LAUSR

The knowledge of gametogenesis in crustaceans allows to differentiate the stages of development during the reproductive cycle and to interpret aspects of its population dynamics. A microanatomical study of the ovary and oogenesis of the freshwater amphipod Hyalella curvispina was performed. The crustaceans were collected in Arroyo Rivera (Saldungaray, Buenos Aires Province, Argentina). Ovarian cell types were described and germ cells (oogonies, oocytes in previtelogenesis, incipient and advanced vitellogenesis) and their modifications throughout oogenesis were characterized microscopically. The ovary is characterized by an intraovarian zonation because the germinal elements develop in superimposed longitudinal bands. Oogenesis comprises four stages: meiosis, previtellogenesis, primary and secondary vitellogenesis. During vitellogenesis, the oocyte I increases its nuclear and cytoplasmic size as a product of the synthesis and accumulation of the reserves. The yolk resulting from primary vitellogenesis is endogenous. The marked increase in oocyte sizes is concomitant with the appearance of follicular cells, which play a preponderant role during secondary (exogenous) vitellogenesis. Keywords: histology, gonad, Amphipoda, freshwater.