Oreochromis is a genus closely related to the famous genus Tilapia. Both genera are a part of the tribe Tilapiini in the family Cichlidae (cichlids). Nile tilapia (Oreochromis niloticus), Mozambique tilapia (Oreochromis mossambicus), Victoria tilapia (Oreochromis variabilis) and Singida tilapia (Oreochromis esculentus) are just a few examples of well known Oreochromis species. The name Oreochromis is derived from the Latin word for gold, aurum.
A lot of species that once were placed in the genus Tilapia has now been moved to Oreochromis. In everyday species, it is common to refer to members of both genera as tilapia fish and you will find a lot of popular food fishes in both of them. Oreochromis currently contains roughly 30 different described species, but this figure might increase in the future as more species are moved to Oreochromis from other genera. There are also undescribed species that most likely will be placed in Oreochromis once they are named and described by science.
Mitochondrial DNA (mtDNA) sequence analysis has been used to shed more light on the evolutionary history of the Tilapiini cichlids and detangle their intricate relationships but the results are difficult to interpret due to the high incidence of hybridization within this group. In addition to this, the high pace of evolution exhibited by these fishes makes it tricky for scientists to pick the most appropriate nuclear DNA sequence to study.
The results of mtDNA) sequence analysis do for instance indicate that Oreochromis auerus (Blue tilapia) and Oreochromis urolepis hornorum (Wami tilapia) might actually be more closely related to members of the genus Sarotherodon than to their fellow Oreochromis species, but we still do not know for sure if they ought to be moved or not. Mitochondrial DNA sequence analysis also indicates that the genus Oreochromis might be comprised of at least two different clades. (A clade is a taxonomic group consisting of a single common ancestor and all its descendants.)