Contrasting Toxin Selectivity between the Marine Pufferfish Takifugu pardalis and the Freshwater Pufferfish Pao suvattii

Abstract

To clarify the differences in toxin selectivity between marine and freshwater pufferfish, we conducted experiments in artificially reared nontoxic specimens of Takifugu pardalis (marine) and Pao suvattii (freshwater) using tetrodotoxin (TTX) and paralytic shellfish poison (PSP; decarbamoylsaxitoxin (dcSTX) or saxitoxin (STX)). T. pardalis specimens were administered feed homogenate containing TTX or dcSTX (dose of toxin, 55.2 nmol/fish) and P. suvattii specimens were administered feed homogenate containing TTX + STX (dose of each toxin, 19.2 nmol/fish) by oral gavage. The toxin content in the intestine, muscle, skin, liver, and gonads was quantified after 24 and 48 or 72 h. In T. pardalis, TTX administered into the intestine was absorbed into the body and transferred and retained mainly in the skin and liver, while dcSTX was hardly retained in the body, although it partly remained in the intestine. In strong contrast, in P. suvattii, little TTX remained in the body, whereas STX was absorbed into the body and was transferred and retained in the ovary and skin. The findings revealed that TTX/PSP selectivity differs between the marine species T. pardalis and the freshwater species P. suvattii. T. pardalis, which naturally harbors TTX, selectively accumulates TTX, and P. suvattii, which naturally harbors PSP, selectively accumulates PSP.

Co-Occurrence of Tetrodotoxin and Saxitoxins and Their Intra-Body Distribution in the Pufferfish Canthigaster valentini

“…Toxins were extracted from the muscle, liver, intestine, gallbladder, and gonads of four male and six female C. valentini specimens ( Table 1 ) collected from Amami-Oshima Island in the Kagoshima Prefecture of Japan. Analysis of the extracts by liquid chromatography tandem mass spectrometry (LC-MS/MS) for TTX [ 9 , 26 ] revealed that samples from all tissues produced a peak with a retention time corresponding to that of the TTX standard in the chromatogram monitored at m / z 162 as a product ion with m / z 320 as a precursor ion (described as m / z 320 > 162 hereafter; a typical chromatogram is shown in Figure 2 ). Although TTX analogues were not included in the analysis because no standards were available, peaks estimated to be 4- epi TTX, 4,9-anhydroTTX, 11-deoxyTTX, and 11-oxoTTX were observed at m / z 320 > 162, 302 > 162, 304 > 162, and 336 > 162, respectively (typical chromatograms are shown in Figure A1 ).…”

“…The peak intensities suggested that 4- epi TTX, 4,9-anhydroTTX, and 11-deoxyTTX were present in small amounts, while 11-oxoTTX was present at a higher level. When the same extracts were analyzed by high-performance liquid chromatography with post-column fluorescence derivatization (HPLC-FLD) for STXs [ 26 , 27 ], samples from each tissue, except for the female gallbladder, produced peaks at the retention times corresponding to those of neoSTX, decarbamoylSTX (dcSTX), and STX standards (a typical chromatogram is shown in Figure 3 ). No known components, such as C toxins and gonyautoxins (GTXs), were detected (data not shown).…”

“…In a recent in vivo TTX/STX administration experiment using nontoxic cultured individuals, Gao et al [ 26 ] found that T. pardalis , which possesses TTX in nature, selectively accumulates TTX, and P. suvattii , which possesses STXs in nature, selectively accumulates STXs. In other words, the ratio of TTX/STX harbored by pufferfish is presumed to more strongly depend on the inherent TTX/STX selectivity of pufferfish than the prevalence of TTX/STX in prey organisms, but the molecular mechanisms remain to be elucidated.…”

“…Each tissue of the C. valentini specimens was extracted with 0.1% acetic acid [ 28 ], passed through an HLC-DISK membrane filter (0.45 µm, Kanto Chemical Co., Inc., Tokyo, Japan), and subjected to LC-MS/MS for TTX [ 9 , 26 ] and HPLC-FLD for STXs [ 26 , 27 ].…”

Tetrodotoxin functions as a stress relieving substance in juvenile tiger puffer Takifugu rubripes

“…Then, the extract was partially purified with Bio-Gel P-2 column (Bio-Rad Laboratories Inc., Hercules, CA, USA) and the absorbed TTX was eluted with 0.05 M AcOH from the gel. The TTX fraction was analyzed by LC/MS/MS according to the method described by Nakashima et al (2004) and Gao et al (2019).…”