Board Thread:Naruto Discussions/@comment-30168130-20161009021213/@comment-1512913-20161010042432

No, it's both. Jugo Clan's Kekkei Genkai comes in 2 parts: Jiraiya's form wasn't Sage Transformation.
 * passive absorption of natural energy
 * enzyme in their bodily fluids that in exposure to natural energy/senjutsu chakra reacts and triggers a transformation, called Sage Transformation.