The invasive sea slug Pleurobranchaea maculata is a vector of two potent neurotoxins in coasts of Argentina.
Toxic exotic organisms can have profound effect as new vectors of keystone compounds in non-native areas. In recent years the invasive sea slug Pleurobranchaea maculata has been reported as thriving along the oriental coasts of South America. The same species had been previously found to contain high levels of tetrodotoxins (TTXs) in its native range. With the aim of determining toxin contents for the introduced individuals we performed mouse bioassays (MBA) and liquid chromatography tandem-mass spectrometry analyses (LC-MS/MS) in three distant populations (-38°02′11″, -57°31′28″; -40°29′59″, -60°14′09″; -42°44′15″, -65°01′40″) and followed the temporal variation in toxin contents in one of them, from June 2014 to January 2015. Relative low levels of TTXs were detected jointly with high levels of PSTs. This is the first identification of TTXs in the temperate coasts of the southwestern Atlantic and the first detection of PSTs in a pleurobranch, in both adults and eggs. Concentrations of PSTs and TTXs varied widely among individuals and populations, and through time. Our results provide new hints on the origin and acquisition mechanisms of these toxins in P. maculata and highlight the risk posed by the introduction of this new vector of potent neurotoxins for seafood safety and marine communities in the invaded area.