Cichlids are the largest family of vertebrates and have a wide variety of pigment patterns, making them a favorite among aquarium hobbyists. In addition to its contemplative value for humans, coloration is of utmost importance for the life activity and evolution of the cichlid fish themselves. However, information about the causes and mechanisms underlying the formation of its diversity is scattered and sporadic.
Employees of our institute were able to show that one of the most important factors influencing the ontogenesis and evolution of the diversity of cichlid colors is the activity of the thyroid gland and the dynamics of the concentrations of thyroid hormones synthesized by the gland. This conclusion is based on results obtained from experimental work on two species of Neotropical cichlids (Amatitlania nigrofasciata and Cryptoheros spilurus). In particular, it was found that thyroid hormones have a direct effect on the temporal characteristics of ontogenesis of most pigment cell lines. Untimely changes in hormone concentrations (hyper- or hypothyroidism) often lead to irreversible consequences and the formation of coloration characteristic not of this species (Fig. 1), but of other species of phylogenetically close and distant Neotropical cichlids. Taken together with previously obtained data on the participation of thyroid hormones in the formation of phenotypic diversity of various groups of fish and amphibians, the results presented in this work provide important evidence of the key role of the hypothalamic-pituitary-thyroid axis in the evolution of vertebrates.
The work was published in the oldest scientific international journal «Journal of Experimental Biology» (SJR Q1). Denis V. Prazdnikov and Fedor N. Shkil (2023). The role of thyroid hormones in development of coloration of two species of Neotropical cichlids. J. Exp. Biol. 226 (14), jeb245710. https://doi.org/10.1242/jeb.245710