title: Co-segregation of sex chromosomes in the male black widow spider Latrodectus mactans (Araneae, Theridiidae).
abstract: During meiosis I, homologous chromosomes join together to form bivalents. Through trial and error, bivalents achieve stable bipolar orientations (attachments) on the spindle that eventually allow the segregation of homologous chromosomes to opposite poles. Bipolar orientations are stable through tension generated by poleward forces to opposite poles. Unipolar orientations lack tension and are stereotypically not stable. The behavior of sex chromosomes during meiosis I in the male black widow spider Latrodectus mactans (Araneae, Theridiidae) challenges the principles governing such a scenario. We found that male L. mactans has two distinct X chromosomes, X1and X2. The X chromosomes join together to form a connection that is present in prometaphase I but is lost during metaphase I, before the autosomes disjoin at anaphase I. We found that both X chromosomes form stable unipolar orientations to the same pole that assure their co-segregation at anaphase I. Using micromanipulation, immunofluorescence microscopy, and electron microscopy, we studied this unusual chromosome behavior to explain how it may fit the current dogma of chromosome distribution during cell division.
authors.affiliation: New York State Department of Health, Wadsworth Center, Albany, NY, 12201-0509, USA.
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Ault
authors.affiliation: Biology Department, Bucknell University, Lewisburg, PA, 17837, USA.
authors.forename: Kristen D
authors.initials: KD
authors.lastname: Felt
authors.affiliation: Biology Department, Bucknell University, Lewisburg, PA, 17837, USA.
authors.forename: Ryan N
authors.initials: RN
authors.lastname: Doan
authors.affiliation: Biology Department, Bucknell University, Lewisburg, PA, 17837, USA.
authors.forename: Alexander O
authors.initials: AO
authors.lastname: Nedo
authors.affiliation: Biology Department, Bucknell University, Lewisburg, PA, 17837, USA.
authors.forename: Cassondra A
authors.initials: CA
authors.lastname: Ellison
authors.affiliation: Biology Department, Bucknell University, Lewisburg, PA, 17837, USA. le.paliulis@bucknell.edu.
authors.forename: Leocadia V
authors.initials: LV
authors.lastname: Paliulis
mesh_terms: D000818:Animals; D001740:Black Widow Spider / Q000235:genetics*; D020090:Chromosome Segregation; D008297:Male; D008540:Meiosis; D012730:Sex Chromosomes / Q000235:genetics*
keywords: Latrodectus mactans; Meiosis; Orientation stability; Sex chromosomes; Spiders