From Small to Large Scale: A Review of the Swimming Behaviour of Daphnia

Daphnia species are key components of pelagic freshwater ecosystems for their trophodynamic position, being the most important phytoplankton grazer while at the same time representing the main food resource for several fish species. Their ecological role is mediated by their behaviour, both at the scale of the individual organisms and over the extension of the water column. In this contribution we will review the swimming behaviour of Daphnia species. We will first focus on the motion patterns displayed by individual daphnids at small scales, paying attention to the mechanisms by which these small crustaceans adapt plastically to the different environmental conditions they face. Subsequently, we will move to larger scales, highlighting how the behaviour at the individual scale can have strong repercussions on the dynamics observed at the scale of the population. This will give a wide-ranging contextualisation of the links between processes acting over different spatial and temporal scales.