title: Sex ratios provide evidence for monozygotic twinning in the ring-tailed lemur, Lemur catta.
abstract: Monozygotic (MZ) twinning is generally considered to be rare in species other than human. We inspected sex ratios in European zoo-bred ring-tailed lemurs (Lemur catta), revealing a significant excess of same-sex twins. Of 94 pairs, 60 (64%) were either both males or both females (p = .004). Application of the Weinberg differential rule argues that 27% of all twins in this species are MZ pairs. In this protected species, where twinning is commonplace (~50% of newborns are twins), the probable existence of frequent MZ twinning has ramifications for breeding programs aimed to maximize genetic diversity, and suggests that twin studies in a species other than human could have potential as a medical research tool.
authors.affiliation: Pieta Research, Edinburgh, UK.
authors.forename: John
authors.initials: J
authors.lastname: St Clair
authors.affiliation: Animals, Conservation Programmes, and Education Department, Royal Zoological Society of Scotland, Edinburgh, UK.
authors.forename: Roisin
authors.initials: R
authors.lastname: Campbell-Palmer
authors.affiliation: Pieta Research, Edinburgh, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Lathe
mesh_terms: D000818:Animals; D005260:Female; D006801:Humans; D007900:Lemur / Q000235:genetics* / Q000502:physiology; D008297:Male; D011247:Pregnancy; D012744:Sex Ratio; D038522:Twinning, Monozygotic / Q000235:genetics*