Do potential predators induce an avoidance response in Daphnia carinata?

Chemicals exuded by predators (kairomones) are known to induce the daytime descent of several species of Northern Hemisphere Daphnia. The vertical mig ration of New Zealand's native Daphnia carinata King has not been studied, however, and its response to kairomones is not known. We compared the behav ioural responses of D. carinata to water from around two predatory fish, co mmon bully (Gobiomorphus cotidianus) and inanga (Galaxias maculatus), an aq uatic insect (Anisops wakefieldi), and several concentrations of trimethyla mine (TMA), a fish-mediated chemical. The responses of Daphnia were assesse d in nine trials by comparing their vertical distribution in cylinders of w ater before and after exposure to water that had contained each predator, o r TMA. D. carinata did not alter their vertical distribution in response to water from around Anisops. However, they descended when exposed to water f rom around inanga in 83% of trials and common bully in 67% of trials. They also descended in response to TMA in the range, 1 12.5-500 muM. Analysis of these "fish waters" failed to detect TMA at greater than or equal to 20 mu M, so that we cannot conclude that the behavioural cue from these fish is T MA.