Theoretical and Applied Genetics

, Volume 82, Issue 2, pp 153–160

Sex determination in the genus Oreochromis

2. Sex reversal, hybridisation, gynogenesis and triploidy in O. aureus Steindachner
  • G. C. Mair
  • A. G. Scott
  • D. J. Penman
  • D. O. F. Skibinski
  • J. A. Beardmore
Originals

Summary

Sex ratios from 62 single-pair matings of normal broodstock O. aureus were highly heterogeneous with an overall deficit of males (41.4%). Peaks in the sex ratio frequency distribution occurred at 1∶1, 3∶5 and 1∶3 (male∶female). Hybridisation of O. aureus with O. mossambicus, O. spilums and O. niloticus produced highly variable sex ratios, suggesting a complexity of hybrid sex determination. Few valid inferences could be made regarding intraspecific sex determination from these hybrid data. Sex ratios from progeny testing of sex-reversed males (1∶3) and most sex-reversed females (1∶0) provide evidence for female heterogamety in O. aureus. Several aberrant ratios observed suggest Mendelian inheritance of an autosomal recessive gene (F,f), epistatic to the major sex-determining gene (W,Z). Sex ratios of triploids and gynogens support the hypothesis of recombination between the centromere and the major sex-determining locus. Progeny testing of a female mitogyne demonstrated the viability of a novel WW “superfemale”, which gave only female offspring. Not all data could be explained by a two-factor model of sex determination. Further exceptional sex ratios may be accounted for by rare autosomal or environmental sex-modifying factors. It is concluded that O. aureus has a multifactorial mechanism of sex determination with the underlying primary mechanism of female heterogamety.

Key words

Sex determination Oreochromis aureus Gynogenesis Sex reversal Hybridisation 

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • G. C. Mair
    • 1
  • A. G. Scott
    • 1
  • D. J. Penman
    • 1
  • D. O. F. Skibinski
    • 1
  • J. A. Beardmore
    • 1
  1. 1.School of Biological Sciences, University College of SwanseaSwanseaUK
  2. 2.FAC/CLSU-UCS Tilapia Genetics Project, Freshwater Aquaculture Center, Central Luzon State UniversityMunoz, Nueva EcijaThe Philippines
  3. 3.Department of Pure and Applied Biology, University of ReadingAquatic Biology Research UnitReading, BerkshireUK
  4. 4.Institute of Aquaculture, University of StirlingStirlingUK

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