pelodiscus sinensis, effectively urinate through mouth.
Chinese soft-shelled turtles are exquisitely adapted to their aquatic lifestyle, sitting contentedly on the bottom of brackish muddy swamps or snorkelling at the surface to breath. They even immerse their heads in puddles when their swampy homes dry up. Why do these air-breathing turtles submerge their heads when they mainly depend on their lungs to breathe and are unlikely to breathe in water? Given that some fish excrete waste nitrogen as urea and expel the urea through their gills, the team wondered whether the turtles were plunging their heads into water to excrete waste urea through their mouths, where they have strange gill-like projections.