Article Review: Newt Chemical Defenses

Marion ZH , Hay ME (2011) Chemical Defense of the Eastern Newt (Notophthalmus viridescens): Variation in Efficiency against Different Consumers and in Different Habitats. PLoS ONE 6(12): e27581. doi:10.1371/journal.pone.0027581

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0027581

N. viridescens from CofC Herpetology's first field trip.

The eastern newt, Notophthalamus viridescens, has a chemical defense against predators called tetrodotoxin, or TTX. The scientists of this article performed research on the palatability and toxicity of these newts to different predators: largemouth bass, crayfish, bluegill sunfish, and bullfrogs. They offered these animals both a newt and a salamander (Ambystoma). Different species of Ambystoma were chosen as the control because it tends to be in the same habitat, size range, and swimming ability as N. viridescens. A. talpoideum was the control when adult newts were used, and A. maculatum was used with juveniles.

• The largemouth bass and the crayfish had very significant preferences for A. talpoideum; ten A. talpoideum were consumed for every newt consumed. The bass would spit out the newts, and the crayfish eviscerated the newts by trying them and then rejecting them, or just avoiding certain parts of the newt.
• When feeding the bluegill sunfish, the scientists tested to see if certain parts of the newts are more distasteful. The results of these trials found that the viscera were the least rejected, while the dorsal skin was the most rejected. The ventral skin was rejected at a frequency between those two sections.
• The bluegills were also used to test the egg and larval stages. Only three out of ten eggs were accepted, but these fish coughed excessively after doing so; eight out of thirteen larvae were accepted but then spat out and the fish that tried to eat the larvae soon died.
• The bullfrogs ate seven out of eight newts, and did not seem to have any negative health effects from the TTX.

This research is important and interesting because not much research has been done on these newts and TTX. Chemical defenses in animals (whether on the prey or the predator) can lead to the development of various treatments or medications, so I think that it is a good idea to continue research on this. In the case of newts and other amphibians, predators often coexist in a very close range, and this is when chemical defenses are more common methods. All of the predators tested are ones that naturally coexist with the newts.