To flee or not to flee: detection, avoidance of and attraction to food resources by Daphnia magna studied with an olfactometer

The cladoceran herbivore Daphnia magna is a major consumer of phytoplankton in lakes. Therefore, this organism may control the phytoplankton community and the proliferation of some algae or cyanobacteria. Cladoceran behaviour and migration in relation to temperature, light or presence of planktivorous fishes have been well studied. In particular, it is known that the detection of kairomones produced by predators may induce avoidance. Avoidance could also occur with other semiochemicals such as cyanotoxins. In order to explore this hypothesis, authors used an olfactometer to observe and measure the exploratory behaviour of D. magna individuals based on the motivation for food. Daphnids were allowed to choose between different compounds. With this experimental design, authors observed that 1) cladocerans are able to detect resources with different qualities, 2) they can explore before exhibiting preferences, and 3) daphnids are able to avoid compounds that are potentially toxic. The study of zooplankton ability to explore the environment when exposed to semiochemicals needs further investigation.