Acartia tonsa (Crustacea, Copepoda, Calanoida, Acartiidae), body length 900 µm, Helgoland 08.2020. 1:30 min. Acartia tonsa is a species living in brackish lagoons and estuaries. It can be cultured easily. These specimens come from a culture of the Biologische Anstalt Helgoland. They can be found in brackish waters of estuaries and lagoons, e. g. in the Mediterranean. Antennae 1 of the genus with characteristic pattern of setae. Urosome as in many copepods with a fan of plumose setae. Suspension feeders, maxilla 2 forms a feeding basket. Video can be used for teaching.