PhD thesis


7
Short abstract
This thesis deals with selected aspects of brachiopod ontogeny. By use of
immunocytochemistry combined with confocal laserscanning microscopy and
3D reconstruction software the development of the nervous and muscular
system of rhynchonelliform and craniiform brachiopod larvae is described. The
expression patterns of the developmental homeobox containing genes TtrNot
and TtrCdx are described by use of whole mount in situ hybridization. The main
results are: (1) The larval myoanatomy of rhynchonelliform brachiopod larvae is
similar despite gross morphological differences in their outer morphology. (2) The
rhynchonelliform and craniiform brachiopod larvae show a serotonergic nervous
system comprising eight or four flask-shaped cells in the apical organ. An apical
organ comprising flask-shaped cells might be a morphological apomorphy of
Lophotrochozoa. (3) The expression pattern of the TtrNot gene in larvae of
Terebratalia transversa suggests an ancestral role of this gene in gastrulation
and ectoderm specification in Brachiopoda. The expression pattern on TtrCdx
suggests an ancestral role of this gene in gastrulation and the formation of
posterior ectodermal tissue in Brachiopoda.