Prostaglandin F 2α drives female pheromone signaling in cichlids, revealing a basis for evolutionary divergence in olfactory signaling.

Pheromones play essential roles in reproduction in many species. Prostaglandin F 2α (PGF 2α ) acts as a female reproductive hormone and as a sex pheromone in some species. An olfactory receptor (OR) for PGF 2α was recently discovered in zebrafish, but this signaling pathway is evolutionarily labile. To understand the evolution of signals that attract males to fertile females, we used the African cichlid Astatotilapia burtoni and found that adult males strongly prefer fertile female odors. Injection of a prostaglandin synthesis inhibitor abolishes this attractivity of fertile females, indicating these hormones are necessary for pheromonal signaling. Unlike zebrafish, A. burtoni males are insensitive to PGF 2α , but they do exhibit strong preference for females injected with PGF 2α . This attractiveness is independent of the PGF 2α hormonal receptor Ptgfr, indicating that this pheromone signaling derives from PGF 2α metabolization into a yet-undiscovered pheromone. We further discovered that fish that are insensitive to PGF 2α lack an ortholog for the OR Or114 that zebrafish use to detect PGF 2α . These results indicate that PGF 2α itself does not directly induce male preference in cichlids. Rather, it plays a vital role that primes females to become attractive via an alternative male OR.