Phoronis muelleri (Phoronida), actinotrocha larva, Helgoland 06.2017. 1:16 min. Actinotrocha larvae may be numerous in summer plankton, living there for some weeks. They start with tiny forms about 50 µm in length which soon develops first tentacles becoming more numerous up to 48 in some species. Old larvae reach a length up to 1 mm. The mouth is hidden under a pre-oral lobe. Cilia on the tentacles and a heavily ciliated telotroch around the anus propel the larvae through the water. Different video-clips show different stages of development. Video can be used for teaching.