Sex hormones of the aquatic fungusAchlya.

Fungi in the order Saprolegniales are known to contain varying proportions of sterols, such as cholesterol and fucosterol. In the caseAchyla, it has been found that fucosterol, the major sterol component, serves as the biosynthetic precursor of the hormones, antheriodiol and the oogoniols. Antheridiol is secreted by female strains ofAchlya and induces the formation of antheridial hyphae in male strains. It also causes the male to secrete the oogoniols which induce the formation of oogonial initials in female strains. Antheriodiol is responsible for the chemotropic growth of the antheridial hyphae to a developing oogonium which results in sexual conjugation. The structures, biosynthesis, and functions of these hormones are discussed in this paper.