The origin of muscle from the mesoderm in triploblastic
lineages is a central evolutionary question in higher animals.
Hall, "The neural crest as a fourth germ layer and vertebrates as quadroblastic not triploblastic
," Evolution & Development, vol.
relationships with emphasis on the acoelomates and the position of gnathostomulida, cycliophora, plathelminthes, and chaetognatha: a combined approach of 18s rDNA sequences and morphology.
acredema and Helicoradomenia sp., were examined by transmission electron microscopy and found to be of a triploblastic
metazoan, most probably a polychaete (Todt & Salvini-Plawen 2005).
Despite being trained in comparative anatomy, or perhaps because of it, I was distrustful of some of the morphological criteria - for example, diploblastic versus triploblastic
, or proterostome versus deuterostome - used in reconstructing phylogeny.
differentiation can be widely performed .
Whether the cleavages are spiral or not, a major aspect of the evolution of diploblastic into triploblastic
Metazoa is the formation of a third germ layer, the mesoderm.
They have a primitive morphology with simple triploblastic
bodies (based on body-plan categories).
relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognafha: a combined approach of I8S rDNA sequences and morphology.
Now that many of the components of innate immunity have been identified in cnidarians, we can begin to assess whether they are performing a role homologous to the role in triploblastic