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There is none, generally the Red-Bellied Piranha is the "regular Piranha"
No. Even though people may think it is the red bellied piranha it is actually the more unknown one; The black piranha.
Yes a piranha has a backbone.
All fish have backbones.
All piranhas, including red bellied piranhas, are not amphibians, they are fish.
Yes it does yo moma