Inhibition of development of anti-predator morphology in the small cladoceran Bosmina by an insecticide: Impact of an anthropogenic chemical on prey-predator interactions

1. The combined effect of the insecticide carbaryl and the predator (Leptodora kindtii) kairomone was assessed on the development of protuberant morphology in the small cladoceran Bosmina fatalis, a feature which evolved originally as a response to the kairomone. The experiment showed that Bosmina changed its morphology in response to the kairomone, but development was inhibited by carbaryl at a sub-lethal concentration even in the presence of the kairomone. At the same time, reduction of fecundity was observed in animals exposed to carbaryl. 2. A short-term feeding experiment (B. fatalis versus Leptodora) indicated that such low concentrations of the insecticide had no impact on predation by Leptodora. Thus, it is suggested that the inhibition of development of anti-predatory defences in Bosmina can increase its vulnerability to predation. 3. Such disturbance of chemical communication by the insecticide reduces the individual survival rate of prey Bosmina in the environment with high predator density. On the other hand, reduction of fecundity may result in decreased population growth rate of animals. 4. The impact of the insecticide on the anti-predator morphology in Bosmina (inhibition) was opposite to that in Daphnia (enhancement). This suggests that biochemical induction processes in the development of anti-predatory morphology are evolutionally different between Daphnia and Bosmina.