[Fasciola haptica L.: the parthenitae in degeneration or without development in Lymnaea truncatula müller (author's transl)].

The authors describe several types of parthenitae in degeneration or without development in infested snails showing the same parasitic phase (phase E 1, characterized by the presence of the first independent cercariae in the visceral cavity of the snail). The influence of three factors, snail-breeding temperature, body volume of the snail host, drying of ground, is analyzed on the quantitative variations of these parthenitae. In nonstarved snails, captive rediae within snail gonad and independent rediae without embryos do not develop. In all cases of snails, the rediae and cercariae can present three types of degeneration: (a) types DE 1 and DE2 (without cellular reaction of the snail) showing nuclear pycnosis (type DE1) or caryolysis (type DE 2); (b) type DE 3 showing nuclear pycnosis with the participation of the snail amebocytes and fibroblastlike cells. In nonstarved snails, the dengeration of rediae - type DE 1 especially - increases noticeably at higher breeding temperatures; on the other hand, the captive rediae are most numerous at low temperatures. In nonstarved snails breeded at the same temperature (20 degrees C), the body volume of the host has more effect upon the location of these rediae in the snail cavity than upon their total number. In starved snails, the degeneration - types DE 1 and DE 2 - first affects all rediae of generations 1 and 2; second, the cercariae degenerate later and the rediae of generation 3 are relatively unaffected by this process. The degenerating rediae in type DE 3 are few in number and only exist in these starved snails. The significance of the degeneration of these parthenitae is discussed.