Corryn Wetzel in New Scientist:
Glass frogs can boost their transparency by up to 61 per cent by storing most of their blood in their liver while they sleep. Researchers hope that understanding how the frogs manage to pool their blood this way without experiencing blood clots could provide new insights into preventing dangerous clots in other animals, including humans.
The tropical, marshmallow-sized amphibians spend their days sleeping on bright green leaves and foraging for food under the cover of dark. Being semi-see-through helps glass frogs avoid being spotted by predators, but it’s a challenging biological task, as most animals need to continuously pump red blood cells throughout their body to deliver oxygen to their tissues.
More here.