Abstract
Tetrodotoxin (TTX) is a potent neurotoxin responsible for many human intoxications globally. Despite its potency and widespread occurrence in taxonomically diverse species, the primary source of TTX remains uncertain. Paphies australis, an endemic clam found in New Zealand, has been found to contain TTX in several locations. However, it is unknown if this represents endogenous production or accumulation from an external source. To address this question, the concentrations of TTX in whole P. australis and dissected organs (siphons, foot, digestive gland and the ‘rest’) from thirteen sites around New Zealand were determined using liquid chromatography-tandem quadrupole mass spectrometry analysis (LC-MS/MS). Depuration rate of TTX was also investigated by harvesting and measuring concentrations in P. australis maintained in captivity on a toxin-free diet every three to 15 days for 150 days. The LC-MS/MS analyses of the spatial samples showed that TTX was present in P. australis from all regions tested, with significantly (p < 0.001) higher concentrations (15–50 μg kg−1) observed at lower latitudes of the North Island compared with trace levels (0.5–3 μg kg−1) in the South Island of New Zealand. Tetrodotoxin was detected in all the dissected organs but the siphons contained the highest concentrations of TTX at all sites analysed. A linear model of the depuration data identified a significant (p < 0.001) decline in total TTX concentrations in P. australis over the study period. The siphons maintained the highest amount of TTX across the entire depuration study. The digestive glands contained low concentrations at the start of the experiment, but this depurated rapidly and only traces remained after 21 days. These results provide evidence to suggest that P. australis does not produce TTX endogenously but obtains the neurotoxin from an exogenous source (e.g., diet) with the source more prevalent in warmer northern waters. The association of higher TTX concentrations in shellfish with warmer environments raises concerns that this toxin's distribution and abundance could become an increasing human health issue with global warming.
Highlights
Tetrodotoxin (TTX) is a potent neurotoxin that blocks voltage-gated sodium channels (Noguchi and Ebesu, 2001)
Tetrodotoxin was predominantly found in tropical regions (Lange, 1990) but in recent years, it has been detected in a greater number of species from temperate regions including: bivalves from the Mediterranean Sea (Vlamis et al, 2015) and England (Turner et al, 2015); and bivalves, gastropods and platyhelminths in New Zealand (McNabb et al, 2010; Salvitti et al, 2015)
Tetrodotoxin was detected in P. australis from all sites around New Zealand (Fig. 2)
Summary
Tetrodotoxin (TTX) is a potent neurotoxin that blocks voltage-gated sodium channels (Noguchi and Ebesu, 2001). It has been responsible for up to 100 human intoxications per annum (Isbister and Kiernan, 2005; Tsuda et al, 1964). It is named after the pufferfish family, Tetraodontiformes, from which it was first identified and isolated (Chau et al, 2011). Tetrodotoxin was predominantly found in tropical regions (Lange, 1990) but in recent years, it has been detected in a greater number of species from temperate regions including: bivalves from the Mediterranean Sea (Vlamis et al, 2015) and England (Turner et al, 2015); and bivalves, gastropods and platyhelminths in New Zealand (McNabb et al, 2010; Salvitti et al, 2015). Increasing reports of TTX in farmed aquaculture species, such as bivalves, has drawn attention to the toxin, reinvigorating scientific interest and regulatory concerns (Knutsen et al, 2017)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
