Testisacs microanatomy and spermatogenesis of Helobdella simplex (Hirudinida: Glossiphoniidae)

Abstract

The aim of this study was to describe the testisac microanatomy and spermatogenesis of Helobdella simplex (Moore, 1911). The leeches were collected in the Sauce Chico River (Tornquist) during April 2012. The collection of material was carried out manually by checking rocks, logs, leaves and artificial substrates in the river bed. Helobdella simplex has six pairs of testisacs located between the gastric caeca. The testisac wall has two structurally and functionally differentiated cell types: the lining mesothelial cells and the germline cells. The lining cells are flat and form a continuous layer. In H. simplex no ciliated cells were observed into the testisacs, nor the formation of spermatogonia due to detachment of the testicular wall. Cell types were microscopically characterized, and five spermatogenesis stages are described, taking into account the maturation of germinal cells, the morphological changes in the cytophore and phagocytic activity. Testicular phagocytes actively participate during spermatogenesis. They are involved both in the removal of defective cells during the early stages of spermatogenesis and in the removal of the cytophore during the reacting reabsorption. Our study adds the knowledge of spermatogenesis in H. simplex and might be useful to differentiate the stages of development during the reproductive cycle, and to interpret aspects of its population dynamics.