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On the evolution of cnidarian eyes

Stierwald, Michael. On the evolution of cnidarian eyes. 2004, Doctoral Thesis, University of Basel, Faculty of Science.

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Official URL: http://edoc.unibas.ch/diss/DissB_6788

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Abstract

Cnidarians and their medusa stage are generally considered to be diploblasts and therefore ancestral to Bilaterians. They represent the most primitive phylum where striated muscle tissue, a complex system of nerve rings and different sense organs of high complexity, including eyes have evolved in the jellyfish stage. We demonstrated that jellyfish and the triploblast Bilateria use homologous gene cascades and developmental pathways to build these muscle systems. The expression of JellyD, a derived jellyfish homolog of the master regulator of muscle tissue MyoD, is correlated with that of bilaterian muscle determination factors. Furthermore, the eye determination genes of the Pax and Six families of cnidarians have bilaterian-like expression patterns. Although no bona fide Pax6 homolog could be found, it can be shown that among the four Pax genes characterized, cnidarians do have a Pax gene (PaxA-Cr) that is exclusively expressed in the maintenance and regeneration of eye tissue. Additionally the hypothesis of a loss of Pax genes within the cnidarians can be rebut as well as the claim that cubozoans would possess only one Pax gene. Cladonema jellyfish have three cognate members of the sine oculis/Six class family of which Six1/2-Cr and Six3/6-Cr are upregulated during eye regeneration. Analysis of gene expression patterns during eye regeneration shows that the cnidarian Pax gene is upregulated before the Six genes, indicating a possible upstream position in the gene regulatory network. The results are in agreement with monophyly of eye evolution and indicate that the common ancestor between Cnidaria and Bilateria had a more complex anatomy than commonly anticipated.
Advisors:Schmid, Volker
Committee Members:Reichert, Heinrich and Gehring, Walter Jakob
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Zoologie
UniBasel Contributors:Reichert, Heinrich and Gehring, Walter Jakob
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:6788
Thesis status:Complete
Bibsysno:Link to catalogue
Number of Pages:186
Language:English
Identification Number:
Last Modified:22 Jan 2018 15:50
Deposited On:13 Feb 2009 14:50

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