Variability in the number of tooth rows in the pharyngeal dentition of<i>Barbus intermedius</i>(Teleostei; Cyprinidae): genetic, hormonal and environmental factors

Abstract

The variability of pharyngeal dentition in a natural population of B. intermedius and effects of genetic, hormonal and environmental factors on the number of tooth rows in the pharyngeal dentition in offspring from wild-caught parents have been investigated. It was revealed that: (i) about 10% of fish from natural population have four-rowed dentition instead of three-rowed dentition characteristic for this species; (ii) the presence of the additional tooth row is not an abnormality of tooth replacement since it occurs symmetrically on both sides; (iii) occurrence of the fourth row of teeth is heritable since laboratory-reared offspring from parents with four-rowed dentition have the same dentition. Even if one of the parents had four-rowed dentition the percentage of four-rowed individuals in the progeny was significantly higher than in progeny from parents with normal (three rowed) dentition; (iv) the number of tooth rows appears to be hormonally controlled: high levels of thyroid hormone result in a decrease in the number of tooth rows to two. In contrast, deficiency of this hormone results in an increase to four rows; (v) no differences in the number of tooth rows were found in fish reared under 17°C, 24°C, 30°C and room temperature (20–26°C).