title: [Haplodiploidy of Oxyurida. Effects of this phenomenon in the life cycle].
abstract: Chromosome behavior during gametogenesis and early cleavage is studied in two species of Thelastomatidae (Oxyurida), Hammerschmidtiella sp. and Thelastoma sp., parasites of diplopods. Both species are shown to be haplodiploid: male with 4 Thelastoma) or 5 (Hammerschmidtiella) chromosomes and double this number in the corresponding female. Haplodiploidy is now known in the 4 families of the Oxyurida and the author concludes that this form of reproduction is characteristic of the entire order. The Oxyuridan life cycle seems simple: 2 moults in the egg, no intermediate host, no extra-intestinal migration. However, several findings (some quite recent) indicate that this life cycle is often complicated by phenomena very closely adapted to host biology. The following particularities are analysed: 1) male progenesis; 2) laying of eggs in agglomerated packets; 3) peri-anal egg deposition; 4) poecilogony; 5) spanandry; 6) traumatic extra-genital insemination; 7) thelytoky. In a final chapter the author relates these adaptations to host biology and attempts to explain how they may have come to be favoured by natural selection during the course of evolution.
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000502:physiology*; D004171:Diploidy; D005260:Female; D006238:Haploidy; D008297:Male; D010124:Oxyuroidea / Q000235:genetics* / Q000254:growth & development
vernacular_title: L'haplodiploidie des oxyurida. Incidence de ce phénomène dans le cycle évolutif.