PhD thesis

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Introduction 11 muscular remodeling during metamorphosis using the following species: Joania cordata (previously Argyrotheca cordata), Argyrotheca cistellula, Novocrania anomala, and Terebratalia transversa. Gene expression Data on the molecular processes that regulate animal development have greatly expanded within recent years (Carroll 2005). The investigation of gene families that encode signaling molecules with roles in the control of cell fate specification, proliferation, movement, and segment polarity has considerably improved our understanding of metazoan ontogeny (Davidson and Levine 2008). So far, only few sequences of developmental genes have been identified in brachiopods, such as members of the Wnt gene family (Holland et al. 1991) and Hox genes (de Rosa et al. 1999), but nothing has so far been published on the expression of these genes during ontogeny. This might not be too surprising, since marine animals as little accessible as brachiopods are unlikely to be favored as candidate model organisms for this kind of studies (Sommer 2009). However, since the bauplan of some brachiopods has not changed significantly since the Early Cambrian, gene expression data from this phylum are very interesting because they may shed light on gene functions in the brachiopod ancestor. This information might contribute to understand the evolution of early bilaterian animals. In this study, the expression patterns of the developmental homeobox genes Not and Cdx were investigated in larvae of the rhynchonelliform brachiopod Terebratalia transversa. This was done in order to reveal the functions of these genes in Brachiopoda and to assess their ancestral function in animal development. Not is a homeobox gene and representatives of its family play an important role during notochord formation in vertebrates (Abdelkhalek et al. 2004). Its role in invertebrate development is not well known (Martinelli and Spring 2004). Cdx is a homeobox gene that is expressed in posterior tissues of almost all phyla investigated so far (Hejnol and Martindale 2008). In addition to the posterior tissues it was found to be expressed in mesoderm, gut, brain, and the central nervous system of mice, lancelets, and annelids, as well as in the gut of Drosophila and the mesoderm of Artemia (Macdonald and Struhl 1986; Duprey et al. 1988; Brooke et al. 1998; Copf et al. 2004; Fröbius and Seaver 2006). The gene expression patterns presented in this <strong>thesis</strong> are the first of their kind for the phylum Brachiopoda.
12 Material and methods Material and methods Immunocytochemistry and phalloidin labeling A range of morphological and molecular methods were applied to representative species of two main groups of Brachiopoda: Rhynchonelliformea and Craniiformea. The musculature was investigated by use of fluorescent conjugated phalloidin. Phalloidin is a toxin found in the mushroom Amanita phalloides and it binds irreversibly to F-actin. The antibodies applied to stain the nervous system bind specifically to neurotransmitters such as serotonin (5-Hydroxytryptamine [5 HT]), neuropeptides such as FMRFamide, or tubulins such as α-tubulin. An overview of the species investigated, the methods, and the antibodies applied is given in Table 1. Labeling of Pax3/7 proteins Arthropods and annelids generate new body segments from a posterior growth zone (Anderson 1973; Meier 1984; Scholtz and Dohle 1996). It has been proposed that the situation in Brachiopoda is comparable to the segmented Annelida (Morse 1871). The larval lobes in rhynchonelliform brachiopods suggest a segmented body plan and a segmented worm like ancestor of Brachiopoda (Morse 1873). In order to investigate if the rhynchonelliform brachiopod larvae of Terebratalia transversa show remnants of segmentation from a potentially segmented ancestor, the larvae were stained with antibodies that bind specifically on proteins of the Pax3/7 gene family. The antibodies DP311 and DP312 detect domains of the Pax 3/7 and non-Pax3/7 proteins in Drosophila and Schistocerca (grasshopper) embryos (Davis et al. 2005). The monoclonal antibodies were raised in mouse and made available by Michalis Averof (Institute of Molecular Biology & Biotechnology, Greece). DP311 stains the following proteins in Drosophila: paired (prd), gooseberry (gsb), gooseberry-neuro (gsbn), aristaless, homeobrain, and repo. DP312 stains prd, gsb, gsbn and Rx. Larvae and juveniles of Terebratalia transversa were collected and fixed as described in Chapter II. The primary antibodies were used in a concentration of 1:30 and the staining was applied as described in Chapters II and III. The stained specimens were analyzed with a Leica DM RXE 6 TL fluorescence microscope equipped with a TCS SP2 AOBS laserscanning device (Leica Microsystems, Wetzlar, Germany).
Page 1 and 2: Comparative neurogenesis, muscle de
Page 3 and 4: 2 Principal supervisor Assoc. P
Page 5 and 6: 4 Preface This thesis presents
Page 7 and 8: 6 Abstract Brachiopods are a sm
Page 9 and 10: 8 Acknowledgements The endeavou
Page 11: 10 Introduction Nervous system Micr
Page 15 and 16: 14 Material and methods purpuratus,
Page 17 and 18: 16 Results and discussion Results a
Page 19 and 20: 18 Results and discussion posterior
Page 21 and 22: 20 Results and discussion Myogenesi
Page 23 and 24: 22 Results and discussion Wanninger
Page 25 and 26: 24 Results and discussion Growth pa
Page 27 and 28: 26 Results and discussion argument
Page 29 and 30: 28 References References Abdelkhale
Page 31 and 32: 30 References priapulids and protos
Page 33 and 34: 32 References James, M. A., Ansell,
Page 35 and 36: 34 References regionalization, prol
Page 37 and 38: 36 References 211. Williams, A., Ca
Page 39 and 40: 38 Chapter II Frontiers in Zoology
Page 53 and 54: 52 Chapter III Chapter III Altenbur
Page 55 and 56: 54 Chapter III Altenburger and Wann
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62 Chapter IV Chapter IV Altenburge
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64 Submitted manuscript Chapter IV
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PhD thesis

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