Fine structure, freeze-fracture and deep-etch views of the sheath and cuticle of microfilariae of Litomosoides chagasfilhoi (Nematoda : Filarioidea)

The fine structure of the sheath and the cuticle of microfilariae of the fi lariid Litomosoides chagasfilhoi is described based on observations made us ing transmission electron microscopy (TEM) and especially on deep-etched re plicas of fully developed intrauterine microfilariae and mature stretched m icrofilariae released by adult females through cultivation in vitro. TEM sh owed that the sheath was trilaminated. In contrast, in deep-etching replica s the sheath presented two layers: an inner layer composed of tightly arran ged globular material, and an outer layer whose external surface was relati vely smooth. Both in thin sections and in classical freeze-fracture and dee p-etched replicas, the cuticle presented two distinct regions: an external one, corresponding to the trilaminated epicuticle, and an inner one, corres ponding to the inner cuticle. Deep-etching replicas revealed that the epicu ticle presented several structures on the annulations of the microfilariae and that the inner region was composed by two parallel rows of globular str uctures.