edible frog tadpole

Species: Pelophylax „esculentus“ (hybrid)

english: edible frog/ common frog/ green frog
deutsch: Teichfrosch
norsk: hybridfrosk, spiselig frosk

Location: Streitköpflesee Linkenheim (Baden-Württemberg -> Germany)
Date: 14th July 2013

During a dive I found a lot of tadpoles. But they didnt looked like normal tadpoles. Their bodys were such big as an chicken-egg. I have never seen before such huge tadpoles. At some websites I read about hormonally disturbed tadpoles. If they grow up and change into frogs, they shrink into normal size of a edible frog. 
The edible frog is a natural hybrid between the marsh frog (Pelophylax ridibundus) and the pool frog (Pelophylax lessonae).