Planula

The planula or Planulalarve is a larval form of Cnidarians ( Cnidaria ). It is formed by gastrulation of the blastula, has two layers ( ectoderm and endoderm ) and ciliated. The mouth ( blastopore ) is usually closed directly after the formation again. The planula feeds on plankton ( planktotroph ) or yolk ( lecithotroph ). The flagellum is not uniform everywhere, in the larvae of the anemones ( zoanthids ) is confined to a longitudinal strip. The planula moves in rotation and sets after a planktonic stage of a few days to several weeks with its aboral pole on a firm surface and firmly forms a holdfast. After the metamorphosis to the polyp, with the formation of the mouth occurs, if not already present, and the tentacles. The hydroids ( Hydrozoa ) and the cylinder Rosen ( Ceriantharia ) form the tentacles already during the planktonic phase. The resulting Actinula and Arachnactis larvae are then first free-swimming polyps and go later to life on the ocean floor. In medusenartigen Hydrozoa without alternation of generations, the planula flattens off at their mouth area and the edge of the flattened region is to Medusenglocke.

Source

• Volker Storch, Ulrich Welsch: Systematic Zoology page 54-55, Fischer, 1997, ISBN 3-437-25160-0

• Larva