Dokumentation des Metamorphoseablaufs bei Actinotrocha branchiata (Phoronidea)

Abstract

During metamorphosis, the larvae of Phoronis muelleri (named Actinotrocha branchiata) produce a slimy cover, to which little stones adhere and prevent direct observations. For the first time, it has been possible to obtain the metamorphosis of Actinotrocha branchiata without adhering bottom material. The course of the metamorphosis, which begins with the evagination of the metasome diverticles and takes about 11-15 minutes, can be divided into six phases: (a)Actinotrocha branchiata ready to metamorphose; (b) phase immediately prior to metamorphosis; (c) evagination of metasome diverticles; (d) dislocation of the gut; (e) transformations in the area of the episphaere-tentacles; (f) terminal phase of metamorphosis, which leads to the sessile Phoronis muelleri. All stages are described and photographically documented. © 1973 Biologischen Anstalt Helgoland.