Tissue-Specific Distribution of Tetrodotoxin (TTX) and Its Analogues in the Blue-Lined Octopus <i>Hapalochlaena fasciata</i> Hoyle 1886 Collected from Jeju Island, Korea using LC-MS/MS

Abstract

Endemic to southern Australia, the highly venomous octopus Hapalochlaena fasciata has extended its distribution range to temperate areas including Korea, raising concern for potential poisoning risks associated with consuming or encountering these tetrodotoxin (TTX)-bearing octopuses. We assessed TTX and its analogues in blue-lined octopuses occurring on Jeju Island, Korea using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The mitochondrial 16S ribosomal RNA (16S rRNA) and cytochrome oxidase subunit I (COI) sequences analysis revealed that the octopus specimens collected from Jeju Island were H. fasciata. The immunohistochemistry revealed that TTX is mostly distributed in the posterior salivary gland (PSG). In the LC-MS/MS, the PSG showed the highest content of TTX, ranging from 259.4 to 883.5 mu g/g, which was several hundred times higher than the levels observed from the skin (2.5-32.0 mu g/g) and arms and mantle (2.9-19.0 mu g/g). Using LC-Orbitrap MS, we also identified and quantified the TTX analogues. High concentrations of TTX analogues were confirmed in PSG, showing a parallel to the presence of TTX. In PSG, deoxyTTXs (343 +/- 269 mu g/g) were found to be highest, followed by dideoxyTTX (144 +/- 96 mu g/g), 4-epiTTX (21.1 +/- 12.3 mu g/g), trideoxyTTX (14.4 +/- 28.8 mu g/g), and anhydroTTX (6.82 +/- 3.86 mu g/g). The levels of TTX and its analogues found in H. fasciata specimens collected from Jeju Island were comparable to those reported in venomous octopuses from tropical and subtropical areas. As sea surface temperatures (SST) rise in temperate regions, there is a potential for an increase in the prevalence of venomous octopuses. Therefore, conducting regular surveillance of such toxic organisms is imperative to ensure public health safety and effective management strategies.