Alarm substances are chemicals used by aquatic organisms, including fish and tadpoles, as indicators of the presence of predators. Alarm substances trigger morphological and behavioral responses to predation on conspecifics. We exposed tadpoles of the Wood Frog (Rana sylvatica) to various waterborne cues to find the source of chemical alarm substances in tadpoles. Tadpoles were much less active in water in which dragonfly larvae had fed on either live or anesthetized tadpoles than in control water or water in which we simulated attacks on tadpoles with a hypodermic needle. This result shows that tadpoles do not have to be conscious in order for the alarm substance to be released and further suggests that the release of the alarm substance occurs when the dragonfly larvae actually feeds on tadpoles.
Ethan Schniedermeyer, ’01 St. Louis, MO
Sponsor: S. Andrew McCollum