Role of maternal tetrodotoxin in survival of larval pufferfish.

It is known that tetrodotoxin (TTX), also known as pufferfish toxin, is an extremely potent neurotoxin and had been detected in various taxa. However, the exact function of the toxin in TTX-bearing organisms has remained unclear. In Takifugu pufferfish species, it has been suggested that TTX is utilized to protect larvae from predators but no experimental proof exists. In the present study, we used pufferfish Takifugu alboplumbeus larvae from wild and cultured parents to determine the effects of the maternal TTX on the survival of toxic and non-toxic pufferfish larvae, respectively. TTX contents in the larval pufferfish differed between the larvae derived from wild and cultured parents (1.23 ± 0.20 ng/individual vs. undetectable levels, respectively). Immunohistochemical staining with anti-TTX monoclonal antibody demonstrated that the TTX-specific signals were primarily observed at the body surface of the larvae of wild parents, but not of cultured parents. Predation experiments demonstrated that the juveniles of Girella punctata and Chaenogobius gulosus, used as predator fish, ingested the pufferfish larvae derived from either type of parents, but instantly spat out those from wild parents only. These results indicate that larvae, which are at the most vulnerable stage in the life of pufferfish, are protected by maternal TTX.