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dc.contributor.supervisor Huebner, Erwin (Biological Sciences) en
dc.contributor.author Brubacher, John Lewis
dc.date.accessioned 2010-09-10T21:29:32Z
dc.date.available 2010-09-10T21:29:32Z
dc.date.issued 2010-09-10T21:29:32Z
dc.identifier.citation Brubacher, John L. and Huebner, Erwin (2009). Development of polarized female germline cysts in the polychaete, Ophryotrocha labronica, Journal of Morphology 270(4):413-429 en
dc.identifier.uri http://hdl.handle.net/1993/4144
dc.description.abstract In most animals, oogenesis involves a syncytial “cyst” stage. Cysts are produced by incomplete mitotic divisions of gonial precursor cells, leaving the resulting cystocytes interconnected by cytoplasmic bridges. The bridges subsequently break down, liberating the developing gametes. In some animals (e.g. meroistic insects) cysts are “polarized”, such that certain cystocytes differentiate as supportive nurse cells, rather than oocytes. The variability of cysts in animal oogenesis contrasts with the relative universality of spermatogenic cysts, making the functional importance of cysts in oogenesis unclear. I have studied oogenesis in a polychaete worm, Ophryotrocha labronica (Annelida: Dorvilleidae). These worms produce polarized, two-celled oogenic cysts with one nurse cell and one oocyte. Such cysts resemble their better-characterized counterparts in meroistic insects. However, using a variety of light- and electron-microscopic techniques, I show here that the resemblance between O. labronica and meroistic insects is largely superficial. Rather, the roles of nurse cells and the mechanisms underlying cystocyte differentiation are quite distinct in both groups. Therefore, similarities between these polychaetes and insects are probably examples of convergent evolution rather than homology. These observations underscore the plasticity of oogenesis among animals. Mechanisms by which germ cells become distinct from somatic cells in animals are also a subject of considerable research activity. Two general modes of germ-cell specification have been described in animals: deterministic specification, which is typical of established model species (e.g., Drosophila melanogaster and Caenorhabditis elegans) and inductive specification, which, though it is the more-common mode among animals, has not been well studied. As an annelid worm, O. labronica likely specifies its germ cells inductively, and therefore has potential to serve as a model species for studies of inductive germ cell specification. Realizing this potential, however, will require the development of genetic resources for this species. I describe the beginnings of such work here: the isolation and characterization of a vasa/PL10-like gene whose expression is largely restricted to germ cells, the construction of a cDNA library, and the refinement of methods for in situ hybridization and immunostaining to visualize gene expression in whole worms. en
dc.format.extent 62133731 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject oogenesis en
dc.subject nurse cells en
dc.subject oocytes en
dc.subject Annelida en
dc.subject polychaetes en
dc.subject germ cells en
dc.title Oogenesis in the polychaete worm, Ophryotrocha labronica en
dc.degree.discipline Biological Sciences en
dc.contributor.examiningcommittee Marcus, Jeffrey (Biological Sciences) Merz, David (Biochemistry and Medical Genetics) Eckelbarger, Kevin (School of Marine Sciences, University of Maine) en
dc.degree.level Doctor of Philosophy (Ph.D.) en
dc.description.note October 2010 en


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