Three puffafish in display case

When in danger, Puffafish puff themselves up to frighten their attacker. They do it by accumulating air or water in their oesophagus until it takes on a spherical form. They accumulate a toxin, called tetrodotoxine, in their bodies, apart from their muscles which make them fatally poisonous. This toxin is thus an additional weapon, to deter predators.