PhD thesis

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5 Danish abstract Brachiopoda udgør en dyrerække med en unik kropsbygning. Rækken omfatter ca. 370 nulevende arter opdelt i tre undergrupper, Rhynchonelliformea, Craniiformea og Linguliformea, men der er over 12.000 beskrevne fossile arter daterende helt tilbage til tidlig Kambrium. Der er uenighed om brachiopodernes fylogenetiske position som ofte debateres. Mit projekt har belyst dette problem gennem ny indsigt i brachipodernes ontogeni. Jeg har beskrevet udviklingen af nerve- og muskelsystemerne hos de rhynchonelliforme og craniiforme brachiopod larver af henholdsvis Terebratalia transversa og Novocrania anomala ved hjælp af immunohistokemiske indfarvninger kombineret med konfokal laserskanning mikroskopi og 3D-rekonstruktioner. Muskeldannelsen er beskrevet for både larver og voksne af Joania (Argyrotheca) cordata og Argyrotheca cistellula og ekspressionsmønstret af transskriptionsfaktorerne DP311, DP312 (Pax3/7) er beskrevet for larver og voksne af Terebratalia transversa. Ekspressionsmønstret af homeobox-generne TtrNot og TtrCdx er beskrevet for larver og juvenile af Terebratalia transversa ved hjælp af whole mount in situ hybridisering. De væsentligste resultater er: (1) Muskelanatomien hos rhynchonelliforme brachiopodlarver udviser stor lighed trods store forskelle i larvernes ydre morfologi. (2) Rhynchonelliforme og craniiforme brachiopodlarver af henholdsvis Terebratalia transversa og Novocrania anomala udviser et serotoninholdigt nervesystem, som omfatter fire eller otte flaskeformede celler i apikalorganet. Et sådant apikalorgan med flaskeformede celler er muligvis en morfologisk apomorfi for Lophotrochozoa. (3) Ekspressionsmønstret af TtrNot genet hos larverne af Terebratalia transversa indikerer en oprindelig funktion af dette gen i forbindelse med gastrulation, ektoderm specifikation og anlæggelse af nervebaner. For TtrCdx indikerer ekspressionsmønstret en oprindelig funktion i forbindelse med gastrulation samt dannelsen af den bageste del af det ektodermale væv hos Brachiopoda. Resultaterne bliver diskuteret i et fylogenetisk perspektiv gennem sammenligninger med andre rækker indenfor Lophotrochozoa, og implikationerne for evolutionen af Brachiopoda er fremhævet.
6 Abstract Brachiopods are a small phylum with a unique body plan comprising around 370 living species and over 12.000 described fossil species dating back until the Lower Cambrian. The phylogenetic position of brachiopods is under controversial discussion. This project led to new insights into the ontogeny of brachiopods, which are divided into three clades, Rhynchonelliformea, Craniiformea, and Linguliformea. By use of immunocytochemistry combined with confocal laserscanning microscopy and 3D reconstruction software I describe the development of the nervous and muscular system in the rhynchonelliform and craniiform brachiopod larvae of Terebratalia transversa and Novocrania anomala. Myogenesis is described for larvae and adults of Joania (Argyrotheca) cordata and Argyrotheca cistellula and distribution of the transcription factor proteins DP311, DP312 (Pax3/7) for larvae and juveniles of Terebratalia transversa. The expression patterns of the developmental homeobox containing genes TtrNot and TtrCdx in larvae of Terebratalia transversa are described by use of whole mount in situ hybridization. The main results are: (1) The larval myoanatomy of rhynchonelliform brachiopod larvae is very similar, despite gross morphological differences in their outer morphology. (2) The rhynchonelliform and craniiform brachiopod larvae of Terebratalia transversa and Novocrania anomala show a serotonergic nervous system comprising eight or four flask-shaped cells in the apical organ. Such an apical organ with 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. The results are discussed in a phylogenetic framework compared to other lophotrochozoan phyla and implications of the results for the evolution of Brachiopoda are pointed out.
Page 1 and 2: Comparative neurogenesis, muscle de
Page 3 and 4: 2 Principal supervisor Assoc. P
Page 5: 4 Preface This thesis presents
Page 9 and 10: 8 Acknowledgements The endeavou
Page 11 and 12: 10 Introduction Nervous system Micr
Page 13 and 14: 12 Material and methods Material an
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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56 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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