[On the organogenesis of Seuratum cadarachense Desportes, 1947 (Nematoda Seuratoidea) and the cellular reactions of the intermediate insect host Locusta migratoria (author's transl)].

The adaptation of primitive heteroxenous nematodes, parasites of vertebrates, to the intermediate host, is detailed by studying the organogenesis of the first larval stages of the Seuratoid nematode Seuratum cadarachense and an histological approach of the cellular reactions caused by the penetration and the development of the parasite in the insect Locusta migratoria. The larval organization of Seuratum at hatching is similar to that of Subuluridae and characterized by a large number of initial cells: among them, eight cells alined in a row forming the intestinal primordia, and two mesenchymal cells. In Seuratum, as in Subulurid in general, the first larval stage has a slow development. The larval migration occurs in the wall of the mesenteron. Hemocytic capsules are observed in the hemocoel in contact with the muscle fibers of the mesenteron. Some of them show necrotic features which bear witness to an imperfect adaptation of the nematode to the intermediate host.