Sexuality in Achlya Ambisexualis

SUMMARY

A study of sexuality in A. ambisexualis shows that four sexual strains are represented among the isolates of that species: (1) pure ♂, (2) predominant ♂, (3) predominant ♀, and (4) ♀pure These strains are cross-fertile in all combinations. Plants of the two predominantly sexual strains are weakly self-fertile, and give either a ♂ or a ♀ reaction when mated, depending on the stronger sexual affinity of the mate. Plants of both predominant ♂ and ♀ strains have been shown capable of reacting simultaneously as ♂ and ♀ in different portions of their thalli. In this species sexual reversals are shown as strikingly as anywhere in the fungi.

The six sexual strains found in the various so-called hetero-thallic species may be expressed as all possible combinations of four sexual factors: M, dominant maleness; m, latent maleness; f, latent femaleness; and F, dominant femaleness. The combinations possible are: Mm, pure ♂ Mf, predominant ♂, but also capable of reacting as ♀ Fm, predominant ♀ capable of reacting as ♂ Ff, pure ♀; FM, homothallic, both sexes strong and balanced; and fm, sexually sterile, both sexes weak and balanced.

To differentiate this sexual situation from heterothallism as defined by Blakeslee, the term gynandromixis or gynandromictic sexuality has been suggested, implying the mixed sexual characters of the thalli of the various strains and the capacity of two of these strains to behave as ♂ and/or ♀.