Phoronis muelleri (Phoronida), actinotrocha larva, Helgoland 08.2011. 0:37 min. The phoronids larvae 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. Video can be used for teaching.