title: Parastrongyloides trichosuri suggests that XX/XO sex determination is ancestral in Strongyloididae (Nematoda).
abstract: The parasitic roundworms Strongyloides stercoralis (in man) and Strongyloides ratti (in rats) employ environmentally controlled XX/XO sex determination with a pair of X chromosomes and two pairs of autosomes. Strongyloides papillosus (in sheep) has only two pairs of chromosomes, one of which combines the genetic material homologous to the S. ratti chromosomes X and I. This species creates males through the elimination of one copy of the portion related to the X chromosome (chromatin diminution). It is not clear which one of these two sex-determining mechanisms is ancestral. We demonstrate that Strongyloides vituli (in cattle) has two pairs of chromosomes like its very close relative S. papillosus whereas Parastrongyloides trichosuri, a closely related out-group to Strongyloides spp. in Australian brushtail possums, has three chromosome pairs and employs XX/XO sex determination. The X chromosome of P. trichosuri is homologous to the X chromosome of S. ratti. Our data strongly suggest that the last common ancestor of Strongyloides spp. and Parastrongyloides spp. had two pairs of autosomes along with two or one X chromosome in females and males, respectively. The situation with two pairs of chromosomes is likely derived and occurred through the fusion of the X chromosome with an autosome.
authors: Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, D-72076 Tübingen, Germany.
authors: Arpita
authors: A
authors: Kulkarni
authors: Anna
authors: A
authors: Dyka
authors: Linda
authors: L
authors: Nemetschke
authors: Warwick N
authors: WN
authors: Grant
authors: Adrian
authors: A
authors: Streit
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D059785:Karyotype; D008297:Male; D017168:Rhabditida / Q000235:genetics*; D019849:Sex Determination Processes / Q000235:genetics*; D014960:X Chromosome