Anthropogenic chemicals (insecticides) disturb natural organic chemical communication in the plankton community

The present paper reviews the results of several experiments dealing with the effects of insecticides on natural organic chemical communication in the plankton community. Some species of the cladoceran Daphnia develop protuberant structures (neckteeth, high helmets, long tailspines), an anti-predator strategy, when exposed to a chemical (kairomone) released from predators, such as larvae of the midge Chaoborus. The same morphological changes in Daphnia are induced by exposure to high concentrations of carbamate and organophosphorus insecticides, when animals are in the final embryo to the first instar stage. Lower (sublethal) concentrations of insecticides also can affect morphology of the Daphnia, if the animals are exposed to both insecticides and the Chaoborus kairomone simultaneously. The Chaoborus kairomone reduces clutch size and increases maturation time of Daphnia and thus reduces Daphniaʹs population growth rate. Low concentrations of insecticide cause a more marked reduction in the population growth rate when Daphnia were exposed simultaneously to the Chaoborus kairomone, and synergism in the effects of the two kinds of chemicals has been detected. Because kairomones are a messenger in the chemical communication between planktonic predators and preys, it could be said that anthropogenic chemicals (insecticides) disturb natural organic chemical communication in the plankton community. This is similar to the effect of environmental endocrine disrupters (EEDs) which are anthropogenic chemicals that disturb chemical communication between tissues or organs in the bodies of animals.