MORPHOLOGIC CHANGES IN NOSEMA-ALGERAE (MICROSPORA) DURING EXTRUSION

As a member of the phylum Microspora, Nosema algerae is a small obliga te intracellular parasite. Its free invasive stage is a spore with a c haracteristic cellular organization, including an apically anchored po lar tube that serves as a tool for the transmission of genetic materia l into the host cell. By detailed electron micrographic documentation of the spore ultrastructure we present the aspects related to the biol ogic process of spore extrusion. Our ultrastructure findings confirm t hat the extrusion process of microsporidian spores is based on extreme changes in their organization. This study is the first complete ultra structural documentation of N. algerae concerning the extrusion proces s, which can be subdivided into different stages: the breakdown of the microsporidian cellular compartmentation; the filling of a preformed polar tube with modified sporoplasm; the uncoiling of the polar tube, which in this stage has reached its final length; and, finally, its ex trusion and screw-like movement.