Prolactin Gene Duplication within the Family Cichilidae

The prolactin gene has undergone a duplication event within the cichlid lineage, producing two distinct forms of prolactin (PRL188 and PRL177). The hormone prolactin is critical for regulating parental care in many species. Cichlid fishes exhibit a wide variety of parental care strategies, including maternal-only, paternal-only, and biparental care. A recent study found evidence for positive selection acting on the duplicate prolactin gene (PRL177), suggesting that this duplication event was associated with the evolution of alternative mating strategies. Polymerase chain reaction was used to isolate and amplify genes for both prolactin hormones and two prolactin receptors from brain derived cDNAs from species in the Ectodini and Tilapiine lineages. To date, a total of 43 species have been surveyed with PRL 188 having been amplified in 29 species, PRL 177 from 12 species, PRLR I from 15 species and PRLR II from 33 species. I was able to amplify PRL 177 in Ectodini lineage, indicating that it is not Tilapiine specific. I also discovered an unexpected rate of sequence divergence of the PRLR II gene in the Ectodini lineage. In this study, I examine the evolution of prolactin genes within the family Cichlidae which exhibit multiple forms of parental care. I hypothesize that PRL 177 should be present throughout the cichlid family.