Apomictic Reproduction in the Amazon Molly, Poecilia formosa, and Its Triploid Hybrids

  • Paul J. Monaco
  • Ellen M. Rasch
  • Joseph S. Balsano
Part of the Monographs in Evolutionary Biology book series (MEBI)


The Amazon molly, Poecilia formosa, initially described in 1859 by Girard, is the first vertebrate in which unisexuality was recognized (Hubbs and Hubbs, 1932). Poecilia formosa is intermediate in form between two sexual species, Poecilia latipinna (LeSueur) and Poecilia mexicana Steindachner and is thought to have arisen in nature as a hybrid of these species (Hubbs and Hubbs, 1932; Hubbs, 1955, 1964; Abramoff et al., 1968; Prehn and Rasch, 1969; Balsano et al., 1972). Poecilia formosa is not a true thelytokous parthenogen as defined by White (1973); instead, it reproduces by gynogenesis, a mechanism that is sperm dependent. Males of related sexual species provide sperm, which serve only to activate the egg. Functional syngamy does not occur. Thus, developing embryos are derived from diploid ova that contain only maternal chromosomes and each daughter is a genetic copy of its mother (Meyer, 1938; Hubbs and Hubbs, 1946; Kallman, 1962a,b,c; Hubbs, 1964; Rasch et al., 1965; Darnell et al.,1967; Schultz, 1969; Uzzell, 1970; White, 1973). The obligatory dependence on sperm that is a hallmark of gynogenetic reproduction compels P. Formosa to behave in nature as a sexual parasite on closely related, sympatric bisexual species (Hubbs, 1964). Although a variety of poeciliid males can “father” P. formosa in the laboratory (Hubbs and Hubbs, 1946), the survival and success in nature of these all-female forms require their coincident distribution with at least one of the bisexual host species.


Synaptonemal Complex Meiotic Prophase Triploid Hybrid Primary Oocyte Maturation Division 
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Copyright information

© Plenum Press, New York 1984

Authors and Affiliations

  • Paul J. Monaco
    • 1
  • Ellen M. Rasch
    • 1
  • Joseph S. Balsano
    • 2
  1. 1.Department of Biophysics, Quillen-Dishner College of MedicineEast Tennessee State UniversityJohnson CityUSA
  2. 2.Biomedical Research InstituteUniversity of Wisconsin-ParksideKenoshaUSA

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