Intraspecific Variation in the Pharyngeal Tooth Formulae of Some Cyprinid Fishes

Forty-two species of cyprinids were studied to determine the amount of intraspecific variation in their pharyngeal tooth formulae. Widely different degrees of variation were found to exist. The percentage of arches, in a given species, bearing variant half-formulae ranged from 0 to 49.2%. The 0,4-4,0 formula was almost invariable whereas most of the species with 0,5-5,0; 2,5-4,2; or 1,4-4,1 formulae exhibited small or intermediate amounts of variation. The 2,4-4,2 condition was the most variable with four species possessing high percentages (5.8% to 49.2%) of deviant halfformulae. Some of the variability in certain formulae was attributed to evolutionary trends tending to decrease the number of minor-row teeth or increase the number of major-row teeth. A functional mechanism influencing the trends was offered. Faulty tooth replacement was also thought to contribute to some of the variation encountered. Because of the variability in certain formulae, it is suggested that pharyngeal arch and tooth characteristics should also be included in species descriptions and keys.