On the development of the alternating free-living and parasitic generations of the nematodeRhabdias bufonis

Abstract

Summary The nematode Rhabdias bufonis is an anuran lung parasite with a heterogonic life cycle, characterized by alternation of gonochoristic (free-living) and hermaphroditic (parasitic at late larval and adult stages) generations. Adult parasites containing unhatched embryos were isolated from infected amphibians, but all other stages were cultured under controlled laboratory conditions with bacteria on agar plates. Development was studied with particular reference to a comparison of the two generations. No deviation from the strict heterogonic life cycle could be induced by alterations in the conditions of culture. The early embryonic lineages in the two generations are similar but not identical. Early development in both generations takes approximately twice as long as that in Caenorhabditis elegans, and the sequence of divisions is more variable. Nuclei counted in late embryos were similar in number (mean numbers: free-living generation 502; parasitic generation 570). Their number increases only moder...