[Ormiersia carcini gen. n., sp. n., microsporidian of the Mediterranean crab, Carcinus mediterraneus Czerniavsky, 1844: developmental cycle and ultrastructural study].

A microsporidan parasite, Ormieresia carcini gen. n., sp. n., was found in the crab, Carcinus mediterraneus Czerniavsky. Its development and fine structure are the subject are the subject of the present study. The life cycle begins with a schizont surrounded by a unit membrane and containing a diplokaryon. The entire process of sporogony takes place in the host musculature. The sporogonic stages are enclosed in the pansporoblastic membrane. In each pansporoblast, sporogony gives rise to 8 sporoblasts; the octonucleate sporogonial plasmodium is lacking. In the course of schizogonic and sporogonic divisions, each kinetic center consists of 2 plaques, one located within and the other outside the nuclear envelope. The dividing sporonts and sporoblasts sevrets "metabolic" substances (granules, tubules) which are depostied in the pansporoblast. The uninucleate spore is long and cylindrical, measuring 19.1 X 2.4 micronm. A rectilinear manubrium traverses the spore. Its posterior end attenuates abruptly into a polar filament with 4 or 5 coils; its anterior end is attached to the polar cap, which is compressed by a double polar ring. The anterior part of the manubrium is surrounded by a polaroplast consisting of a "spongy" (vesicular) and a lamellar zone.