Sex-Linked Chromosome Heterozygosity in Males of Tityus confluens (Buthidae): A Clue about the Presence of Sex Chromosomes in Scorpions

PLoS One. 2016 Oct 26;11(10):e0164427. doi: 10.1371/journal.pone.0164427. eCollection 2016.

Abstract

Scorpions of the genus Tityus show holokinetic chromosomes, achiasmatic male meiosis and an absence of heteromorphic sex chromosomes, like all Buthidae. In this work, we analysed the meiotic behaviour and chromosome rearrangements of a population of the scorpion Tityus confluens, characterising the cytotypes of males, females and embryos with different cytogenetic techniques. This revealed that all the females were structural homozygotes, while all the males were structural heterozygotes for different chromosome rearrangements. Four different cytotypes were described in males, which differed in chromosome number (2n = 5 and 2n = 6) and meiotic multivalent configurations (chains of four, five and six chromosomes). Based on a detailed mitotic and meiotic analysis, we propose a sequence of chromosome rearrangements that could give rise to each cytotype and in which fusions have played a major role. Based on the comparison of males, females and a brood of embryos, we also propose that the presence of multivalents in males and homologous pairs in females could be associated with the presence of cryptic sex chromosomes, with the male being the heterogametic sex. We propose that the ancestral karyotype of this species could have had homomorphic XY/XX (male/female) sex chromosomes and a fusion could have occurred between the Y chromosome and an autosome.

MeSH terms

  • Animals
  • Chromosome Segregation
  • Embryo, Nonmammalian / metabolism
  • Female
  • Heterozygote
  • In Situ Hybridization, Fluorescence
  • Karyotyping
  • Male
  • Meiosis
  • Mitosis
  • Scorpions / genetics*
  • Scorpions / growth & development
  • Sex Chromosomes*

Grants and funding

This work was supported by grants from the National Council of Scientific and Technological Research (CONICET) (PIP 0342 and PIP 2014-0107) and National Agency for Scientific and Technological Promotion (ANPCyT) (PICT 2010-1665) to LMM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.