The Experimental Heterochronies in a Green Terror Cichlid Andinoacara rivulatus (Teleostei: Cichlidae: Cichlasomatinae) Indicate a Role of Developmental Changes in the Cichlids Coloration Evolution

Cichlids (Teleostei; Cichlidae) display a high variability of coloration, a morphological characteristic playing an important role in the life and evolution of fishes. The heterochrony—alterations in the developmental timing and rate—has been suggested to be one of the key mechanisms underpinning evolution of the pigment patterns in cichlids. Here, we present the experimental data indicating that heterochronies have an important role to play in the diversification of the American cichlids coloration. The data were obtained in the experiments with the green terror cichlid, Andinoacara rivulatus (Cichlasomatinae). The experimental heterochronies were induced by the manipulations with the level of the thyroid hormones, the crucial regulators of the developmental rate and timing in the lower vertebrates. We revealed: (i) the adult coloration of A. rivulatus is determined by the timing and rate of the pigment patterning; and (ii) the experimental heterochronies result in the appearance of the phenotypes mimicking the phenotypes typical of the various Cichlasomatinae species. These findings support the hypothetical role of heterochronies in the evolution of the American cichlids color pattern. Moreover, the revealed dependence of the cichlids pigment patterning on the thyroid axis activity offers the prospect for studying the role of the endocrine system in the evolution of bony fishes.