Invasive species are a significant threat to freshwater ecosystems. In 2000, New Zealand Mud Snails, (Potamopyrgus antipodarum) were detected in streams throughout the Santa Monica Mountains (Los Angeles, CA, USA). Many of these streams are inhabited by the California newt (Taricha torosa), which produces tetrodotoxin (TTX), a neurotoxin utilized for self-defense. However, this toxin has been shown in previous studies to affect the behavior of freshwater invertebrates. We used laboratory studies to assess the effect of California newt toxins on New Zealand Mud Snail behavior. The first study examined if newt chemical cues would affect the movement of New Zealand Mud Snails. Snails were placed in chambers containing water with newt cues, water with bullfrog cues, or control water. The distance moved by each snail in the six ten minute intervals were measured and recorded. These experiments were then repeated using TTX in place of newt chemical cues to determine the effect of the toxin only.
Our analyses showed that mean snail movement significantly differed between all treatments. In water containing 3 x 10-8 mol/L of pure TTX we found that snail movement decreased to 0 over a one-hour period. After confirming the effect of pure TTX on New Zealand Mid Snail movement we examined New Zealand Mud Snails exposed to newt cues in water and found they moved significantly less relative to controls. Mean movement in a ten-minute interval decreased by 44% in water containing newt chemical cues. Future studies will assess the response of New Zealand Mud Snails under field conditions in the presence and absence of California newts. These data suggest that California newts could play an important role in limiting the spread of invasive mud snails in Santa Monica Mountain streams.