Walter Salzburger, Ingo Braasch and Axel Meyer studied 19 cichlid species reared at Konstanz University. They discovered that a gene involved in producing yellow pigment cells in oval spots on the fishes' fins, known as egg-dummies, are found on the anal fins of the male fish and are crucial to mating.
The fish are known as maternal mouthbrooders because once the female has laid her eggs, she picks them up in her mouth, according to the background information in an article published in online open access journal BMC Biology.
According to the researchers, the female fish gets attracted by the egg-dummy markings believing them to be eggs, and approaches the male. When the female is close to the anal fin, the male discharges sperm into the female's mouth to fertilize the eggs.
The researchers have revealed that the gene involved in producing the egg-dummy markings is called the colony-stimulating factor 1 receptor a (or csf1ra). They have also shown that the gene was expressed in the egg-dummies of a distantly related species, in which the spots developed on the pectoral fins rather than the anal fins.
"The two kinds of independently evolved egg-dummies serve as a model system to test whether the same genetic pathways are involved in the morphogenesis of both types of dummies," say the authors.