Temporal and Population-level Variation of Tetrodotoxin in Hong Kong Newt (Paramesotriton hongkongensis)

Newts from the family Salamandridae possess a potent neurotoxin - tetrodotoxin (TTX). The levels of TTX have been studied intensively, aiming to reveal the function and origin of TTX in this family. Research has found within- and between-population variations in North American newts like Taricha, which is possibly related to several life history traits (e.g. sex and life stage) or co-evolution with its predator. However, our knowledge about TTX levels in the Asian newt clade is relatively limited. To fill this gap, we investigated the variation of TTX levels in Hong Kong newt (Paramesotriton hongkongensis) and explored its ecological context with reproduction status, sex, population, life stage, and body condition. We collected 931 skin biopsy samples from six populations, of which 831 were from the breeding season and 100 were from the non-breeding season. Preliminary results show male newts have a higher level of TTX in the breeding season compared to the non-breeding season while females do not. However, the inter-sex difference is only prominent in the non-breeding season, with the TTX level being roughly four times higher in the female newts. Additionally, TTX level differs significantly between breeding populations. We also found higher TTX correlates with lower body condition. Overall, these outcomes illustrate the variability of TTX in P. hongkongensis at the population level and contribute to a better understanding of the ecology of TTX for Asian salamanders.