Effect of thyroid hormones on the development of pharyngeal dentition in roach Rutilus rutilus (Cyprinidae,Cypriniformes)

Development of teeth on the pharyngeal bones of roach Rutilus rutilus and the effect of thyroid hormones on this development are investigated. The addition of exogenous triiodothyronine leads to accelerated development of the teeth, but the deficit of triiodothyronine (provoked by the addition of thiourea in the media) stimulates the retardation of this development. Change of developmental rate of the organism leads to change in the definitive state of the pharyngeal teeth formula. Owing to accelerated development, the number of teeth significantly decreases, and the formulas 5–5, 5–4, and 4–4 appear instead of the typical formula 6–5 in the control group and in the fish from natural populations. Retarded development of the organism leads to increased frequency of occurrence of the formula 6–6. The directed asymmetry in the numbers of pharyngeal teeth with the formula (6–5), most likely, is connected with different types of teeth development on the left and right pharyngeal bones.