A part of the fertilization process is a poorly defined thing usually referred to as "activation". Thirty years ago, as a young grad student, the best example of this phenomenon was in a species of poeciliid fish (live-bearers, or ovoviviparous cyprinodonts) from the Gulf coast area of mexico. In "the wild", it existed only as females, but they could reproduce by "activation" brought on by sperm delivery by a male of either of the two species thought to have been their "progenitor" species. There was apparently no addition of genetic materials from the "activating" male to the developing embryos. I must hasten to add that I am no longer "current" on the literature, and more "advanced" explanations my have come along in the interim. Fascinating stuff.