2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

�22 Franziska Anni Franke A 704 / 16:45
Study of segment polarity genes in Onychophora (velvet worms): Insights into the
evolution of segmentation in Panarthropoda
Authors: Franziska Anni Franke 1 , Georg Mayer 1
Affiliation: 1 Animal Evolution & Development, Institute of Biology, University of
Leipzig
Organisation of the body into serially repeated units or segments is found in several
distantly related animal groups, including chordates, annelids and arthropods. The
evolutionary origin of body segmentation in these groups is under debate and it is
unclear whether segmentation has evolved once, twice, or several times among
bilaterians. Gene expression studies in one of the closest relatives of arthropods, the
Onychophora, might help to clarify this issue since the onychophoran body shows
both segmental and non-segmental features. To assess whether onychophorans and
arthropods share a common segment patterning mechanism, we analysed the
expression pattern of the segment polarity genes engrailed, hedgehog, wingless and
cubitus interruptus, which play a major role in the segmentation process of the
arthropod embryo. Our data show that despite differences there are also similarities
in the segmentation process of the onychophoran embryo to that in arthropods,
suggesting that the subdivision of the body into repeated, antero-posterior genetic
units predated the evolution of externally visible segmental boundaries in the
panarthropod lineage.
�23 Reinhard Schröder A 704 / 17:00
FGF signalling organizes extraembryonic membrane formation and integrity in the
red flour beetle Tribolium castaneum
Authors: Reinhard Schröder 1 , Rahul Sharma 1 , Anke Beermann 2
Affiliations: 1 Universität Rostock; 2 Universität Tübingen
Fibroblast growth factor (FGF) signalling plays a key role in cell proliferation and differentiation
in both vertebrates and invertebrates. To gain insight into FGF signalling
in an arthropod, we functionally characterized the Fgf1 ortholog in the beetle
Tribolium that is not represented in the Drosophila genome. Tc-fgf1 RNA-interference
results in asynchronous nuclear division seen already during blastoderm formation.
Tissue-specific marker genes analysis reveals a loss / severe reduction of extraembryonic
membranes in the affected embryos. As a consequence, secondary
phenotypes develop later during embryogenesis such as (I) mispositioning of the
germ anlage resulting in a novel “floating embryo” phenotype, (II) completion of
embryogenesis around the posterior pole resulting in a curved embryonic axis and
(III) impairment of dorsal closure. We discuss whether these phenotypes might be
caused in part by changes of the expression level of Tc-dpp in Tc-fgf1-RNAi embryos.
This is the first study reporting the functional characterization of Fgf1 outside the
vertebrate system.
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