Abstract
The knowledge of the gametogenesis in Hirudinida is an important tool that allows the understanding of the reproductive cycle. Ovogenesis of Helobdella ampullariae was described based on 30 leeches collected from mantle cavity and lung of Pomacea canaliculata . By means of histological analysis, seven stages were recognized during the oogenesis process, which were defined considering nuclear transitions of germ cells, cytoplasmic-nucleus diameter variations, presence and evolution of reserves. It was determined that oogenesis is a synchronous process, since all oocytes are in the same stage of development. During the phases of proliferation and meiosis, the ovarian cord increases its volume and the oocytes undergo the prophase of the first meiotic division. During the stages of previtelogenesis and vitellogenesis, the oocyte I increases its size within the framework of the vitellogenesis process. The first phase of oocyte growth is related to the incorporation of cellular components of the nurse cells (incipient vitellogenesis) and the second with the formation of yolk plates (advanced vitellogenesis). The post-laying period is characterized by the retraction of ovisaco walls, and by the reabsorption processes that affect the ovarian cord. The microanatomic examination allowed to confirm that sexual maturity occurs inside the host mollusk. Keywords: histology, ovary, leeches.
Highlights
Son simbiontes facultativos y se asocian de manera temporal u oportunista con sus hospedadores (Damborenea et al, 2017)
Los celomocitos se aplanan distendiéndose por el crecimiento de los ovocitos (Figuras 2A-B)
Durante esta etapa se constató la presencia de espermatozoides en el tejido conectivo como resultado de impregnación hipodérmica (Figuras 2C-D)
Summary
Para estudiar la ovogénesis de Helobdella ampullariae se emplearon 30 hirudíneos en diferentes estadios de madurez sexual hallados en la cavidad paleal y pulmón de 19 ejemplares de Pomacea canaliculata que fueran recolectados en un canal artificial próximo a la desembocadura del Río de la Plata en el Balneario Bagliardi (Provincia de Buenos Aires, Argentina). Cada ovario está rodeado por un saco celómico especializado (ovisaco) conformado por un epitelio externo y uno interno. El ovisaco rodea una cavidad llena de fluido hemocelómico donde se halla contenido el cordón ovárico, conformado por células germinales y células nodrizas rodeadas de una capa de células foliculares. Cada célula nodriza está unida a una masa central denominada citóforo o raquis el cual conecta los ovocitos en crecimiento. En H. ampullariae se reconocieron siete etapas durante el proceso de ovogénesis: I y II (proliferación y meiosis), III a VI (previtelogénesis y vitelogénesis) y VII (post-puesta)
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