This finding challenges the previous belief that toxin concentrations remain consistent throughout a newt’s lifetime and that males and females possess similar toxin levels. The study, conducted by Dr. Gary Bucciarelli from the University of California Davis, sheds light on the sexual dimorphism in toxin production among these amphibians.
Sexual Dimorphism in Toxin Production: Sexually dimorphic traits, such as coloration or physical characteristics, often play a crucial role in survival and reproductive fitness in sexually-reproducing animals. To investigate whether toxin production exhibits sexual dimorphism in newts, researchers collected samples from over 850 newts across 38 locations in California. They recorded various characteristics, including sex, size, mass, tail height, and whether female newts were pregnant.
Female Newts Carry More Toxin: The analysis revealed that female newts carried higher toxin levels than their male counterparts. While toxin levels in males remained relatively consistent, female newts exhibited greater fluctuations in toxin concentrations, potentially driven by factors like mate selection. These findings indicate that female newts are more poisonous than males, presenting a significant threat to potential predators.
Health Risks and Interactions: Tetrodotoxin, found in Taricha newts, can be extremely toxic, with doses as low as 42 micrograms per kilogram of body weight leading to hospitalization or death. Researchers also observed interactions between toxin levels and other sexually dimorphic traits, suggesting potential costs associated with high toxin concentrations. Heavier newts were found to produce higher toxin levels, but the median concentration of toxin remained consistently higher in females, irrespective of size or weight.
This study highlights the intriguing phenomenon of sexual dimorphism in toxin production among Taricha newts. The findings emphasize the significant toxicity of female newts and underscore the importance of handling these amphibians with caution, as they can contain substantial amounts of tetrodotoxin, posing a serious threat to potential predators.
