Bioassay-driven purification of pheromones mediating mate choice in guppies (Poecilia reticulata).

Behavioural choice tests in a Y-maze flume have demonstrated that female guppies Poecilia reticulate are only marginally attracted by olfactory cues from conspecifics. Moreover, the small size of female guppies makes quite challenging the recording of electro-olfactograms (EOG) underlying the identification of fish chemical cues. Therefore, the British and Portuguese team members agreed to change the initial scope of the project. In cichlids, choice tests on Pseudotropheus emmiltos demonstrated that females spawned preferably next to conspecific males only when olfactory cues were present. In the absence of olfactory cues, females showed no preference between conspecific and heterospecific males (P. fainzilberi) and spawned equally with either species. These novel results suggest that divergence of olfactory signals may lead to reproductive isolation and consequently to speciation in cichlids.