Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2790711 | Zoologischer Anzeiger - A Journal of Comparative Zoology | 2012 | 12 Pages |
Abstract
In all of the species studied, the ovaries are made up of germ-line cysts associated with somatic (follicular) cells. The architecture of a germ-line cyst is exactly the same as in other clitellate annelids that have been studied to date. Each germ cell in a cyst has one stable cytoplasmic bridge connecting it with a central anuclear cytoplasmic mass, a cytophore. The fate of germ cells constituting cysts is diverse. The majority of the cells withdraw from meiosis and become nurse cells; only a few continue meiosis, grow and become oocytes. The meroistic mode of oogenesis is suggested. We suggest also that the formation of germ-line cysts and ovary meroism should be regarded as basal conditions for all Clitellata. The occurrence of ovisacs enveloping the ovaries in A. peledina and Hirudinida is regarded as a synapomorphy of both groups, whereas ovaries found in B. pentodonta and B. parasitica have no ovisacs and resemble ovaries described in Oligochaeta sensu stricto.
Keywords
Related Topics
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Agricultural and Biological Sciences
Animal Science and Zoology
Authors
Piotr ÅwiÄ
tek, Anna Z. Urbisz, Witold StrużyÅski, Bartosz J. PÅachno, Aleksander Bielecki, StanisÅaw Cios, Erno Salonen, Jerzy Klag,