Marine pufferfish contain tetrodotoxin (TTX), an extremely potent neurotoxin. 
All species of the genus Takifugu accumulate TTX in the liver and ovaries, 
although the tissue(s) in which it is localized can differ among species. TTX is 
the major defense strategy the pufferfish appears to use against predators. TTX 
is also used as a male-attracting pheromone during spawning. Here we demonstrate 
an additional (and unexpected) use of maternal TTX in the early larval stages of 
the Takifugu pufferfish. Predation experiments demonstrated that juveniles of 
all the species of fish used as predators ingested pufferfish larvae, but spat 
them out promptly. Liquid Chromatography-Tandem Mass Spectrometry (LC-MSMS) 
analysis revealed that the pufferfish larvae contain a small quantity of TTX, 
which is not enough to be lethal to the predators. Immunohistochemical analysis 
with anti-TTX monoclonal antibody revealed that the TTX is primarily localized 
in the body surface of the larvae as a layer of protection. Our study showed the 
female parent of the Takifugu pufferfish vertically transfers TTX to the larvae 
through its accumulation in the ovaries, and subsequent localization on the body 
surface of the larvae.