Rio Grande (Bravo) and Soto la Marina drainage systems in northeastern México wihthold two different but closely related cichlid species, namely Herichthys cyanoguttatus and Herichthys carpintis. The distance between northern and southern affluents of these rivers is no more than 5 km. away, although a small geographical accident lays between them. This article explores how is the change in appearence between the two species, is there an abrupt or gradual change between them? How far how they radiated in evolutive terms?.
A survey for the Turquoise Herichthys forms of Rio Pantepec and Cazones river systems in Eastern Mexico.