Oogenesis of Helobdella ampullariae (Hirudinida, Glossiphoniidae)

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.