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dc.contributor.supervisorHuebner, Erwin (Biological Sciences)en
dc.contributor.authorBrubacher, John Lewis
dc.date.accessioned2010-09-10T21:29:32Z
dc.date.available2010-09-10T21:29:32Z
dc.date.issued2010-09-10T21:29:32Z
dc.identifier.citationBrubacher, John L. and Huebner, Erwin (2009). Development of polarized female germline cysts in the polychaete, Ophryotrocha labronica, Journal of Morphology 270(4):413-429en
dc.identifier.urihttp://hdl.handle.net/1993/4144
dc.description.abstractIn 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.extent62133731 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoengen_US
dc.rightsinfo:eu-repo/semantics/openAccess
dc.subjectoogenesisen
dc.subjectnurse cellsen
dc.subjectoocytesen
dc.subjectAnnelidaen
dc.subjectpolychaetesen
dc.subjectgerm cellsen
dc.titleOogenesis in the polychaete worm, Ophryotrocha labronicaen
dc.typeinfo:eu-repo/semantics/doctoralThesis
dc.typedoctoral thesisen_US
dc.degree.disciplineBiological Sciencesen_US
dc.contributor.examiningcommitteeMarcus, Jeffrey (Biological Sciences) Merz, David (Biochemistry and Medical Genetics) Eckelbarger, Kevin (School of Marine Sciences, University of Maine)en
dc.degree.levelDoctor of Philosophy (Ph.D.)en_US
dc.description.noteOctober 2010en


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