[2] The American mycologist and geneticist Albert Francis Blakeslee, discovered that some species of Mucorales were self-sterile (heterothallic), in which interactions of two strains, designated (+) and (-), being necessary for the initiation of sexual activity.

This interaction was found by Hans Burgeff of the University of Goettingen to be due to the exchange of low molecular weight substances that diffused through the substratum and atmosphere.

The elucidation of the hormonal control of sexual interaction in the Mucorales extends over 60 years and involved mycologists and biochemists from Germany, Italy, the Netherlands, UK and the USA.

In the next stage, septae are established to limit the developing zygospore from the vegetative mycelium and in this way the zygophores become suspensor hyphae and gametangia are formed.

Species specificity of these reactions is among others obtained by spatial segregation, physicochemical features of derivatives (volatility and light sensitivity), chemical modifications of trisporoids and transcriptional/posttranscriptional regulation.