Copepods are among the most abundant multicellular organisms on earth and they are present in all aquatic ecosystems. They are small crustaceans that can be free living or parasite. For free living copepods they play a key role at the lwoer trophic levels. For planktonic copepods, living in the water column, they are adapted to live in a highly variable and turbulent environment. During several millions of years of evolution, calanoid copepods (see an example of the photo on the right column) developped a typical morphology with large antenna composed of a series of sophisticated mecano- and chemo-receptors. At their small scale (mm to cm), they are very active swimmers with a high jumping capacity. They are a real sophisticated and accurate living biosensors capable of sensing their physical and chemical enviroment. Sami Souissi and his collaborators contributed significantly to promote the use of copepod swimming behaviour to detect the effects of different polutants (i.e., heavy metals, organic pollutants, toxines, nanomaterials and microplastics). 

In freshwater ecosystems the motion of zooplankton, mainly the water flea Daphnia a very known model for toxicity, is used  in a commercial monitoring device called Daphtox. However in both marine and brackish water ecosystems copepods are better candiodates to develop biological models in ecotoxicology (see the book chapter by Kwok et al. 2012 here).

Use of copepod swimming behaviour to assess the water quality.