Triploblasten (of lat.-gr. tri ~ ~ blastos and three germ, bud ) are more broadly tissue animals which emerge three germ layers during gastrulation of the blastula. The dreikeimblättrige, so triploblastische embryo is, in the strict sense Triploblast. The three germ layers are the ectoderm, mesoderm and endoderm.
Triploblastie ( Dreikeimblättrigkeit ) is found in all bilaterally symmetrical animals originally and is apparently evolutionarily linked directly with the origin of bilaterality. Zweikeimblättrigkeit ( Diploblastie ) found, however, in the coelenterates, Einkeimblättrigkeit at the fabric-free metazoan Trichoplax adhaerens and the Placozoon.
In view of the presence of a body cavity formed from the mesoderm ( coelomic ) triploblastischen the animals are divided into are not necessarily monophyletic groups of
- Acoelomate: Animals without coelom, only with mesoderm, for example, the flatworms
- Pseudocoelomata: Animals with Pseudocoel, for example, the tube worms
- Coelomata: Animals with true coelom, such as the chordates
Synapomorphies triploblastischer Animals
- Presence of mesoderm
- Bilateral symmetrical plan, in some animals only in the larval stage
- All synapses are monodirectionally
- Presence of a centralized nervous system