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

Authors

  • G. C. Mair
    • School of Biological Sciences, University College of Swansea
  • A. G. Scott
    • School of Biological Sciences, University College of Swansea
  • D. J. Penman
    • School of Biological Sciences, University College of Swansea
  • D. O. F. Skibinski
    • School of Biological Sciences, University College of Swansea
  • J. A. Beardmore
    • School of Biological Sciences, University College of Swansea
Originals

DOI: 10.1007/BF00226206

Cite this article as:
Mair, G.C., Scott, A.G., Penman, D.J. et al. Theoret. Appl. Genetics (1991) 82: 153. doi:10.1007/BF00226206

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 determinationOreochromis aureusGynogenesisSex reversalHybridisation

Copyright information

© Springer-Verlag 1991