Glass frogs

Good short video on glass frogs which have transparent bellies so that you can see their organs including the heart. They also have translucent skin.

Video - Glass frogs: crystals of the rainforest
https://www.youtube.com/watch?v=BVFMtELtSic

also

New species of glass frog found in Costa Rican mountains
http://www.ticotimes.net/2015/04/15/new-species-of-glass-frog-discovered-in-costa-rican-mountains




Glass frog species range